linux/fs/exec.c
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   1/*
   2 *  linux/fs/exec.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 */
   6
   7/*
   8 * #!-checking implemented by tytso.
   9 */
  10/*
  11 * Demand-loading implemented 01.12.91 - no need to read anything but
  12 * the header into memory. The inode of the executable is put into
  13 * "current->executable", and page faults do the actual loading. Clean.
  14 *
  15 * Once more I can proudly say that linux stood up to being changed: it
  16 * was less than 2 hours work to get demand-loading completely implemented.
  17 *
  18 * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19 * current->executable is only used by the procfs.  This allows a dispatch
  20 * table to check for several different types  of binary formats.  We keep
  21 * trying until we recognize the file or we run out of supported binary
  22 * formats. 
  23 */
  24
  25#include <linux/slab.h>
  26#include <linux/file.h>
  27#include <linux/fdtable.h>
  28#include <linux/mm.h>
  29#include <linux/stat.h>
  30#include <linux/fcntl.h>
  31#include <linux/swap.h>
  32#include <linux/string.h>
  33#include <linux/init.h>
  34#include <linux/pagemap.h>
  35#include <linux/perf_event.h>
  36#include <linux/highmem.h>
  37#include <linux/spinlock.h>
  38#include <linux/key.h>
  39#include <linux/personality.h>
  40#include <linux/binfmts.h>
  41#include <linux/utsname.h>
  42#include <linux/pid_namespace.h>
  43#include <linux/module.h>
  44#include <linux/namei.h>
  45#include <linux/proc_fs.h>
  46#include <linux/mount.h>
  47#include <linux/security.h>
  48#include <linux/syscalls.h>
  49#include <linux/tsacct_kern.h>
  50#include <linux/cn_proc.h>
  51#include <linux/audit.h>
  52#include <linux/tracehook.h>
  53#include <linux/kmod.h>
  54#include <linux/fsnotify.h>
  55#include <linux/fs_struct.h>
  56#include <linux/pipe_fs_i.h>
  57#include <linux/oom.h>
  58
  59#include <asm/uaccess.h>
  60#include <asm/mmu_context.h>
  61#include <asm/tlb.h>
  62#include "internal.h"
  63
  64int core_uses_pid;
  65char core_pattern[CORENAME_MAX_SIZE] = "core";
  66unsigned int core_pipe_limit;
  67int suid_dumpable = 0;
  68
  69struct core_name {
  70        char *corename;
  71        int used, size;
  72};
  73static atomic_t call_count = ATOMIC_INIT(1);
  74
  75/* The maximal length of core_pattern is also specified in sysctl.c */
  76
  77static LIST_HEAD(formats);
  78static DEFINE_RWLOCK(binfmt_lock);
  79
  80int __register_binfmt(struct linux_binfmt * fmt, int insert)
  81{
  82        if (!fmt)
  83                return -EINVAL;
  84        write_lock(&binfmt_lock);
  85        insert ? list_add(&fmt->lh, &formats) :
  86                 list_add_tail(&fmt->lh, &formats);
  87        write_unlock(&binfmt_lock);
  88        return 0;       
  89}
  90
  91EXPORT_SYMBOL(__register_binfmt);
  92
  93void unregister_binfmt(struct linux_binfmt * fmt)
  94{
  95        write_lock(&binfmt_lock);
  96        list_del(&fmt->lh);
  97        write_unlock(&binfmt_lock);
  98}
  99
 100EXPORT_SYMBOL(unregister_binfmt);
 101
 102static inline void put_binfmt(struct linux_binfmt * fmt)
 103{
 104        module_put(fmt->module);
 105}
 106
 107/*
 108 * Note that a shared library must be both readable and executable due to
 109 * security reasons.
 110 *
 111 * Also note that we take the address to load from from the file itself.
 112 */
 113SYSCALL_DEFINE1(uselib, const char __user *, library)
 114{
 115        struct file *file;
 116        char *tmp = getname(library);
 117        int error = PTR_ERR(tmp);
 118
 119        if (IS_ERR(tmp))
 120                goto out;
 121
 122        file = do_filp_open(AT_FDCWD, tmp,
 123                                O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
 124                                MAY_READ | MAY_EXEC | MAY_OPEN);
 125        putname(tmp);
 126        error = PTR_ERR(file);
 127        if (IS_ERR(file))
 128                goto out;
 129
 130        error = -EINVAL;
 131        if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 132                goto exit;
 133
 134        error = -EACCES;
 135        if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 136                goto exit;
 137
 138        fsnotify_open(file);
 139
 140        error = -ENOEXEC;
 141        if(file->f_op) {
 142                struct linux_binfmt * fmt;
 143
 144                read_lock(&binfmt_lock);
 145                list_for_each_entry(fmt, &formats, lh) {
 146                        if (!fmt->load_shlib)
 147                                continue;
 148                        if (!try_module_get(fmt->module))
 149                                continue;
 150                        read_unlock(&binfmt_lock);
 151                        error = fmt->load_shlib(file);
 152                        read_lock(&binfmt_lock);
 153                        put_binfmt(fmt);
 154                        if (error != -ENOEXEC)
 155                                break;
 156                }
 157                read_unlock(&binfmt_lock);
 158        }
 159exit:
 160        fput(file);
 161out:
 162        return error;
 163}
 164
 165#ifdef CONFIG_MMU
 166
 167void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 168{
 169        struct mm_struct *mm = current->mm;
 170        long diff = (long)(pages - bprm->vma_pages);
 171
 172        if (!mm || !diff)
 173                return;
 174
 175        bprm->vma_pages = pages;
 176
 177#ifdef SPLIT_RSS_COUNTING
 178        add_mm_counter(mm, MM_ANONPAGES, diff);
 179#else
 180        spin_lock(&mm->page_table_lock);
 181        add_mm_counter(mm, MM_ANONPAGES, diff);
 182        spin_unlock(&mm->page_table_lock);
 183#endif
 184}
 185
 186struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 187                int write)
 188{
 189        struct page *page;
 190        int ret;
 191
 192#ifdef CONFIG_STACK_GROWSUP
 193        if (write) {
 194                ret = expand_stack_downwards(bprm->vma, pos);
 195                if (ret < 0)
 196                        return NULL;
 197        }
 198#endif
 199        ret = get_user_pages(current, bprm->mm, pos,
 200                        1, write, 1, &page, NULL);
 201        if (ret <= 0)
 202                return NULL;
 203
 204        if (write) {
 205                unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 206                struct rlimit *rlim;
 207
 208                acct_arg_size(bprm, size / PAGE_SIZE);
 209
 210                /*
 211                 * We've historically supported up to 32 pages (ARG_MAX)
 212                 * of argument strings even with small stacks
 213                 */
 214                if (size <= ARG_MAX)
 215                        return page;
 216
 217                /*
 218                 * Limit to 1/4-th the stack size for the argv+env strings.
 219                 * This ensures that:
 220                 *  - the remaining binfmt code will not run out of stack space,
 221                 *  - the program will have a reasonable amount of stack left
 222                 *    to work from.
 223                 */
 224                rlim = current->signal->rlim;
 225                if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 226                        put_page(page);
 227                        return NULL;
 228                }
 229        }
 230
 231        return page;
 232}
 233
 234static void put_arg_page(struct page *page)
 235{
 236        put_page(page);
 237}
 238
 239static void free_arg_page(struct linux_binprm *bprm, int i)
 240{
 241}
 242
 243static void free_arg_pages(struct linux_binprm *bprm)
 244{
 245}
 246
 247static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 248                struct page *page)
 249{
 250        flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 251}
 252
 253static int __bprm_mm_init(struct linux_binprm *bprm)
 254{
 255        int err;
 256        struct vm_area_struct *vma = NULL;
 257        struct mm_struct *mm = bprm->mm;
 258
 259        bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 260        if (!vma)
 261                return -ENOMEM;
 262
 263        down_write(&mm->mmap_sem);
 264        vma->vm_mm = mm;
 265
 266        /*
 267         * Place the stack at the largest stack address the architecture
 268         * supports. Later, we'll move this to an appropriate place. We don't
 269         * use STACK_TOP because that can depend on attributes which aren't
 270         * configured yet.
 271         */
 272        BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 273        vma->vm_end = STACK_TOP_MAX;
 274        vma->vm_start = vma->vm_end - PAGE_SIZE;
 275        vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 276        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 277        INIT_LIST_HEAD(&vma->anon_vma_chain);
 278
 279        err = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1);
 280        if (err)
 281                goto err;
 282
 283        err = insert_vm_struct(mm, vma);
 284        if (err)
 285                goto err;
 286
 287        mm->stack_vm = mm->total_vm = 1;
 288        up_write(&mm->mmap_sem);
 289        bprm->p = vma->vm_end - sizeof(void *);
 290        return 0;
 291err:
 292        up_write(&mm->mmap_sem);
 293        bprm->vma = NULL;
 294        kmem_cache_free(vm_area_cachep, vma);
 295        return err;
 296}
 297
 298static bool valid_arg_len(struct linux_binprm *bprm, long len)
 299{
 300        return len <= MAX_ARG_STRLEN;
 301}
 302
 303#else
 304
 305void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 306{
 307}
 308
 309struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 310                int write)
 311{
 312        struct page *page;
 313
 314        page = bprm->page[pos / PAGE_SIZE];
 315        if (!page && write) {
 316                page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 317                if (!page)
 318                        return NULL;
 319                bprm->page[pos / PAGE_SIZE] = page;
 320        }
 321
 322        return page;
 323}
 324
 325static void put_arg_page(struct page *page)
 326{
 327}
 328
 329static void free_arg_page(struct linux_binprm *bprm, int i)
 330{
 331        if (bprm->page[i]) {
 332                __free_page(bprm->page[i]);
 333                bprm->page[i] = NULL;
 334        }
 335}
 336
 337static void free_arg_pages(struct linux_binprm *bprm)
 338{
 339        int i;
 340
 341        for (i = 0; i < MAX_ARG_PAGES; i++)
 342                free_arg_page(bprm, i);
 343}
 344
 345static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 346                struct page *page)
 347{
 348}
 349
 350static int __bprm_mm_init(struct linux_binprm *bprm)
 351{
 352        bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 353        return 0;
 354}
 355
 356static bool valid_arg_len(struct linux_binprm *bprm, long len)
 357{
 358        return len <= bprm->p;
 359}
 360
 361#endif /* CONFIG_MMU */
 362
 363/*
 364 * Create a new mm_struct and populate it with a temporary stack
 365 * vm_area_struct.  We don't have enough context at this point to set the stack
 366 * flags, permissions, and offset, so we use temporary values.  We'll update
 367 * them later in setup_arg_pages().
 368 */
 369int bprm_mm_init(struct linux_binprm *bprm)
 370{
 371        int err;
 372        struct mm_struct *mm = NULL;
 373
 374        bprm->mm = mm = mm_alloc();
 375        err = -ENOMEM;
 376        if (!mm)
 377                goto err;
 378
 379        err = init_new_context(current, mm);
 380        if (err)
 381                goto err;
 382
 383        err = __bprm_mm_init(bprm);
 384        if (err)
 385                goto err;
 386
 387        return 0;
 388
 389err:
 390        if (mm) {
 391                bprm->mm = NULL;
 392                mmdrop(mm);
 393        }
 394
 395        return err;
 396}
 397
 398/*
 399 * count() counts the number of strings in array ARGV.
 400 */
 401static int count(const char __user * const __user * argv, int max)
 402{
 403        int i = 0;
 404
 405        if (argv != NULL) {
 406                for (;;) {
 407                        const char __user * p;
 408
 409                        if (get_user(p, argv))
 410                                return -EFAULT;
 411                        if (!p)
 412                                break;
 413                        argv++;
 414                        if (i++ >= max)
 415                                return -E2BIG;
 416
 417                        if (fatal_signal_pending(current))
 418                                return -ERESTARTNOHAND;
 419                        cond_resched();
 420                }
 421        }
 422        return i;
 423}
 424
 425/*
 426 * 'copy_strings()' copies argument/environment strings from the old
 427 * processes's memory to the new process's stack.  The call to get_user_pages()
 428 * ensures the destination page is created and not swapped out.
 429 */
 430static int copy_strings(int argc, const char __user *const __user *argv,
 431                        struct linux_binprm *bprm)
 432{
 433        struct page *kmapped_page = NULL;
 434        char *kaddr = NULL;
 435        unsigned long kpos = 0;
 436        int ret;
 437
 438        while (argc-- > 0) {
 439                const char __user *str;
 440                int len;
 441                unsigned long pos;
 442
 443                if (get_user(str, argv+argc) ||
 444                                !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
 445                        ret = -EFAULT;
 446                        goto out;
 447                }
 448
 449                if (!valid_arg_len(bprm, len)) {
 450                        ret = -E2BIG;
 451                        goto out;
 452                }
 453
 454                /* We're going to work our way backwords. */
 455                pos = bprm->p;
 456                str += len;
 457                bprm->p -= len;
 458
 459                while (len > 0) {
 460                        int offset, bytes_to_copy;
 461
 462                        if (fatal_signal_pending(current)) {
 463                                ret = -ERESTARTNOHAND;
 464                                goto out;
 465                        }
 466                        cond_resched();
 467
 468                        offset = pos % PAGE_SIZE;
 469                        if (offset == 0)
 470                                offset = PAGE_SIZE;
 471
 472                        bytes_to_copy = offset;
 473                        if (bytes_to_copy > len)
 474                                bytes_to_copy = len;
 475
 476                        offset -= bytes_to_copy;
 477                        pos -= bytes_to_copy;
 478                        str -= bytes_to_copy;
 479                        len -= bytes_to_copy;
 480
 481                        if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 482                                struct page *page;
 483
 484                                page = get_arg_page(bprm, pos, 1);
 485                                if (!page) {
 486                                        ret = -E2BIG;
 487                                        goto out;
 488                                }
 489
 490                                if (kmapped_page) {
 491                                        flush_kernel_dcache_page(kmapped_page);
 492                                        kunmap(kmapped_page);
 493                                        put_arg_page(kmapped_page);
 494                                }
 495                                kmapped_page = page;
 496                                kaddr = kmap(kmapped_page);
 497                                kpos = pos & PAGE_MASK;
 498                                flush_arg_page(bprm, kpos, kmapped_page);
 499                        }
 500                        if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 501                                ret = -EFAULT;
 502                                goto out;
 503                        }
 504                }
 505        }
 506        ret = 0;
 507out:
 508        if (kmapped_page) {
 509                flush_kernel_dcache_page(kmapped_page);
 510                kunmap(kmapped_page);
 511                put_arg_page(kmapped_page);
 512        }
 513        return ret;
 514}
 515
 516/*
 517 * Like copy_strings, but get argv and its values from kernel memory.
 518 */
 519int copy_strings_kernel(int argc, const char *const *argv,
 520                        struct linux_binprm *bprm)
 521{
 522        int r;
 523        mm_segment_t oldfs = get_fs();
 524        set_fs(KERNEL_DS);
 525        r = copy_strings(argc, (const char __user *const  __user *)argv, bprm);
 526        set_fs(oldfs);
 527        return r;
 528}
 529EXPORT_SYMBOL(copy_strings_kernel);
 530
 531#ifdef CONFIG_MMU
 532
 533/*
 534 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 535 * the binfmt code determines where the new stack should reside, we shift it to
 536 * its final location.  The process proceeds as follows:
 537 *
 538 * 1) Use shift to calculate the new vma endpoints.
 539 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 540 *    arguments passed to subsequent functions are consistent.
 541 * 3) Move vma's page tables to the new range.
 542 * 4) Free up any cleared pgd range.
 543 * 5) Shrink the vma to cover only the new range.
 544 */
 545static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 546{
 547        struct mm_struct *mm = vma->vm_mm;
 548        unsigned long old_start = vma->vm_start;
 549        unsigned long old_end = vma->vm_end;
 550        unsigned long length = old_end - old_start;
 551        unsigned long new_start = old_start - shift;
 552        unsigned long new_end = old_end - shift;
 553        struct mmu_gather *tlb;
 554
 555        BUG_ON(new_start > new_end);
 556
 557        /*
 558         * ensure there are no vmas between where we want to go
 559         * and where we are
 560         */
 561        if (vma != find_vma(mm, new_start))
 562                return -EFAULT;
 563
 564        /*
 565         * cover the whole range: [new_start, old_end)
 566         */
 567        if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 568                return -ENOMEM;
 569
 570        /*
 571         * move the page tables downwards, on failure we rely on
 572         * process cleanup to remove whatever mess we made.
 573         */
 574        if (length != move_page_tables(vma, old_start,
 575                                       vma, new_start, length))
 576                return -ENOMEM;
 577
 578        lru_add_drain();
 579        tlb = tlb_gather_mmu(mm, 0);
 580        if (new_end > old_start) {
 581                /*
 582                 * when the old and new regions overlap clear from new_end.
 583                 */
 584                free_pgd_range(tlb, new_end, old_end, new_end,
 585                        vma->vm_next ? vma->vm_next->vm_start : 0);
 586        } else {
 587                /*
 588                 * otherwise, clean from old_start; this is done to not touch
 589                 * the address space in [new_end, old_start) some architectures
 590                 * have constraints on va-space that make this illegal (IA64) -
 591                 * for the others its just a little faster.
 592                 */
 593                free_pgd_range(tlb, old_start, old_end, new_end,
 594                        vma->vm_next ? vma->vm_next->vm_start : 0);
 595        }
 596        tlb_finish_mmu(tlb, new_end, old_end);
 597
 598        /*
 599         * Shrink the vma to just the new range.  Always succeeds.
 600         */
 601        vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 602
 603        return 0;
 604}
 605
 606/*
 607 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 608 * the stack is optionally relocated, and some extra space is added.
 609 */
 610int setup_arg_pages(struct linux_binprm *bprm,
 611                    unsigned long stack_top,
 612                    int executable_stack)
 613{
 614        unsigned long ret;
 615        unsigned long stack_shift;
 616        struct mm_struct *mm = current->mm;
 617        struct vm_area_struct *vma = bprm->vma;
 618        struct vm_area_struct *prev = NULL;
 619        unsigned long vm_flags;
 620        unsigned long stack_base;
 621        unsigned long stack_size;
 622        unsigned long stack_expand;
 623        unsigned long rlim_stack;
 624
 625#ifdef CONFIG_STACK_GROWSUP
 626        /* Limit stack size to 1GB */
 627        stack_base = rlimit_max(RLIMIT_STACK);
 628        if (stack_base > (1 << 30))
 629                stack_base = 1 << 30;
 630
 631        /* Make sure we didn't let the argument array grow too large. */
 632        if (vma->vm_end - vma->vm_start > stack_base)
 633                return -ENOMEM;
 634
 635        stack_base = PAGE_ALIGN(stack_top - stack_base);
 636
 637        stack_shift = vma->vm_start - stack_base;
 638        mm->arg_start = bprm->p - stack_shift;
 639        bprm->p = vma->vm_end - stack_shift;
 640#else
 641        stack_top = arch_align_stack(stack_top);
 642        stack_top = PAGE_ALIGN(stack_top);
 643
 644        if (unlikely(stack_top < mmap_min_addr) ||
 645            unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 646                return -ENOMEM;
 647
 648        stack_shift = vma->vm_end - stack_top;
 649
 650        bprm->p -= stack_shift;
 651        mm->arg_start = bprm->p;
 652#endif
 653
 654        if (bprm->loader)
 655                bprm->loader -= stack_shift;
 656        bprm->exec -= stack_shift;
 657
 658        down_write(&mm->mmap_sem);
 659        vm_flags = VM_STACK_FLAGS;
 660
 661        /*
 662         * Adjust stack execute permissions; explicitly enable for
 663         * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 664         * (arch default) otherwise.
 665         */
 666        if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 667                vm_flags |= VM_EXEC;
 668        else if (executable_stack == EXSTACK_DISABLE_X)
 669                vm_flags &= ~VM_EXEC;
 670        vm_flags |= mm->def_flags;
 671        vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 672
 673        ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 674                        vm_flags);
 675        if (ret)
 676                goto out_unlock;
 677        BUG_ON(prev != vma);
 678
 679        /* Move stack pages down in memory. */
 680        if (stack_shift) {
 681                ret = shift_arg_pages(vma, stack_shift);
 682                if (ret)
 683                        goto out_unlock;
 684        }
 685
 686        /* mprotect_fixup is overkill to remove the temporary stack flags */
 687        vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 688
 689        stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 690        stack_size = vma->vm_end - vma->vm_start;
 691        /*
 692         * Align this down to a page boundary as expand_stack
 693         * will align it up.
 694         */
 695        rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 696#ifdef CONFIG_STACK_GROWSUP
 697        if (stack_size + stack_expand > rlim_stack)
 698                stack_base = vma->vm_start + rlim_stack;
 699        else
 700                stack_base = vma->vm_end + stack_expand;
 701#else
 702        if (stack_size + stack_expand > rlim_stack)
 703                stack_base = vma->vm_end - rlim_stack;
 704        else
 705                stack_base = vma->vm_start - stack_expand;
 706#endif
 707        current->mm->start_stack = bprm->p;
 708        ret = expand_stack(vma, stack_base);
 709        if (ret)
 710                ret = -EFAULT;
 711
 712out_unlock:
 713        up_write(&mm->mmap_sem);
 714        return ret;
 715}
 716EXPORT_SYMBOL(setup_arg_pages);
 717
 718#endif /* CONFIG_MMU */
 719
 720struct file *open_exec(const char *name)
 721{
 722        struct file *file;
 723        int err;
 724
 725        file = do_filp_open(AT_FDCWD, name,
 726                                O_LARGEFILE | O_RDONLY | FMODE_EXEC, 0,
 727                                MAY_EXEC | MAY_OPEN);
 728        if (IS_ERR(file))
 729                goto out;
 730
 731        err = -EACCES;
 732        if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 733                goto exit;
 734
 735        if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 736                goto exit;
 737
 738        fsnotify_open(file);
 739
 740        err = deny_write_access(file);
 741        if (err)
 742                goto exit;
 743
 744out:
 745        return file;
 746
 747exit:
 748        fput(file);
 749        return ERR_PTR(err);
 750}
 751EXPORT_SYMBOL(open_exec);
 752
 753int kernel_read(struct file *file, loff_t offset,
 754                char *addr, unsigned long count)
 755{
 756        mm_segment_t old_fs;
 757        loff_t pos = offset;
 758        int result;
 759
 760        old_fs = get_fs();
 761        set_fs(get_ds());
 762        /* The cast to a user pointer is valid due to the set_fs() */
 763        result = vfs_read(file, (void __user *)addr, count, &pos);
 764        set_fs(old_fs);
 765        return result;
 766}
 767
 768EXPORT_SYMBOL(kernel_read);
 769
 770static int exec_mmap(struct mm_struct *mm)
 771{
 772        struct task_struct *tsk;
 773        struct mm_struct * old_mm, *active_mm;
 774
 775        /* Notify parent that we're no longer interested in the old VM */
 776        tsk = current;
 777        old_mm = current->mm;
 778        sync_mm_rss(tsk, old_mm);
 779        mm_release(tsk, old_mm);
 780
 781        if (old_mm) {
 782                /*
 783                 * Make sure that if there is a core dump in progress
 784                 * for the old mm, we get out and die instead of going
 785                 * through with the exec.  We must hold mmap_sem around
 786                 * checking core_state and changing tsk->mm.
 787                 */
 788                down_read(&old_mm->mmap_sem);
 789                if (unlikely(old_mm->core_state)) {
 790                        up_read(&old_mm->mmap_sem);
 791                        return -EINTR;
 792                }
 793        }
 794        task_lock(tsk);
 795        active_mm = tsk->active_mm;
 796        tsk->mm = mm;
 797        tsk->active_mm = mm;
 798        activate_mm(active_mm, mm);
 799        if (old_mm && tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
 800                atomic_dec(&old_mm->oom_disable_count);
 801                atomic_inc(&tsk->mm->oom_disable_count);
 802        }
 803        task_unlock(tsk);
 804        arch_pick_mmap_layout(mm);
 805        if (old_mm) {
 806                up_read(&old_mm->mmap_sem);
 807                BUG_ON(active_mm != old_mm);
 808                mm_update_next_owner(old_mm);
 809                mmput(old_mm);
 810                return 0;
 811        }
 812        mmdrop(active_mm);
 813        return 0;
 814}
 815
 816/*
 817 * This function makes sure the current process has its own signal table,
 818 * so that flush_signal_handlers can later reset the handlers without
 819 * disturbing other processes.  (Other processes might share the signal
 820 * table via the CLONE_SIGHAND option to clone().)
 821 */
 822static int de_thread(struct task_struct *tsk)
 823{
 824        struct signal_struct *sig = tsk->signal;
 825        struct sighand_struct *oldsighand = tsk->sighand;
 826        spinlock_t *lock = &oldsighand->siglock;
 827
 828        if (thread_group_empty(tsk))
 829                goto no_thread_group;
 830
 831        /*
 832         * Kill all other threads in the thread group.
 833         */
 834        spin_lock_irq(lock);
 835        if (signal_group_exit(sig)) {
 836                /*
 837                 * Another group action in progress, just
 838                 * return so that the signal is processed.
 839                 */
 840                spin_unlock_irq(lock);
 841                return -EAGAIN;
 842        }
 843
 844        sig->group_exit_task = tsk;
 845        sig->notify_count = zap_other_threads(tsk);
 846        if (!thread_group_leader(tsk))
 847                sig->notify_count--;
 848
 849        while (sig->notify_count) {
 850                __set_current_state(TASK_UNINTERRUPTIBLE);
 851                spin_unlock_irq(lock);
 852                schedule();
 853                spin_lock_irq(lock);
 854        }
 855        spin_unlock_irq(lock);
 856
 857        /*
 858         * At this point all other threads have exited, all we have to
 859         * do is to wait for the thread group leader to become inactive,
 860         * and to assume its PID:
 861         */
 862        if (!thread_group_leader(tsk)) {
 863                struct task_struct *leader = tsk->group_leader;
 864
 865                sig->notify_count = -1; /* for exit_notify() */
 866                for (;;) {
 867                        write_lock_irq(&tasklist_lock);
 868                        if (likely(leader->exit_state))
 869                                break;
 870                        __set_current_state(TASK_UNINTERRUPTIBLE);
 871                        write_unlock_irq(&tasklist_lock);
 872                        schedule();
 873                }
 874
 875                /*
 876                 * The only record we have of the real-time age of a
 877                 * process, regardless of execs it's done, is start_time.
 878                 * All the past CPU time is accumulated in signal_struct
 879                 * from sister threads now dead.  But in this non-leader
 880                 * exec, nothing survives from the original leader thread,
 881                 * whose birth marks the true age of this process now.
 882                 * When we take on its identity by switching to its PID, we
 883                 * also take its birthdate (always earlier than our own).
 884                 */
 885                tsk->start_time = leader->start_time;
 886
 887                BUG_ON(!same_thread_group(leader, tsk));
 888                BUG_ON(has_group_leader_pid(tsk));
 889                /*
 890                 * An exec() starts a new thread group with the
 891                 * TGID of the previous thread group. Rehash the
 892                 * two threads with a switched PID, and release
 893                 * the former thread group leader:
 894                 */
 895
 896                /* Become a process group leader with the old leader's pid.
 897                 * The old leader becomes a thread of the this thread group.
 898                 * Note: The old leader also uses this pid until release_task
 899                 *       is called.  Odd but simple and correct.
 900                 */
 901                detach_pid(tsk, PIDTYPE_PID);
 902                tsk->pid = leader->pid;
 903                attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 904                transfer_pid(leader, tsk, PIDTYPE_PGID);
 905                transfer_pid(leader, tsk, PIDTYPE_SID);
 906
 907                list_replace_rcu(&leader->tasks, &tsk->tasks);
 908                list_replace_init(&leader->sibling, &tsk->sibling);
 909
 910                tsk->group_leader = tsk;
 911                leader->group_leader = tsk;
 912
 913                tsk->exit_signal = SIGCHLD;
 914
 915                BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 916                leader->exit_state = EXIT_DEAD;
 917                write_unlock_irq(&tasklist_lock);
 918
 919                release_task(leader);
 920        }
 921
 922        sig->group_exit_task = NULL;
 923        sig->notify_count = 0;
 924
 925no_thread_group:
 926        if (current->mm)
 927                setmax_mm_hiwater_rss(&sig->maxrss, current->mm);
 928
 929        exit_itimers(sig);
 930        flush_itimer_signals();
 931
 932        if (atomic_read(&oldsighand->count) != 1) {
 933                struct sighand_struct *newsighand;
 934                /*
 935                 * This ->sighand is shared with the CLONE_SIGHAND
 936                 * but not CLONE_THREAD task, switch to the new one.
 937                 */
 938                newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 939                if (!newsighand)
 940                        return -ENOMEM;
 941
 942                atomic_set(&newsighand->count, 1);
 943                memcpy(newsighand->action, oldsighand->action,
 944                       sizeof(newsighand->action));
 945
 946                write_lock_irq(&tasklist_lock);
 947                spin_lock(&oldsighand->siglock);
 948                rcu_assign_pointer(tsk->sighand, newsighand);
 949                spin_unlock(&oldsighand->siglock);
 950                write_unlock_irq(&tasklist_lock);
 951
 952                __cleanup_sighand(oldsighand);
 953        }
 954
 955        BUG_ON(!thread_group_leader(tsk));
 956        return 0;
 957}
 958
 959/*
 960 * These functions flushes out all traces of the currently running executable
 961 * so that a new one can be started
 962 */
 963static void flush_old_files(struct files_struct * files)
 964{
 965        long j = -1;
 966        struct fdtable *fdt;
 967
 968        spin_lock(&files->file_lock);
 969        for (;;) {
 970                unsigned long set, i;
 971
 972                j++;
 973                i = j * __NFDBITS;
 974                fdt = files_fdtable(files);
 975                if (i >= fdt->max_fds)
 976                        break;
 977                set = fdt->close_on_exec->fds_bits[j];
 978                if (!set)
 979                        continue;
 980                fdt->close_on_exec->fds_bits[j] = 0;
 981                spin_unlock(&files->file_lock);
 982                for ( ; set ; i++,set >>= 1) {
 983                        if (set & 1) {
 984                                sys_close(i);
 985                        }
 986                }
 987                spin_lock(&files->file_lock);
 988
 989        }
 990        spin_unlock(&files->file_lock);
 991}
 992
 993char *get_task_comm(char *buf, struct task_struct *tsk)
 994{
 995        /* buf must be at least sizeof(tsk->comm) in size */
 996        task_lock(tsk);
 997        strncpy(buf, tsk->comm, sizeof(tsk->comm));
 998        task_unlock(tsk);
 999        return buf;
1000}
1001
1002void set_task_comm(struct task_struct *tsk, char *buf)
1003{
1004        task_lock(tsk);
1005
1006        /*
1007         * Threads may access current->comm without holding
1008         * the task lock, so write the string carefully.
1009         * Readers without a lock may see incomplete new
1010         * names but are safe from non-terminating string reads.
1011         */
1012        memset(tsk->comm, 0, TASK_COMM_LEN);
1013        wmb();
1014        strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1015        task_unlock(tsk);
1016        perf_event_comm(tsk);
1017}
1018
1019int flush_old_exec(struct linux_binprm * bprm)
1020{
1021        int retval;
1022
1023        /*
1024         * Make sure we have a private signal table and that
1025         * we are unassociated from the previous thread group.
1026         */
1027        retval = de_thread(current);
1028        if (retval)
1029                goto out;
1030
1031        set_mm_exe_file(bprm->mm, bprm->file);
1032
1033        /*
1034         * Release all of the old mmap stuff
1035         */
1036        acct_arg_size(bprm, 0);
1037        retval = exec_mmap(bprm->mm);
1038        if (retval)
1039                goto out;
1040
1041        bprm->mm = NULL;                /* We're using it now */
1042
1043        current->flags &= ~(PF_RANDOMIZE | PF_KTHREAD);
1044        flush_thread();
1045        current->personality &= ~bprm->per_clear;
1046
1047        return 0;
1048
1049out:
1050        return retval;
1051}
1052EXPORT_SYMBOL(flush_old_exec);
1053
1054void setup_new_exec(struct linux_binprm * bprm)
1055{
1056        int i, ch;
1057        const char *name;
1058        char tcomm[sizeof(current->comm)];
1059
1060        arch_pick_mmap_layout(current->mm);
1061
1062        /* This is the point of no return */
1063        current->sas_ss_sp = current->sas_ss_size = 0;
1064
1065        if (current_euid() == current_uid() && current_egid() == current_gid())
1066                set_dumpable(current->mm, 1);
1067        else
1068                set_dumpable(current->mm, suid_dumpable);
1069
1070        name = bprm->filename;
1071
1072        /* Copies the binary name from after last slash */
1073        for (i=0; (ch = *(name++)) != '\0';) {
1074                if (ch == '/')
1075                        i = 0; /* overwrite what we wrote */
1076                else
1077                        if (i < (sizeof(tcomm) - 1))
1078                                tcomm[i++] = ch;
1079        }
1080        tcomm[i] = '\0';
1081        set_task_comm(current, tcomm);
1082
1083        /* Set the new mm task size. We have to do that late because it may
1084         * depend on TIF_32BIT which is only updated in flush_thread() on
1085         * some architectures like powerpc
1086         */
1087        current->mm->task_size = TASK_SIZE;
1088
1089        /* install the new credentials */
1090        if (bprm->cred->uid != current_euid() ||
1091            bprm->cred->gid != current_egid()) {
1092                current->pdeath_signal = 0;
1093        } else if (file_permission(bprm->file, MAY_READ) ||
1094                   bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1095                set_dumpable(current->mm, suid_dumpable);
1096        }
1097
1098        /*
1099         * Flush performance counters when crossing a
1100         * security domain:
1101         */
1102        if (!get_dumpable(current->mm))
1103                perf_event_exit_task(current);
1104
1105        /* An exec changes our domain. We are no longer part of the thread
1106           group */
1107
1108        current->self_exec_id++;
1109                        
1110        flush_signal_handlers(current, 0);
1111        flush_old_files(current->files);
1112}
1113EXPORT_SYMBOL(setup_new_exec);
1114
1115/*
1116 * Prepare credentials and lock ->cred_guard_mutex.
1117 * install_exec_creds() commits the new creds and drops the lock.
1118 * Or, if exec fails before, free_bprm() should release ->cred and
1119 * and unlock.
1120 */
1121int prepare_bprm_creds(struct linux_binprm *bprm)
1122{
1123        if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1124                return -ERESTARTNOINTR;
1125
1126        bprm->cred = prepare_exec_creds();
1127        if (likely(bprm->cred))
1128                return 0;
1129
1130        mutex_unlock(&current->signal->cred_guard_mutex);
1131        return -ENOMEM;
1132}
1133
1134void free_bprm(struct linux_binprm *bprm)
1135{
1136        free_arg_pages(bprm);
1137        if (bprm->cred) {
1138                mutex_unlock(&current->signal->cred_guard_mutex);
1139                abort_creds(bprm->cred);
1140        }
1141        kfree(bprm);
1142}
1143
1144/*
1145 * install the new credentials for this executable
1146 */
1147void install_exec_creds(struct linux_binprm *bprm)
1148{
1149        security_bprm_committing_creds(bprm);
1150
1151        commit_creds(bprm->cred);
1152        bprm->cred = NULL;
1153        /*
1154         * cred_guard_mutex must be held at least to this point to prevent
1155         * ptrace_attach() from altering our determination of the task's
1156         * credentials; any time after this it may be unlocked.
1157         */
1158        security_bprm_committed_creds(bprm);
1159        mutex_unlock(&current->signal->cred_guard_mutex);
1160}
1161EXPORT_SYMBOL(install_exec_creds);
1162
1163/*
1164 * determine how safe it is to execute the proposed program
1165 * - the caller must hold ->cred_guard_mutex to protect against
1166 *   PTRACE_ATTACH
1167 */
1168int check_unsafe_exec(struct linux_binprm *bprm)
1169{
1170        struct task_struct *p = current, *t;
1171        unsigned n_fs;
1172        int res = 0;
1173
1174        bprm->unsafe = tracehook_unsafe_exec(p);
1175
1176        n_fs = 1;
1177        spin_lock(&p->fs->lock);
1178        rcu_read_lock();
1179        for (t = next_thread(p); t != p; t = next_thread(t)) {
1180                if (t->fs == p->fs)
1181                        n_fs++;
1182        }
1183        rcu_read_unlock();
1184
1185        if (p->fs->users > n_fs) {
1186                bprm->unsafe |= LSM_UNSAFE_SHARE;
1187        } else {
1188                res = -EAGAIN;
1189                if (!p->fs->in_exec) {
1190                        p->fs->in_exec = 1;
1191                        res = 1;
1192                }
1193        }
1194        spin_unlock(&p->fs->lock);
1195
1196        return res;
1197}
1198
1199/* 
1200 * Fill the binprm structure from the inode. 
1201 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1202 *
1203 * This may be called multiple times for binary chains (scripts for example).
1204 */
1205int prepare_binprm(struct linux_binprm *bprm)
1206{
1207        umode_t mode;
1208        struct inode * inode = bprm->file->f_path.dentry->d_inode;
1209        int retval;
1210
1211        mode = inode->i_mode;
1212        if (bprm->file->f_op == NULL)
1213                return -EACCES;
1214
1215        /* clear any previous set[ug]id data from a previous binary */
1216        bprm->cred->euid = current_euid();
1217        bprm->cred->egid = current_egid();
1218
1219        if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1220                /* Set-uid? */
1221                if (mode & S_ISUID) {
1222                        bprm->per_clear |= PER_CLEAR_ON_SETID;
1223                        bprm->cred->euid = inode->i_uid;
1224                }
1225
1226                /* Set-gid? */
1227                /*
1228                 * If setgid is set but no group execute bit then this
1229                 * is a candidate for mandatory locking, not a setgid
1230                 * executable.
1231                 */
1232                if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1233                        bprm->per_clear |= PER_CLEAR_ON_SETID;
1234                        bprm->cred->egid = inode->i_gid;
1235                }
1236        }
1237
1238        /* fill in binprm security blob */
1239        retval = security_bprm_set_creds(bprm);
1240        if (retval)
1241                return retval;
1242        bprm->cred_prepared = 1;
1243
1244        memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1245        return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1246}
1247
1248EXPORT_SYMBOL(prepare_binprm);
1249
1250/*
1251 * Arguments are '\0' separated strings found at the location bprm->p
1252 * points to; chop off the first by relocating brpm->p to right after
1253 * the first '\0' encountered.
1254 */
1255int remove_arg_zero(struct linux_binprm *bprm)
1256{
1257        int ret = 0;
1258        unsigned long offset;
1259        char *kaddr;
1260        struct page *page;
1261
1262        if (!bprm->argc)
1263                return 0;
1264
1265        do {
1266                offset = bprm->p & ~PAGE_MASK;
1267                page = get_arg_page(bprm, bprm->p, 0);
1268                if (!page) {
1269                        ret = -EFAULT;
1270                        goto out;
1271                }
1272                kaddr = kmap_atomic(page, KM_USER0);
1273
1274                for (; offset < PAGE_SIZE && kaddr[offset];
1275                                offset++, bprm->p++)
1276                        ;
1277
1278                kunmap_atomic(kaddr, KM_USER0);
1279                put_arg_page(page);
1280
1281                if (offset == PAGE_SIZE)
1282                        free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1283        } while (offset == PAGE_SIZE);
1284
1285        bprm->p++;
1286        bprm->argc--;
1287        ret = 0;
1288
1289out:
1290        return ret;
1291}
1292EXPORT_SYMBOL(remove_arg_zero);
1293
1294/*
1295 * cycle the list of binary formats handler, until one recognizes the image
1296 */
1297int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1298{
1299        unsigned int depth = bprm->recursion_depth;
1300        int try,retval;
1301        struct linux_binfmt *fmt;
1302
1303        retval = security_bprm_check(bprm);
1304        if (retval)
1305                return retval;
1306
1307        /* kernel module loader fixup */
1308        /* so we don't try to load run modprobe in kernel space. */
1309        set_fs(USER_DS);
1310
1311        retval = audit_bprm(bprm);
1312        if (retval)
1313                return retval;
1314
1315        retval = -ENOENT;
1316        for (try=0; try<2; try++) {
1317                read_lock(&binfmt_lock);
1318                list_for_each_entry(fmt, &formats, lh) {
1319                        int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1320                        if (!fn)
1321                                continue;
1322                        if (!try_module_get(fmt->module))
1323                                continue;
1324                        read_unlock(&binfmt_lock);
1325                        retval = fn(bprm, regs);
1326                        /*
1327                         * Restore the depth counter to its starting value
1328                         * in this call, so we don't have to rely on every
1329                         * load_binary function to restore it on return.
1330                         */
1331                        bprm->recursion_depth = depth;
1332                        if (retval >= 0) {
1333                                if (depth == 0)
1334                                        tracehook_report_exec(fmt, bprm, regs);
1335                                put_binfmt(fmt);
1336                                allow_write_access(bprm->file);
1337                                if (bprm->file)
1338                                        fput(bprm->file);
1339                                bprm->file = NULL;
1340                                current->did_exec = 1;
1341                                proc_exec_connector(current);
1342                                return retval;
1343                        }
1344                        read_lock(&binfmt_lock);
1345                        put_binfmt(fmt);
1346                        if (retval != -ENOEXEC || bprm->mm == NULL)
1347                                break;
1348                        if (!bprm->file) {
1349                                read_unlock(&binfmt_lock);
1350                                return retval;
1351                        }
1352                }
1353                read_unlock(&binfmt_lock);
1354                if (retval != -ENOEXEC || bprm->mm == NULL) {
1355                        break;
1356#ifdef CONFIG_MODULES
1357                } else {
1358#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1359                        if (printable(bprm->buf[0]) &&
1360                            printable(bprm->buf[1]) &&
1361                            printable(bprm->buf[2]) &&
1362                            printable(bprm->buf[3]))
1363                                break; /* -ENOEXEC */
1364                        request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1365#endif
1366                }
1367        }
1368        return retval;
1369}
1370
1371EXPORT_SYMBOL(search_binary_handler);
1372
1373/*
1374 * sys_execve() executes a new program.
1375 */
1376int do_execve(const char * filename,
1377        const char __user *const __user *argv,
1378        const char __user *const __user *envp,
1379        struct pt_regs * regs)
1380{
1381        struct linux_binprm *bprm;
1382        struct file *file;
1383        struct files_struct *displaced;
1384        bool clear_in_exec;
1385        int retval;
1386
1387        retval = unshare_files(&displaced);
1388        if (retval)
1389                goto out_ret;
1390
1391        retval = -ENOMEM;
1392        bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1393        if (!bprm)
1394                goto out_files;
1395
1396        retval = prepare_bprm_creds(bprm);
1397        if (retval)
1398                goto out_free;
1399
1400        retval = check_unsafe_exec(bprm);
1401        if (retval < 0)
1402                goto out_free;
1403        clear_in_exec = retval;
1404        current->in_execve = 1;
1405
1406        file = open_exec(filename);
1407        retval = PTR_ERR(file);
1408        if (IS_ERR(file))
1409                goto out_unmark;
1410
1411        sched_exec();
1412
1413        bprm->file = file;
1414        bprm->filename = filename;
1415        bprm->interp = filename;
1416
1417        retval = bprm_mm_init(bprm);
1418        if (retval)
1419                goto out_file;
1420
1421        bprm->argc = count(argv, MAX_ARG_STRINGS);
1422        if ((retval = bprm->argc) < 0)
1423                goto out;
1424
1425        bprm->envc = count(envp, MAX_ARG_STRINGS);
1426        if ((retval = bprm->envc) < 0)
1427                goto out;
1428
1429        retval = prepare_binprm(bprm);
1430        if (retval < 0)
1431                goto out;
1432
1433        retval = copy_strings_kernel(1, &bprm->filename, bprm);
1434        if (retval < 0)
1435                goto out;
1436
1437        bprm->exec = bprm->p;
1438        retval = copy_strings(bprm->envc, envp, bprm);
1439        if (retval < 0)
1440                goto out;
1441
1442        retval = copy_strings(bprm->argc, argv, bprm);
1443        if (retval < 0)
1444                goto out;
1445
1446        retval = search_binary_handler(bprm,regs);
1447        if (retval < 0)
1448                goto out;
1449
1450        /* execve succeeded */
1451        current->fs->in_exec = 0;
1452        current->in_execve = 0;
1453        acct_update_integrals(current);
1454        free_bprm(bprm);
1455        if (displaced)
1456                put_files_struct(displaced);
1457        return retval;
1458
1459out:
1460        if (bprm->mm) {
1461                acct_arg_size(bprm, 0);
1462                mmput(bprm->mm);
1463        }
1464
1465out_file:
1466        if (bprm->file) {
1467                allow_write_access(bprm->file);
1468                fput(bprm->file);
1469        }
1470
1471out_unmark:
1472        if (clear_in_exec)
1473                current->fs->in_exec = 0;
1474        current->in_execve = 0;
1475
1476out_free:
1477        free_bprm(bprm);
1478
1479out_files:
1480        if (displaced)
1481                reset_files_struct(displaced);
1482out_ret:
1483        return retval;
1484}
1485
1486void set_binfmt(struct linux_binfmt *new)
1487{
1488        struct mm_struct *mm = current->mm;
1489
1490        if (mm->binfmt)
1491                module_put(mm->binfmt->module);
1492
1493        mm->binfmt = new;
1494        if (new)
1495                __module_get(new->module);
1496}
1497
1498EXPORT_SYMBOL(set_binfmt);
1499
1500static int expand_corename(struct core_name *cn)
1501{
1502        char *old_corename = cn->corename;
1503
1504        cn->size = CORENAME_MAX_SIZE * atomic_inc_return(&call_count);
1505        cn->corename = krealloc(old_corename, cn->size, GFP_KERNEL);
1506
1507        if (!cn->corename) {
1508                kfree(old_corename);
1509                return -ENOMEM;
1510        }
1511
1512        return 0;
1513}
1514
1515static int cn_printf(struct core_name *cn, const char *fmt, ...)
1516{
1517        char *cur;
1518        int need;
1519        int ret;
1520        va_list arg;
1521
1522        va_start(arg, fmt);
1523        need = vsnprintf(NULL, 0, fmt, arg);
1524        va_end(arg);
1525
1526        if (likely(need < cn->size - cn->used - 1))
1527                goto out_printf;
1528
1529        ret = expand_corename(cn);
1530        if (ret)
1531                goto expand_fail;
1532
1533out_printf:
1534        cur = cn->corename + cn->used;
1535        va_start(arg, fmt);
1536        vsnprintf(cur, need + 1, fmt, arg);
1537        va_end(arg);
1538        cn->used += need;
1539        return 0;
1540
1541expand_fail:
1542        return ret;
1543}
1544
1545/* format_corename will inspect the pattern parameter, and output a
1546 * name into corename, which must have space for at least
1547 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1548 */
1549static int format_corename(struct core_name *cn, long signr)
1550{
1551        const struct cred *cred = current_cred();
1552        const char *pat_ptr = core_pattern;
1553        int ispipe = (*pat_ptr == '|');
1554        int pid_in_pattern = 0;
1555        int err = 0;
1556
1557        cn->size = CORENAME_MAX_SIZE * atomic_read(&call_count);
1558        cn->corename = kmalloc(cn->size, GFP_KERNEL);
1559        cn->used = 0;
1560
1561        if (!cn->corename)
1562                return -ENOMEM;
1563
1564        /* Repeat as long as we have more pattern to process and more output
1565           space */
1566        while (*pat_ptr) {
1567                if (*pat_ptr != '%') {
1568                        if (*pat_ptr == 0)
1569                                goto out;
1570                        err = cn_printf(cn, "%c", *pat_ptr++);
1571                } else {
1572                        switch (*++pat_ptr) {
1573                        /* single % at the end, drop that */
1574                        case 0:
1575                                goto out;
1576                        /* Double percent, output one percent */
1577                        case '%':
1578                                err = cn_printf(cn, "%c", '%');
1579                                break;
1580                        /* pid */
1581                        case 'p':
1582                                pid_in_pattern = 1;
1583                                err = cn_printf(cn, "%d",
1584                                              task_tgid_vnr(current));
1585                                break;
1586                        /* uid */
1587                        case 'u':
1588                                err = cn_printf(cn, "%d", cred->uid);
1589                                break;
1590                        /* gid */
1591                        case 'g':
1592                                err = cn_printf(cn, "%d", cred->gid);
1593                                break;
1594                        /* signal that caused the coredump */
1595                        case 's':
1596                                err = cn_printf(cn, "%ld", signr);
1597                                break;
1598                        /* UNIX time of coredump */
1599                        case 't': {
1600                                struct timeval tv;
1601                                do_gettimeofday(&tv);
1602                                err = cn_printf(cn, "%lu", tv.tv_sec);
1603                                break;
1604                        }
1605                        /* hostname */
1606                        case 'h':
1607                                down_read(&uts_sem);
1608                                err = cn_printf(cn, "%s",
1609                                              utsname()->nodename);
1610                                up_read(&uts_sem);
1611                                break;
1612                        /* executable */
1613                        case 'e':
1614                                err = cn_printf(cn, "%s", current->comm);
1615                                break;
1616                        /* core limit size */
1617                        case 'c':
1618                                err = cn_printf(cn, "%lu",
1619                                              rlimit(RLIMIT_CORE));
1620                                break;
1621                        default:
1622                                break;
1623                        }
1624                        ++pat_ptr;
1625                }
1626
1627                if (err)
1628                        return err;
1629        }
1630
1631        /* Backward compatibility with core_uses_pid:
1632         *
1633         * If core_pattern does not include a %p (as is the default)
1634         * and core_uses_pid is set, then .%pid will be appended to
1635         * the filename. Do not do this for piped commands. */
1636        if (!ispipe && !pid_in_pattern && core_uses_pid) {
1637                err = cn_printf(cn, ".%d", task_tgid_vnr(current));
1638                if (err)
1639                        return err;
1640        }
1641out:
1642        return ispipe;
1643}
1644
1645static int zap_process(struct task_struct *start, int exit_code)
1646{
1647        struct task_struct *t;
1648        int nr = 0;
1649
1650        start->signal->flags = SIGNAL_GROUP_EXIT;
1651        start->signal->group_exit_code = exit_code;
1652        start->signal->group_stop_count = 0;
1653
1654        t = start;
1655        do {
1656                if (t != current && t->mm) {
1657                        sigaddset(&t->pending.signal, SIGKILL);
1658                        signal_wake_up(t, 1);
1659                        nr++;
1660                }
1661        } while_each_thread(start, t);
1662
1663        return nr;
1664}
1665
1666static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1667                                struct core_state *core_state, int exit_code)
1668{
1669        struct task_struct *g, *p;
1670        unsigned long flags;
1671        int nr = -EAGAIN;
1672
1673        spin_lock_irq(&tsk->sighand->siglock);
1674        if (!signal_group_exit(tsk->signal)) {
1675                mm->core_state = core_state;
1676                nr = zap_process(tsk, exit_code);
1677        }
1678        spin_unlock_irq(&tsk->sighand->siglock);
1679        if (unlikely(nr < 0))
1680                return nr;
1681
1682        if (atomic_read(&mm->mm_users) == nr + 1)
1683                goto done;
1684        /*
1685         * We should find and kill all tasks which use this mm, and we should
1686         * count them correctly into ->nr_threads. We don't take tasklist
1687         * lock, but this is safe wrt:
1688         *
1689         * fork:
1690         *      None of sub-threads can fork after zap_process(leader). All
1691         *      processes which were created before this point should be
1692         *      visible to zap_threads() because copy_process() adds the new
1693         *      process to the tail of init_task.tasks list, and lock/unlock
1694         *      of ->siglock provides a memory barrier.
1695         *
1696         * do_exit:
1697         *      The caller holds mm->mmap_sem. This means that the task which
1698         *      uses this mm can't pass exit_mm(), so it can't exit or clear
1699         *      its ->mm.
1700         *
1701         * de_thread:
1702         *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1703         *      we must see either old or new leader, this does not matter.
1704         *      However, it can change p->sighand, so lock_task_sighand(p)
1705         *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1706         *      it can't fail.
1707         *
1708         *      Note also that "g" can be the old leader with ->mm == NULL
1709         *      and already unhashed and thus removed from ->thread_group.
1710         *      This is OK, __unhash_process()->list_del_rcu() does not
1711         *      clear the ->next pointer, we will find the new leader via
1712         *      next_thread().
1713         */
1714        rcu_read_lock();
1715        for_each_process(g) {
1716                if (g == tsk->group_leader)
1717                        continue;
1718                if (g->flags & PF_KTHREAD)
1719                        continue;
1720                p = g;
1721                do {
1722                        if (p->mm) {
1723                                if (unlikely(p->mm == mm)) {
1724                                        lock_task_sighand(p, &flags);
1725                                        nr += zap_process(p, exit_code);
1726                                        unlock_task_sighand(p, &flags);
1727                                }
1728                                break;
1729                        }
1730                } while_each_thread(g, p);
1731        }
1732        rcu_read_unlock();
1733done:
1734        atomic_set(&core_state->nr_threads, nr);
1735        return nr;
1736}
1737
1738static int coredump_wait(int exit_code, struct core_state *core_state)
1739{
1740        struct task_struct *tsk = current;
1741        struct mm_struct *mm = tsk->mm;
1742        struct completion *vfork_done;
1743        int core_waiters = -EBUSY;
1744
1745        init_completion(&core_state->startup);
1746        core_state->dumper.task = tsk;
1747        core_state->dumper.next = NULL;
1748
1749        down_write(&mm->mmap_sem);
1750        if (!mm->core_state)
1751                core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1752        up_write(&mm->mmap_sem);
1753
1754        if (unlikely(core_waiters < 0))
1755                goto fail;
1756
1757        /*
1758         * Make sure nobody is waiting for us to release the VM,
1759         * otherwise we can deadlock when we wait on each other
1760         */
1761        vfork_done = tsk->vfork_done;
1762        if (vfork_done) {
1763                tsk->vfork_done = NULL;
1764                complete(vfork_done);
1765        }
1766
1767        if (core_waiters)
1768                wait_for_completion(&core_state->startup);
1769fail:
1770        return core_waiters;
1771}
1772
1773static void coredump_finish(struct mm_struct *mm)
1774{
1775        struct core_thread *curr, *next;
1776        struct task_struct *task;
1777
1778        next = mm->core_state->dumper.next;
1779        while ((curr = next) != NULL) {
1780                next = curr->next;
1781                task = curr->task;
1782                /*
1783                 * see exit_mm(), curr->task must not see
1784                 * ->task == NULL before we read ->next.
1785                 */
1786                smp_mb();
1787                curr->task = NULL;
1788                wake_up_process(task);
1789        }
1790
1791        mm->core_state = NULL;
1792}
1793
1794/*
1795 * set_dumpable converts traditional three-value dumpable to two flags and
1796 * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1797 * these bits are not changed atomically.  So get_dumpable can observe the
1798 * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1799 * return either old dumpable or new one by paying attention to the order of
1800 * modifying the bits.
1801 *
1802 * dumpable |   mm->flags (binary)
1803 * old  new | initial interim  final
1804 * ---------+-----------------------
1805 *  0    1  |   00      01      01
1806 *  0    2  |   00      10(*)   11
1807 *  1    0  |   01      00      00
1808 *  1    2  |   01      11      11
1809 *  2    0  |   11      10(*)   00
1810 *  2    1  |   11      11      01
1811 *
1812 * (*) get_dumpable regards interim value of 10 as 11.
1813 */
1814void set_dumpable(struct mm_struct *mm, int value)
1815{
1816        switch (value) {
1817        case 0:
1818                clear_bit(MMF_DUMPABLE, &mm->flags);
1819                smp_wmb();
1820                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1821                break;
1822        case 1:
1823                set_bit(MMF_DUMPABLE, &mm->flags);
1824                smp_wmb();
1825                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1826                break;
1827        case 2:
1828                set_bit(MMF_DUMP_SECURELY, &mm->flags);
1829                smp_wmb();
1830                set_bit(MMF_DUMPABLE, &mm->flags);
1831                break;
1832        }
1833}
1834
1835static int __get_dumpable(unsigned long mm_flags)
1836{
1837        int ret;
1838
1839        ret = mm_flags & MMF_DUMPABLE_MASK;
1840        return (ret >= 2) ? 2 : ret;
1841}
1842
1843int get_dumpable(struct mm_struct *mm)
1844{
1845        return __get_dumpable(mm->flags);
1846}
1847
1848static void wait_for_dump_helpers(struct file *file)
1849{
1850        struct pipe_inode_info *pipe;
1851
1852        pipe = file->f_path.dentry->d_inode->i_pipe;
1853
1854        pipe_lock(pipe);
1855        pipe->readers++;
1856        pipe->writers--;
1857
1858        while ((pipe->readers > 1) && (!signal_pending(current))) {
1859                wake_up_interruptible_sync(&pipe->wait);
1860                kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
1861                pipe_wait(pipe);
1862        }
1863
1864        pipe->readers--;
1865        pipe->writers++;
1866        pipe_unlock(pipe);
1867
1868}
1869
1870
1871/*
1872 * uhm_pipe_setup
1873 * helper function to customize the process used
1874 * to collect the core in userspace.  Specifically
1875 * it sets up a pipe and installs it as fd 0 (stdin)
1876 * for the process.  Returns 0 on success, or
1877 * PTR_ERR on failure.
1878 * Note that it also sets the core limit to 1.  This
1879 * is a special value that we use to trap recursive
1880 * core dumps
1881 */
1882static int umh_pipe_setup(struct subprocess_info *info)
1883{
1884        struct file *rp, *wp;
1885        struct fdtable *fdt;
1886        struct coredump_params *cp = (struct coredump_params *)info->data;
1887        struct files_struct *cf = current->files;
1888
1889        wp = create_write_pipe(0);
1890        if (IS_ERR(wp))
1891                return PTR_ERR(wp);
1892
1893        rp = create_read_pipe(wp, 0);
1894        if (IS_ERR(rp)) {
1895                free_write_pipe(wp);
1896                return PTR_ERR(rp);
1897        }
1898
1899        cp->file = wp;
1900
1901        sys_close(0);
1902        fd_install(0, rp);
1903        spin_lock(&cf->file_lock);
1904        fdt = files_fdtable(cf);
1905        FD_SET(0, fdt->open_fds);
1906        FD_CLR(0, fdt->close_on_exec);
1907        spin_unlock(&cf->file_lock);
1908
1909        /* and disallow core files too */
1910        current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
1911
1912        return 0;
1913}
1914
1915void do_coredump(long signr, int exit_code, struct pt_regs *regs)
1916{
1917        struct core_state core_state;
1918        struct core_name cn;
1919        struct mm_struct *mm = current->mm;
1920        struct linux_binfmt * binfmt;
1921        const struct cred *old_cred;
1922        struct cred *cred;
1923        int retval = 0;
1924        int flag = 0;
1925        int ispipe;
1926        static atomic_t core_dump_count = ATOMIC_INIT(0);
1927        struct coredump_params cprm = {
1928                .signr = signr,
1929                .regs = regs,
1930                .limit = rlimit(RLIMIT_CORE),
1931                /*
1932                 * We must use the same mm->flags while dumping core to avoid
1933                 * inconsistency of bit flags, since this flag is not protected
1934                 * by any locks.
1935                 */
1936                .mm_flags = mm->flags,
1937        };
1938
1939        audit_core_dumps(signr);
1940
1941        binfmt = mm->binfmt;
1942        if (!binfmt || !binfmt->core_dump)
1943                goto fail;
1944        if (!__get_dumpable(cprm.mm_flags))
1945                goto fail;
1946
1947        cred = prepare_creds();
1948        if (!cred)
1949                goto fail;
1950        /*
1951         *      We cannot trust fsuid as being the "true" uid of the
1952         *      process nor do we know its entire history. We only know it
1953         *      was tainted so we dump it as root in mode 2.
1954         */
1955        if (__get_dumpable(cprm.mm_flags) == 2) {
1956                /* Setuid core dump mode */
1957                flag = O_EXCL;          /* Stop rewrite attacks */
1958                cred->fsuid = 0;        /* Dump root private */
1959        }
1960
1961        retval = coredump_wait(exit_code, &core_state);
1962        if (retval < 0)
1963                goto fail_creds;
1964
1965        old_cred = override_creds(cred);
1966
1967        /*
1968         * Clear any false indication of pending signals that might
1969         * be seen by the filesystem code called to write the core file.
1970         */
1971        clear_thread_flag(TIF_SIGPENDING);
1972
1973        ispipe = format_corename(&cn, signr);
1974
1975        if (ispipe == -ENOMEM) {
1976                printk(KERN_WARNING "format_corename failed\n");
1977                printk(KERN_WARNING "Aborting core\n");
1978                goto fail_corename;
1979        }
1980
1981        if (ispipe) {
1982                int dump_count;
1983                char **helper_argv;
1984
1985                if (cprm.limit == 1) {
1986                        /*
1987                         * Normally core limits are irrelevant to pipes, since
1988                         * we're not writing to the file system, but we use
1989                         * cprm.limit of 1 here as a speacial value. Any
1990                         * non-1 limit gets set to RLIM_INFINITY below, but
1991                         * a limit of 0 skips the dump.  This is a consistent
1992                         * way to catch recursive crashes.  We can still crash
1993                         * if the core_pattern binary sets RLIM_CORE =  !1
1994                         * but it runs as root, and can do lots of stupid things
1995                         * Note that we use task_tgid_vnr here to grab the pid
1996                         * of the process group leader.  That way we get the
1997                         * right pid if a thread in a multi-threaded
1998                         * core_pattern process dies.
1999                         */
2000                        printk(KERN_WARNING
2001                                "Process %d(%s) has RLIMIT_CORE set to 1\n",
2002                                task_tgid_vnr(current), current->comm);
2003                        printk(KERN_WARNING "Aborting core\n");
2004                        goto fail_unlock;
2005                }
2006                cprm.limit = RLIM_INFINITY;
2007
2008                dump_count = atomic_inc_return(&core_dump_count);
2009                if (core_pipe_limit && (core_pipe_limit < dump_count)) {
2010                        printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
2011                               task_tgid_vnr(current), current->comm);
2012                        printk(KERN_WARNING "Skipping core dump\n");
2013                        goto fail_dropcount;
2014                }
2015
2016                helper_argv = argv_split(GFP_KERNEL, cn.corename+1, NULL);
2017                if (!helper_argv) {
2018                        printk(KERN_WARNING "%s failed to allocate memory\n",
2019                               __func__);
2020                        goto fail_dropcount;
2021                }
2022
2023                retval = call_usermodehelper_fns(helper_argv[0], helper_argv,
2024                                        NULL, UMH_WAIT_EXEC, umh_pipe_setup,
2025                                        NULL, &cprm);
2026                argv_free(helper_argv);
2027                if (retval) {
2028                        printk(KERN_INFO "Core dump to %s pipe failed\n",
2029                               cn.corename);
2030                        goto close_fail;
2031                }
2032        } else {
2033                struct inode *inode;
2034
2035                if (cprm.limit < binfmt->min_coredump)
2036                        goto fail_unlock;
2037
2038                cprm.file = filp_open(cn.corename,
2039                                 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
2040                                 0600);
2041                if (IS_ERR(cprm.file))
2042                        goto fail_unlock;
2043
2044                inode = cprm.file->f_path.dentry->d_inode;
2045                if (inode->i_nlink > 1)
2046                        goto close_fail;
2047                if (d_unhashed(cprm.file->f_path.dentry))
2048                        goto close_fail;
2049                /*
2050                 * AK: actually i see no reason to not allow this for named
2051                 * pipes etc, but keep the previous behaviour for now.
2052                 */
2053                if (!S_ISREG(inode->i_mode))
2054                        goto close_fail;
2055                /*
2056                 * Dont allow local users get cute and trick others to coredump
2057                 * into their pre-created files.
2058                 */
2059                if (inode->i_uid != current_fsuid())
2060                        goto close_fail;
2061                if (!cprm.file->f_op || !cprm.file->f_op->write)
2062                        goto close_fail;
2063                if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
2064                        goto close_fail;
2065        }
2066
2067        retval = binfmt->core_dump(&cprm);
2068        if (retval)
2069                current->signal->group_exit_code |= 0x80;
2070
2071        if (ispipe && core_pipe_limit)
2072                wait_for_dump_helpers(cprm.file);
2073close_fail:
2074        if (cprm.file)
2075                filp_close(cprm.file, NULL);
2076fail_dropcount:
2077        if (ispipe)
2078                atomic_dec(&core_dump_count);
2079fail_unlock:
2080        kfree(cn.corename);
2081fail_corename:
2082        coredump_finish(mm);
2083        revert_creds(old_cred);
2084fail_creds:
2085        put_cred(cred);
2086fail:
2087        return;
2088}
2089
2090/*
2091 * Core dumping helper functions.  These are the only things you should
2092 * do on a core-file: use only these functions to write out all the
2093 * necessary info.
2094 */
2095int dump_write(struct file *file, const void *addr, int nr)
2096{
2097        return access_ok(VERIFY_READ, addr, nr) && file->f_op->write(file, addr, nr, &file->f_pos) == nr;
2098}
2099EXPORT_SYMBOL(dump_write);
2100
2101int dump_seek(struct file *file, loff_t off)
2102{
2103        int ret = 1;
2104
2105        if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
2106                if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
2107                        return 0;
2108        } else {
2109                char *buf = (char *)get_zeroed_page(GFP_KERNEL);
2110
2111                if (!buf)
2112                        return 0;
2113                while (off > 0) {
2114                        unsigned long n = off;
2115
2116                        if (n > PAGE_SIZE)
2117                                n = PAGE_SIZE;
2118                        if (!dump_write(file, buf, n)) {
2119                                ret = 0;
2120                                break;
2121                        }
2122                        off -= n;
2123                }
2124                free_page((unsigned long)buf);
2125        }
2126        return ret;
2127}
2128EXPORT_SYMBOL(dump_seek);
2129
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