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/mount.h>
  46#include <linux/security.h>
  47#include <linux/syscalls.h>
  48#include <linux/tsacct_kern.h>
  49#include <linux/cn_proc.h>
  50#include <linux/audit.h>
  51#include <linux/tracehook.h>
  52#include <linux/kmod.h>
  53#include <linux/fsnotify.h>
  54#include <linux/fs_struct.h>
  55#include <linux/pipe_fs_i.h>
  56#include <linux/oom.h>
  57#include <linux/compat.h>
  58
  59#include <asm/uaccess.h>
  60#include <asm/mmu_context.h>
  61#include <asm/tlb.h>
  62
  63#include <trace/events/task.h>
  64#include "internal.h"
  65#include "coredump.h"
  66
  67#include <trace/events/sched.h>
  68
  69int suid_dumpable = 0;
  70
  71static LIST_HEAD(formats);
  72static DEFINE_RWLOCK(binfmt_lock);
  73
  74void __register_binfmt(struct linux_binfmt * fmt, int insert)
  75{
  76        BUG_ON(!fmt);
  77        write_lock(&binfmt_lock);
  78        insert ? list_add(&fmt->lh, &formats) :
  79                 list_add_tail(&fmt->lh, &formats);
  80        write_unlock(&binfmt_lock);
  81}
  82
  83EXPORT_SYMBOL(__register_binfmt);
  84
  85void unregister_binfmt(struct linux_binfmt * fmt)
  86{
  87        write_lock(&binfmt_lock);
  88        list_del(&fmt->lh);
  89        write_unlock(&binfmt_lock);
  90}
  91
  92EXPORT_SYMBOL(unregister_binfmt);
  93
  94static inline void put_binfmt(struct linux_binfmt * fmt)
  95{
  96        module_put(fmt->module);
  97}
  98
  99/*
 100 * Note that a shared library must be both readable and executable due to
 101 * security reasons.
 102 *
 103 * Also note that we take the address to load from from the file itself.
 104 */
 105SYSCALL_DEFINE1(uselib, const char __user *, library)
 106{
 107        struct file *file;
 108        struct filename *tmp = getname(library);
 109        int error = PTR_ERR(tmp);
 110        static const struct open_flags uselib_flags = {
 111                .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 112                .acc_mode = MAY_READ | MAY_EXEC | MAY_OPEN,
 113                .intent = LOOKUP_OPEN,
 114                .lookup_flags = LOOKUP_FOLLOW,
 115        };
 116
 117        if (IS_ERR(tmp))
 118                goto out;
 119
 120        file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
 121        putname(tmp);
 122        error = PTR_ERR(file);
 123        if (IS_ERR(file))
 124                goto out;
 125
 126        error = -EINVAL;
 127        if (!S_ISREG(file_inode(file)->i_mode))
 128                goto exit;
 129
 130        error = -EACCES;
 131        if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 132                goto exit;
 133
 134        fsnotify_open(file);
 135
 136        error = -ENOEXEC;
 137        if(file->f_op) {
 138                struct linux_binfmt * fmt;
 139
 140                read_lock(&binfmt_lock);
 141                list_for_each_entry(fmt, &formats, lh) {
 142                        if (!fmt->load_shlib)
 143                                continue;
 144                        if (!try_module_get(fmt->module))
 145                                continue;
 146                        read_unlock(&binfmt_lock);
 147                        error = fmt->load_shlib(file);
 148                        read_lock(&binfmt_lock);
 149                        put_binfmt(fmt);
 150                        if (error != -ENOEXEC)
 151                                break;
 152                }
 153                read_unlock(&binfmt_lock);
 154        }
 155exit:
 156        fput(file);
 157out:
 158        return error;
 159}
 160
 161#ifdef CONFIG_MMU
 162/*
 163 * The nascent bprm->mm is not visible until exec_mmap() but it can
 164 * use a lot of memory, account these pages in current->mm temporary
 165 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 166 * change the counter back via acct_arg_size(0).
 167 */
 168static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 169{
 170        struct mm_struct *mm = current->mm;
 171        long diff = (long)(pages - bprm->vma_pages);
 172
 173        if (!mm || !diff)
 174                return;
 175
 176        bprm->vma_pages = pages;
 177        add_mm_counter(mm, MM_ANONPAGES, diff);
 178}
 179
 180static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 181                int write)
 182{
 183        struct page *page;
 184        int ret;
 185
 186#ifdef CONFIG_STACK_GROWSUP
 187        if (write) {
 188                ret = expand_downwards(bprm->vma, pos);
 189                if (ret < 0)
 190                        return NULL;
 191        }
 192#endif
 193        ret = get_user_pages(current, bprm->mm, pos,
 194                        1, write, 1, &page, NULL);
 195        if (ret <= 0)
 196                return NULL;
 197
 198        if (write) {
 199                unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 200                struct rlimit *rlim;
 201
 202                acct_arg_size(bprm, size / PAGE_SIZE);
 203
 204                /*
 205                 * We've historically supported up to 32 pages (ARG_MAX)
 206                 * of argument strings even with small stacks
 207                 */
 208                if (size <= ARG_MAX)
 209                        return page;
 210
 211                /*
 212                 * Limit to 1/4-th the stack size for the argv+env strings.
 213                 * This ensures that:
 214                 *  - the remaining binfmt code will not run out of stack space,
 215                 *  - the program will have a reasonable amount of stack left
 216                 *    to work from.
 217                 */
 218                rlim = current->signal->rlim;
 219                if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 220                        put_page(page);
 221                        return NULL;
 222                }
 223        }
 224
 225        return page;
 226}
 227
 228static void put_arg_page(struct page *page)
 229{
 230        put_page(page);
 231}
 232
 233static void free_arg_page(struct linux_binprm *bprm, int i)
 234{
 235}
 236
 237static void free_arg_pages(struct linux_binprm *bprm)
 238{
 239}
 240
 241static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 242                struct page *page)
 243{
 244        flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 245}
 246
 247static int __bprm_mm_init(struct linux_binprm *bprm)
 248{
 249        int err;
 250        struct vm_area_struct *vma = NULL;
 251        struct mm_struct *mm = bprm->mm;
 252
 253        bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 254        if (!vma)
 255                return -ENOMEM;
 256
 257        down_write(&mm->mmap_sem);
 258        vma->vm_mm = mm;
 259
 260        /*
 261         * Place the stack at the largest stack address the architecture
 262         * supports. Later, we'll move this to an appropriate place. We don't
 263         * use STACK_TOP because that can depend on attributes which aren't
 264         * configured yet.
 265         */
 266        BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 267        vma->vm_end = STACK_TOP_MAX;
 268        vma->vm_start = vma->vm_end - PAGE_SIZE;
 269        vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 270        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 271        INIT_LIST_HEAD(&vma->anon_vma_chain);
 272
 273        err = insert_vm_struct(mm, vma);
 274        if (err)
 275                goto err;
 276
 277        mm->stack_vm = mm->total_vm = 1;
 278        up_write(&mm->mmap_sem);
 279        bprm->p = vma->vm_end - sizeof(void *);
 280        return 0;
 281err:
 282        up_write(&mm->mmap_sem);
 283        bprm->vma = NULL;
 284        kmem_cache_free(vm_area_cachep, vma);
 285        return err;
 286}
 287
 288static bool valid_arg_len(struct linux_binprm *bprm, long len)
 289{
 290        return len <= MAX_ARG_STRLEN;
 291}
 292
 293#else
 294
 295static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 296{
 297}
 298
 299static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 300                int write)
 301{
 302        struct page *page;
 303
 304        page = bprm->page[pos / PAGE_SIZE];
 305        if (!page && write) {
 306                page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 307                if (!page)
 308                        return NULL;
 309                bprm->page[pos / PAGE_SIZE] = page;
 310        }
 311
 312        return page;
 313}
 314
 315static void put_arg_page(struct page *page)
 316{
 317}
 318
 319static void free_arg_page(struct linux_binprm *bprm, int i)
 320{
 321        if (bprm->page[i]) {
 322                __free_page(bprm->page[i]);
 323                bprm->page[i] = NULL;
 324        }
 325}
 326
 327static void free_arg_pages(struct linux_binprm *bprm)
 328{
 329        int i;
 330
 331        for (i = 0; i < MAX_ARG_PAGES; i++)
 332                free_arg_page(bprm, i);
 333}
 334
 335static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 336                struct page *page)
 337{
 338}
 339
 340static int __bprm_mm_init(struct linux_binprm *bprm)
 341{
 342        bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 343        return 0;
 344}
 345
 346static bool valid_arg_len(struct linux_binprm *bprm, long len)
 347{
 348        return len <= bprm->p;
 349}
 350
 351#endif /* CONFIG_MMU */
 352
 353/*
 354 * Create a new mm_struct and populate it with a temporary stack
 355 * vm_area_struct.  We don't have enough context at this point to set the stack
 356 * flags, permissions, and offset, so we use temporary values.  We'll update
 357 * them later in setup_arg_pages().
 358 */
 359static int bprm_mm_init(struct linux_binprm *bprm)
 360{
 361        int err;
 362        struct mm_struct *mm = NULL;
 363
 364        bprm->mm = mm = mm_alloc();
 365        err = -ENOMEM;
 366        if (!mm)
 367                goto err;
 368
 369        err = init_new_context(current, mm);
 370        if (err)
 371                goto err;
 372
 373        err = __bprm_mm_init(bprm);
 374        if (err)
 375                goto err;
 376
 377        return 0;
 378
 379err:
 380        if (mm) {
 381                bprm->mm = NULL;
 382                mmdrop(mm);
 383        }
 384
 385        return err;
 386}
 387
 388struct user_arg_ptr {
 389#ifdef CONFIG_COMPAT
 390        bool is_compat;
 391#endif
 392        union {
 393                const char __user *const __user *native;
 394#ifdef CONFIG_COMPAT
 395                const compat_uptr_t __user *compat;
 396#endif
 397        } ptr;
 398};
 399
 400static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 401{
 402        const char __user *native;
 403
 404#ifdef CONFIG_COMPAT
 405        if (unlikely(argv.is_compat)) {
 406                compat_uptr_t compat;
 407
 408                if (get_user(compat, argv.ptr.compat + nr))
 409                        return ERR_PTR(-EFAULT);
 410
 411                return compat_ptr(compat);
 412        }
 413#endif
 414
 415        if (get_user(native, argv.ptr.native + nr))
 416                return ERR_PTR(-EFAULT);
 417
 418        return native;
 419}
 420
 421/*
 422 * count() counts the number of strings in array ARGV.
 423 */
 424static int count(struct user_arg_ptr argv, int max)
 425{
 426        int i = 0;
 427
 428        if (argv.ptr.native != NULL) {
 429                for (;;) {
 430                        const char __user *p = get_user_arg_ptr(argv, i);
 431
 432                        if (!p)
 433                                break;
 434
 435                        if (IS_ERR(p))
 436                                return -EFAULT;
 437
 438                        if (i >= max)
 439                                return -E2BIG;
 440                        ++i;
 441
 442                        if (fatal_signal_pending(current))
 443                                return -ERESTARTNOHAND;
 444                        cond_resched();
 445                }
 446        }
 447        return i;
 448}
 449
 450/*
 451 * 'copy_strings()' copies argument/environment strings from the old
 452 * processes's memory to the new process's stack.  The call to get_user_pages()
 453 * ensures the destination page is created and not swapped out.
 454 */
 455static int copy_strings(int argc, struct user_arg_ptr argv,
 456                        struct linux_binprm *bprm)
 457{
 458        struct page *kmapped_page = NULL;
 459        char *kaddr = NULL;
 460        unsigned long kpos = 0;
 461        int ret;
 462
 463        while (argc-- > 0) {
 464                const char __user *str;
 465                int len;
 466                unsigned long pos;
 467
 468                ret = -EFAULT;
 469                str = get_user_arg_ptr(argv, argc);
 470                if (IS_ERR(str))
 471                        goto out;
 472
 473                len = strnlen_user(str, MAX_ARG_STRLEN);
 474                if (!len)
 475                        goto out;
 476
 477                ret = -E2BIG;
 478                if (!valid_arg_len(bprm, len))
 479                        goto out;
 480
 481                /* We're going to work our way backwords. */
 482                pos = bprm->p;
 483                str += len;
 484                bprm->p -= len;
 485
 486                while (len > 0) {
 487                        int offset, bytes_to_copy;
 488
 489                        if (fatal_signal_pending(current)) {
 490                                ret = -ERESTARTNOHAND;
 491                                goto out;
 492                        }
 493                        cond_resched();
 494
 495                        offset = pos % PAGE_SIZE;
 496                        if (offset == 0)
 497                                offset = PAGE_SIZE;
 498
 499                        bytes_to_copy = offset;
 500                        if (bytes_to_copy > len)
 501                                bytes_to_copy = len;
 502
 503                        offset -= bytes_to_copy;
 504                        pos -= bytes_to_copy;
 505                        str -= bytes_to_copy;
 506                        len -= bytes_to_copy;
 507
 508                        if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 509                                struct page *page;
 510
 511                                page = get_arg_page(bprm, pos, 1);
 512                                if (!page) {
 513                                        ret = -E2BIG;
 514                                        goto out;
 515                                }
 516
 517                                if (kmapped_page) {
 518                                        flush_kernel_dcache_page(kmapped_page);
 519                                        kunmap(kmapped_page);
 520                                        put_arg_page(kmapped_page);
 521                                }
 522                                kmapped_page = page;
 523                                kaddr = kmap(kmapped_page);
 524                                kpos = pos & PAGE_MASK;
 525                                flush_arg_page(bprm, kpos, kmapped_page);
 526                        }
 527                        if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 528                                ret = -EFAULT;
 529                                goto out;
 530                        }
 531                }
 532        }
 533        ret = 0;
 534out:
 535        if (kmapped_page) {
 536                flush_kernel_dcache_page(kmapped_page);
 537                kunmap(kmapped_page);
 538                put_arg_page(kmapped_page);
 539        }
 540        return ret;
 541}
 542
 543/*
 544 * Like copy_strings, but get argv and its values from kernel memory.
 545 */
 546int copy_strings_kernel(int argc, const char *const *__argv,
 547                        struct linux_binprm *bprm)
 548{
 549        int r;
 550        mm_segment_t oldfs = get_fs();
 551        struct user_arg_ptr argv = {
 552                .ptr.native = (const char __user *const  __user *)__argv,
 553        };
 554
 555        set_fs(KERNEL_DS);
 556        r = copy_strings(argc, argv, bprm);
 557        set_fs(oldfs);
 558
 559        return r;
 560}
 561EXPORT_SYMBOL(copy_strings_kernel);
 562
 563#ifdef CONFIG_MMU
 564
 565/*
 566 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 567 * the binfmt code determines where the new stack should reside, we shift it to
 568 * its final location.  The process proceeds as follows:
 569 *
 570 * 1) Use shift to calculate the new vma endpoints.
 571 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 572 *    arguments passed to subsequent functions are consistent.
 573 * 3) Move vma's page tables to the new range.
 574 * 4) Free up any cleared pgd range.
 575 * 5) Shrink the vma to cover only the new range.
 576 */
 577static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 578{
 579        struct mm_struct *mm = vma->vm_mm;
 580        unsigned long old_start = vma->vm_start;
 581        unsigned long old_end = vma->vm_end;
 582        unsigned long length = old_end - old_start;
 583        unsigned long new_start = old_start - shift;
 584        unsigned long new_end = old_end - shift;
 585        struct mmu_gather tlb;
 586
 587        BUG_ON(new_start > new_end);
 588
 589        /*
 590         * ensure there are no vmas between where we want to go
 591         * and where we are
 592         */
 593        if (vma != find_vma(mm, new_start))
 594                return -EFAULT;
 595
 596        /*
 597         * cover the whole range: [new_start, old_end)
 598         */
 599        if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 600                return -ENOMEM;
 601
 602        /*
 603         * move the page tables downwards, on failure we rely on
 604         * process cleanup to remove whatever mess we made.
 605         */
 606        if (length != move_page_tables(vma, old_start,
 607                                       vma, new_start, length, false))
 608                return -ENOMEM;
 609
 610        lru_add_drain();
 611        tlb_gather_mmu(&tlb, mm, old_start, old_end);
 612        if (new_end > old_start) {
 613                /*
 614                 * when the old and new regions overlap clear from new_end.
 615                 */
 616                free_pgd_range(&tlb, new_end, old_end, new_end,
 617                        vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 618        } else {
 619                /*
 620                 * otherwise, clean from old_start; this is done to not touch
 621                 * the address space in [new_end, old_start) some architectures
 622                 * have constraints on va-space that make this illegal (IA64) -
 623                 * for the others its just a little faster.
 624                 */
 625                free_pgd_range(&tlb, old_start, old_end, new_end,
 626                        vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 627        }
 628        tlb_finish_mmu(&tlb, old_start, old_end);
 629
 630        /*
 631         * Shrink the vma to just the new range.  Always succeeds.
 632         */
 633        vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 634
 635        return 0;
 636}
 637
 638/*
 639 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 640 * the stack is optionally relocated, and some extra space is added.
 641 */
 642int setup_arg_pages(struct linux_binprm *bprm,
 643                    unsigned long stack_top,
 644                    int executable_stack)
 645{
 646        unsigned long ret;
 647        unsigned long stack_shift;
 648        struct mm_struct *mm = current->mm;
 649        struct vm_area_struct *vma = bprm->vma;
 650        struct vm_area_struct *prev = NULL;
 651        unsigned long vm_flags;
 652        unsigned long stack_base;
 653        unsigned long stack_size;
 654        unsigned long stack_expand;
 655        unsigned long rlim_stack;
 656
 657#ifdef CONFIG_STACK_GROWSUP
 658        /* Limit stack size to 1GB */
 659        stack_base = rlimit_max(RLIMIT_STACK);
 660        if (stack_base > (1 << 30))
 661                stack_base = 1 << 30;
 662
 663        /* Make sure we didn't let the argument array grow too large. */
 664        if (vma->vm_end - vma->vm_start > stack_base)
 665                return -ENOMEM;
 666
 667        stack_base = PAGE_ALIGN(stack_top - stack_base);
 668
 669        stack_shift = vma->vm_start - stack_base;
 670        mm->arg_start = bprm->p - stack_shift;
 671        bprm->p = vma->vm_end - stack_shift;
 672#else
 673        stack_top = arch_align_stack(stack_top);
 674        stack_top = PAGE_ALIGN(stack_top);
 675
 676        if (unlikely(stack_top < mmap_min_addr) ||
 677            unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 678                return -ENOMEM;
 679
 680        stack_shift = vma->vm_end - stack_top;
 681
 682        bprm->p -= stack_shift;
 683        mm->arg_start = bprm->p;
 684#endif
 685
 686        if (bprm->loader)
 687                bprm->loader -= stack_shift;
 688        bprm->exec -= stack_shift;
 689
 690        down_write(&mm->mmap_sem);
 691        vm_flags = VM_STACK_FLAGS;
 692
 693        /*
 694         * Adjust stack execute permissions; explicitly enable for
 695         * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 696         * (arch default) otherwise.
 697         */
 698        if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 699                vm_flags |= VM_EXEC;
 700        else if (executable_stack == EXSTACK_DISABLE_X)
 701                vm_flags &= ~VM_EXEC;
 702        vm_flags |= mm->def_flags;
 703        vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 704
 705        ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 706                        vm_flags);
 707        if (ret)
 708                goto out_unlock;
 709        BUG_ON(prev != vma);
 710
 711        /* Move stack pages down in memory. */
 712        if (stack_shift) {
 713                ret = shift_arg_pages(vma, stack_shift);
 714                if (ret)
 715                        goto out_unlock;
 716        }
 717
 718        /* mprotect_fixup is overkill to remove the temporary stack flags */
 719        vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 720
 721        stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 722        stack_size = vma->vm_end - vma->vm_start;
 723        /*
 724         * Align this down to a page boundary as expand_stack
 725         * will align it up.
 726         */
 727        rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 728#ifdef CONFIG_STACK_GROWSUP
 729        if (stack_size + stack_expand > rlim_stack)
 730                stack_base = vma->vm_start + rlim_stack;
 731        else
 732                stack_base = vma->vm_end + stack_expand;
 733#else
 734        if (stack_size + stack_expand > rlim_stack)
 735                stack_base = vma->vm_end - rlim_stack;
 736        else
 737                stack_base = vma->vm_start - stack_expand;
 738#endif
 739        current->mm->start_stack = bprm->p;
 740        ret = expand_stack(vma, stack_base);
 741        if (ret)
 742                ret = -EFAULT;
 743
 744out_unlock:
 745        up_write(&mm->mmap_sem);
 746        return ret;
 747}
 748EXPORT_SYMBOL(setup_arg_pages);
 749
 750#endif /* CONFIG_MMU */
 751
 752struct file *open_exec(const char *name)
 753{
 754        struct file *file;
 755        int err;
 756        struct filename tmp = { .name = name };
 757        static const struct open_flags open_exec_flags = {
 758                .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 759                .acc_mode = MAY_EXEC | MAY_OPEN,
 760                .intent = LOOKUP_OPEN,
 761                .lookup_flags = LOOKUP_FOLLOW,
 762        };
 763
 764        file = do_filp_open(AT_FDCWD, &tmp, &open_exec_flags);
 765        if (IS_ERR(file))
 766                goto out;
 767
 768        err = -EACCES;
 769        if (!S_ISREG(file_inode(file)->i_mode))
 770                goto exit;
 771
 772        if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 773                goto exit;
 774
 775        fsnotify_open(file);
 776
 777        err = deny_write_access(file);
 778        if (err)
 779                goto exit;
 780
 781out:
 782        return file;
 783
 784exit:
 785        fput(file);
 786        return ERR_PTR(err);
 787}
 788EXPORT_SYMBOL(open_exec);
 789
 790int kernel_read(struct file *file, loff_t offset,
 791                char *addr, unsigned long count)
 792{
 793        mm_segment_t old_fs;
 794        loff_t pos = offset;
 795        int result;
 796
 797        old_fs = get_fs();
 798        set_fs(get_ds());
 799        /* The cast to a user pointer is valid due to the set_fs() */
 800        result = vfs_read(file, (void __user *)addr, count, &pos);
 801        set_fs(old_fs);
 802        return result;
 803}
 804
 805EXPORT_SYMBOL(kernel_read);
 806
 807ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 808{
 809        ssize_t res = file->f_op->read(file, (void __user *)addr, len, &pos);
 810        if (res > 0)
 811                flush_icache_range(addr, addr + len);
 812        return res;
 813}
 814EXPORT_SYMBOL(read_code);
 815
 816static int exec_mmap(struct mm_struct *mm)
 817{
 818        struct task_struct *tsk;
 819        struct mm_struct * old_mm, *active_mm;
 820
 821        /* Notify parent that we're no longer interested in the old VM */
 822        tsk = current;
 823        old_mm = current->mm;
 824        mm_release(tsk, old_mm);
 825
 826        if (old_mm) {
 827                sync_mm_rss(old_mm);
 828                /*
 829                 * Make sure that if there is a core dump in progress
 830                 * for the old mm, we get out and die instead of going
 831                 * through with the exec.  We must hold mmap_sem around
 832                 * checking core_state and changing tsk->mm.
 833                 */
 834                down_read(&old_mm->mmap_sem);
 835                if (unlikely(old_mm->core_state)) {
 836                        up_read(&old_mm->mmap_sem);
 837                        return -EINTR;
 838                }
 839        }
 840        task_lock(tsk);
 841        active_mm = tsk->active_mm;
 842        tsk->mm = mm;
 843        tsk->active_mm = mm;
 844        activate_mm(active_mm, mm);
 845        task_unlock(tsk);
 846        arch_pick_mmap_layout(mm);
 847        if (old_mm) {
 848                up_read(&old_mm->mmap_sem);
 849                BUG_ON(active_mm != old_mm);
 850                setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
 851                mm_update_next_owner(old_mm);
 852                mmput(old_mm);
 853                return 0;
 854        }
 855        mmdrop(active_mm);
 856        return 0;
 857}
 858
 859/*
 860 * This function makes sure the current process has its own signal table,
 861 * so that flush_signal_handlers can later reset the handlers without
 862 * disturbing other processes.  (Other processes might share the signal
 863 * table via the CLONE_SIGHAND option to clone().)
 864 */
 865static int de_thread(struct task_struct *tsk)
 866{
 867        struct signal_struct *sig = tsk->signal;
 868        struct sighand_struct *oldsighand = tsk->sighand;
 869        spinlock_t *lock = &oldsighand->siglock;
 870
 871        if (thread_group_empty(tsk))
 872                goto no_thread_group;
 873
 874        /*
 875         * Kill all other threads in the thread group.
 876         */
 877        spin_lock_irq(lock);
 878        if (signal_group_exit(sig)) {
 879                /*
 880                 * Another group action in progress, just
 881                 * return so that the signal is processed.
 882                 */
 883                spin_unlock_irq(lock);
 884                return -EAGAIN;
 885        }
 886
 887        sig->group_exit_task = tsk;
 888        sig->notify_count = zap_other_threads(tsk);
 889        if (!thread_group_leader(tsk))
 890                sig->notify_count--;
 891
 892        while (sig->notify_count) {
 893                __set_current_state(TASK_KILLABLE);
 894                spin_unlock_irq(lock);
 895                schedule();
 896                if (unlikely(__fatal_signal_pending(tsk)))
 897                        goto killed;
 898                spin_lock_irq(lock);
 899        }
 900        spin_unlock_irq(lock);
 901
 902        /*
 903         * At this point all other threads have exited, all we have to
 904         * do is to wait for the thread group leader to become inactive,
 905         * and to assume its PID:
 906         */
 907        if (!thread_group_leader(tsk)) {
 908                struct task_struct *leader = tsk->group_leader;
 909
 910                sig->notify_count = -1; /* for exit_notify() */
 911                for (;;) {
 912                        threadgroup_change_begin(tsk);
 913                        write_lock_irq(&tasklist_lock);
 914                        if (likely(leader->exit_state))
 915                                break;
 916                        __set_current_state(TASK_KILLABLE);
 917                        write_unlock_irq(&tasklist_lock);
 918                        threadgroup_change_end(tsk);
 919                        schedule();
 920                        if (unlikely(__fatal_signal_pending(tsk)))
 921                                goto killed;
 922                }
 923
 924                /*
 925                 * The only record we have of the real-time age of a
 926                 * process, regardless of execs it's done, is start_time.
 927                 * All the past CPU time is accumulated in signal_struct
 928                 * from sister threads now dead.  But in this non-leader
 929                 * exec, nothing survives from the original leader thread,
 930                 * whose birth marks the true age of this process now.
 931                 * When we take on its identity by switching to its PID, we
 932                 * also take its birthdate (always earlier than our own).
 933                 */
 934                tsk->start_time = leader->start_time;
 935                tsk->real_start_time = leader->real_start_time;
 936
 937                BUG_ON(!same_thread_group(leader, tsk));
 938                BUG_ON(has_group_leader_pid(tsk));
 939                /*
 940                 * An exec() starts a new thread group with the
 941                 * TGID of the previous thread group. Rehash the
 942                 * two threads with a switched PID, and release
 943                 * the former thread group leader:
 944                 */
 945
 946                /* Become a process group leader with the old leader's pid.
 947                 * The old leader becomes a thread of the this thread group.
 948                 * Note: The old leader also uses this pid until release_task
 949                 *       is called.  Odd but simple and correct.
 950                 */
 951                tsk->pid = leader->pid;
 952                change_pid(tsk, PIDTYPE_PID, task_pid(leader));
 953                transfer_pid(leader, tsk, PIDTYPE_PGID);
 954                transfer_pid(leader, tsk, PIDTYPE_SID);
 955
 956                list_replace_rcu(&leader->tasks, &tsk->tasks);
 957                list_replace_init(&leader->sibling, &tsk->sibling);
 958
 959                tsk->group_leader = tsk;
 960                leader->group_leader = tsk;
 961
 962                tsk->exit_signal = SIGCHLD;
 963                leader->exit_signal = -1;
 964
 965                BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 966                leader->exit_state = EXIT_DEAD;
 967
 968                /*
 969                 * We are going to release_task()->ptrace_unlink() silently,
 970                 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
 971                 * the tracer wont't block again waiting for this thread.
 972                 */
 973                if (unlikely(leader->ptrace))
 974                        __wake_up_parent(leader, leader->parent);
 975                write_unlock_irq(&tasklist_lock);
 976                threadgroup_change_end(tsk);
 977
 978                release_task(leader);
 979        }
 980
 981        sig->group_exit_task = NULL;
 982        sig->notify_count = 0;
 983
 984no_thread_group:
 985        /* we have changed execution domain */
 986        tsk->exit_signal = SIGCHLD;
 987
 988        exit_itimers(sig);
 989        flush_itimer_signals();
 990
 991        if (atomic_read(&oldsighand->count) != 1) {
 992                struct sighand_struct *newsighand;
 993                /*
 994                 * This ->sighand is shared with the CLONE_SIGHAND
 995                 * but not CLONE_THREAD task, switch to the new one.
 996                 */
 997                newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 998                if (!newsighand)
 999                        return -ENOMEM;
1000
1001                atomic_set(&newsighand->count, 1);
1002                memcpy(newsighand->action, oldsighand->action,
1003                       sizeof(newsighand->action));
1004
1005                write_lock_irq(&tasklist_lock);
1006                spin_lock(&oldsighand->siglock);
1007                rcu_assign_pointer(tsk->sighand, newsighand);
1008                spin_unlock(&oldsighand->siglock);
1009                write_unlock_irq(&tasklist_lock);
1010
1011                __cleanup_sighand(oldsighand);
1012        }
1013
1014        BUG_ON(!thread_group_leader(tsk));
1015        return 0;
1016
1017killed:
1018        /* protects against exit_notify() and __exit_signal() */
1019        read_lock(&tasklist_lock);
1020        sig->group_exit_task = NULL;
1021        sig->notify_count = 0;
1022        read_unlock(&tasklist_lock);
1023        return -EAGAIN;
1024}
1025
1026char *get_task_comm(char *buf, struct task_struct *tsk)
1027{
1028        /* buf must be at least sizeof(tsk->comm) in size */
1029        task_lock(tsk);
1030        strncpy(buf, tsk->comm, sizeof(tsk->comm));
1031        task_unlock(tsk);
1032        return buf;
1033}
1034EXPORT_SYMBOL_GPL(get_task_comm);
1035
1036/*
1037 * These functions flushes out all traces of the currently running executable
1038 * so that a new one can be started
1039 */
1040
1041void set_task_comm(struct task_struct *tsk, char *buf)
1042{
1043        task_lock(tsk);
1044        trace_task_rename(tsk, buf);
1045        strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1046        task_unlock(tsk);
1047        perf_event_comm(tsk);
1048}
1049
1050static void filename_to_taskname(char *tcomm, const char *fn, unsigned int len)
1051{
1052        int i, ch;
1053
1054        /* Copies the binary name from after last slash */
1055        for (i = 0; (ch = *(fn++)) != '\0';) {
1056                if (ch == '/')
1057                        i = 0; /* overwrite what we wrote */
1058                else
1059                        if (i < len - 1)
1060                                tcomm[i++] = ch;
1061        }
1062        tcomm[i] = '\0';
1063}
1064
1065int flush_old_exec(struct linux_binprm * bprm)
1066{
1067        int retval;
1068
1069        /*
1070         * Make sure we have a private signal table and that
1071         * we are unassociated from the previous thread group.
1072         */
1073        retval = de_thread(current);
1074        if (retval)
1075                goto out;
1076
1077        set_mm_exe_file(bprm->mm, bprm->file);
1078
1079        filename_to_taskname(bprm->tcomm, bprm->filename, sizeof(bprm->tcomm));
1080        /*
1081         * Release all of the old mmap stuff
1082         */
1083        acct_arg_size(bprm, 0);
1084        retval = exec_mmap(bprm->mm);
1085        if (retval)
1086                goto out;
1087
1088        bprm->mm = NULL;                /* We're using it now */
1089
1090        set_fs(USER_DS);
1091        current->flags &=
1092                ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | PF_NOFREEZE);
1093        flush_thread();
1094        current->personality &= ~bprm->per_clear;
1095
1096        return 0;
1097
1098out:
1099        return retval;
1100}
1101EXPORT_SYMBOL(flush_old_exec);
1102
1103void would_dump(struct linux_binprm *bprm, struct file *file)
1104{
1105        if (inode_permission(file_inode(file), MAY_READ) < 0)
1106                bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1107}
1108EXPORT_SYMBOL(would_dump);
1109
1110void setup_new_exec(struct linux_binprm * bprm)
1111{
1112        arch_pick_mmap_layout(current->mm);
1113
1114        /* This is the point of no return */
1115        current->sas_ss_sp = current->sas_ss_size = 0;
1116
1117        if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1118                set_dumpable(current->mm, SUID_DUMP_USER);
1119        else
1120                set_dumpable(current->mm, suid_dumpable);
1121
1122        set_task_comm(current, bprm->tcomm);
1123
1124        /* Set the new mm task size. We have to do that late because it may
1125         * depend on TIF_32BIT which is only updated in flush_thread() on
1126         * some architectures like powerpc
1127         */
1128        current->mm->task_size = TASK_SIZE;
1129
1130        /* install the new credentials */
1131        if (!uid_eq(bprm->cred->uid, current_euid()) ||
1132            !gid_eq(bprm->cred->gid, current_egid())) {
1133                current->pdeath_signal = 0;
1134        } else {
1135                would_dump(bprm, bprm->file);
1136                if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1137                        set_dumpable(current->mm, suid_dumpable);
1138        }
1139
1140        /* An exec changes our domain. We are no longer part of the thread
1141           group */
1142
1143        current->self_exec_id++;
1144                        
1145        flush_signal_handlers(current, 0);
1146        do_close_on_exec(current->files);
1147}
1148EXPORT_SYMBOL(setup_new_exec);
1149
1150/*
1151 * Prepare credentials and lock ->cred_guard_mutex.
1152 * install_exec_creds() commits the new creds and drops the lock.
1153 * Or, if exec fails before, free_bprm() should release ->cred and
1154 * and unlock.
1155 */
1156int prepare_bprm_creds(struct linux_binprm *bprm)
1157{
1158        if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1159                return -ERESTARTNOINTR;
1160
1161        bprm->cred = prepare_exec_creds();
1162        if (likely(bprm->cred))
1163                return 0;
1164
1165        mutex_unlock(&current->signal->cred_guard_mutex);
1166        return -ENOMEM;
1167}
1168
1169void free_bprm(struct linux_binprm *bprm)
1170{
1171        free_arg_pages(bprm);
1172        if (bprm->cred) {
1173                mutex_unlock(&current->signal->cred_guard_mutex);
1174                abort_creds(bprm->cred);
1175        }
1176        /* If a binfmt changed the interp, free it. */
1177        if (bprm->interp != bprm->filename)
1178                kfree(bprm->interp);
1179        kfree(bprm);
1180}
1181
1182int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1183{
1184        /* If a binfmt changed the interp, free it first. */
1185        if (bprm->interp != bprm->filename)
1186                kfree(bprm->interp);
1187        bprm->interp = kstrdup(interp, GFP_KERNEL);
1188        if (!bprm->interp)
1189                return -ENOMEM;
1190        return 0;
1191}
1192EXPORT_SYMBOL(bprm_change_interp);
1193
1194/*
1195 * install the new credentials for this executable
1196 */
1197void install_exec_creds(struct linux_binprm *bprm)
1198{
1199        security_bprm_committing_creds(bprm);
1200
1201        commit_creds(bprm->cred);
1202        bprm->cred = NULL;
1203
1204        /*
1205         * Disable monitoring for regular users
1206         * when executing setuid binaries. Must
1207         * wait until new credentials are committed
1208         * by commit_creds() above
1209         */
1210        if (get_dumpable(current->mm) != SUID_DUMP_USER)
1211                perf_event_exit_task(current);
1212        /*
1213         * cred_guard_mutex must be held at least to this point to prevent
1214         * ptrace_attach() from altering our determination of the task's
1215         * credentials; any time after this it may be unlocked.
1216         */
1217        security_bprm_committed_creds(bprm);
1218        mutex_unlock(&current->signal->cred_guard_mutex);
1219}
1220EXPORT_SYMBOL(install_exec_creds);
1221
1222/*
1223 * determine how safe it is to execute the proposed program
1224 * - the caller must hold ->cred_guard_mutex to protect against
1225 *   PTRACE_ATTACH
1226 */
1227static int check_unsafe_exec(struct linux_binprm *bprm)
1228{
1229        struct task_struct *p = current, *t;
1230        unsigned n_fs;
1231        int res = 0;
1232
1233        if (p->ptrace) {
1234                if (p->ptrace & PT_PTRACE_CAP)
1235                        bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1236                else
1237                        bprm->unsafe |= LSM_UNSAFE_PTRACE;
1238        }
1239
1240        /*
1241         * This isn't strictly necessary, but it makes it harder for LSMs to
1242         * mess up.
1243         */
1244        if (current->no_new_privs)
1245                bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1246
1247        n_fs = 1;
1248        spin_lock(&p->fs->lock);
1249        rcu_read_lock();
1250        for (t = next_thread(p); t != p; t = next_thread(t)) {
1251                if (t->fs == p->fs)
1252                        n_fs++;
1253        }
1254        rcu_read_unlock();
1255
1256        if (p->fs->users > n_fs) {
1257                bprm->unsafe |= LSM_UNSAFE_SHARE;
1258        } else {
1259                res = -EAGAIN;
1260                if (!p->fs->in_exec) {
1261                        p->fs->in_exec = 1;
1262                        res = 1;
1263                }
1264        }
1265        spin_unlock(&p->fs->lock);
1266
1267        return res;
1268}
1269
1270/* 
1271 * Fill the binprm structure from the inode. 
1272 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1273 *
1274 * This may be called multiple times for binary chains (scripts for example).
1275 */
1276int prepare_binprm(struct linux_binprm *bprm)
1277{
1278        umode_t mode;
1279        struct inode * inode = file_inode(bprm->file);
1280        int retval;
1281
1282        mode = inode->i_mode;
1283        if (bprm->file->f_op == NULL)
1284                return -EACCES;
1285
1286        /* clear any previous set[ug]id data from a previous binary */
1287        bprm->cred->euid = current_euid();
1288        bprm->cred->egid = current_egid();
1289
1290        if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) &&
1291            !current->no_new_privs &&
1292            kuid_has_mapping(bprm->cred->user_ns, inode->i_uid) &&
1293            kgid_has_mapping(bprm->cred->user_ns, inode->i_gid)) {
1294                /* Set-uid? */
1295                if (mode & S_ISUID) {
1296                        bprm->per_clear |= PER_CLEAR_ON_SETID;
1297                        bprm->cred->euid = inode->i_uid;
1298                }
1299
1300                /* Set-gid? */
1301                /*
1302                 * If setgid is set but no group execute bit then this
1303                 * is a candidate for mandatory locking, not a setgid
1304                 * executable.
1305                 */
1306                if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1307                        bprm->per_clear |= PER_CLEAR_ON_SETID;
1308                        bprm->cred->egid = inode->i_gid;
1309                }
1310        }
1311
1312        /* fill in binprm security blob */
1313        retval = security_bprm_set_creds(bprm);
1314        if (retval)
1315                return retval;
1316        bprm->cred_prepared = 1;
1317
1318        memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1319        return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1320}
1321
1322EXPORT_SYMBOL(prepare_binprm);
1323
1324/*
1325 * Arguments are '\0' separated strings found at the location bprm->p
1326 * points to; chop off the first by relocating brpm->p to right after
1327 * the first '\0' encountered.
1328 */
1329int remove_arg_zero(struct linux_binprm *bprm)
1330{
1331        int ret = 0;
1332        unsigned long offset;
1333        char *kaddr;
1334        struct page *page;
1335
1336        if (!bprm->argc)
1337                return 0;
1338
1339        do {
1340                offset = bprm->p & ~PAGE_MASK;
1341                page = get_arg_page(bprm, bprm->p, 0);
1342                if (!page) {
1343                        ret = -EFAULT;
1344                        goto out;
1345                }
1346                kaddr = kmap_atomic(page);
1347
1348                for (; offset < PAGE_SIZE && kaddr[offset];
1349                                offset++, bprm->p++)
1350                        ;
1351
1352                kunmap_atomic(kaddr);
1353                put_arg_page(page);
1354
1355                if (offset == PAGE_SIZE)
1356                        free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1357        } while (offset == PAGE_SIZE);
1358
1359        bprm->p++;
1360        bprm->argc--;
1361        ret = 0;
1362
1363out:
1364        return ret;
1365}
1366EXPORT_SYMBOL(remove_arg_zero);
1367
1368/*
1369 * cycle the list of binary formats handler, until one recognizes the image
1370 */
1371int search_binary_handler(struct linux_binprm *bprm)
1372{
1373        unsigned int depth = bprm->recursion_depth;
1374        int try,retval;
1375        struct linux_binfmt *fmt;
1376        pid_t old_pid, old_vpid;
1377
1378        /* This allows 4 levels of binfmt rewrites before failing hard. */
1379        if (depth > 5)
1380                return -ELOOP;
1381
1382        retval = security_bprm_check(bprm);
1383        if (retval)
1384                return retval;
1385
1386        retval = audit_bprm(bprm);
1387        if (retval)
1388                return retval;
1389
1390        /* Need to fetch pid before load_binary changes it */
1391        old_pid = current->pid;
1392        rcu_read_lock();
1393        old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1394        rcu_read_unlock();
1395
1396        retval = -ENOENT;
1397        for (try=0; try<2; try++) {
1398                read_lock(&binfmt_lock);
1399                list_for_each_entry(fmt, &formats, lh) {
1400                        int (*fn)(struct linux_binprm *) = fmt->load_binary;
1401                        if (!fn)
1402                                continue;
1403                        if (!try_module_get(fmt->module))
1404                                continue;
1405                        read_unlock(&binfmt_lock);
1406                        bprm->recursion_depth = depth + 1;
1407                        retval = fn(bprm);
1408                        bprm->recursion_depth = depth;
1409                        if (retval >= 0) {
1410                                if (depth == 0) {
1411                                        trace_sched_process_exec(current, old_pid, bprm);
1412                                        ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1413                                }
1414                                put_binfmt(fmt);
1415                                allow_write_access(bprm->file);
1416                                if (bprm->file)
1417                                        fput(bprm->file);
1418                                bprm->file = NULL;
1419                                current->did_exec = 1;
1420                                proc_exec_connector(current);
1421                                return retval;
1422                        }
1423                        read_lock(&binfmt_lock);
1424                        put_binfmt(fmt);
1425                        if (retval != -ENOEXEC || bprm->mm == NULL)
1426                                break;
1427                        if (!bprm->file) {
1428                                read_unlock(&binfmt_lock);
1429                                return retval;
1430                        }
1431                }
1432                read_unlock(&binfmt_lock);
1433#ifdef CONFIG_MODULES
1434                if (retval != -ENOEXEC || bprm->mm == NULL) {
1435                        break;
1436                } else {
1437#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1438                        if (printable(bprm->buf[0]) &&
1439                            printable(bprm->buf[1]) &&
1440                            printable(bprm->buf[2]) &&
1441                            printable(bprm->buf[3]))
1442                                break; /* -ENOEXEC */
1443                        if (try)
1444                                break; /* -ENOEXEC */
1445                        request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1446                }
1447#else
1448                break;
1449#endif
1450        }
1451        return retval;
1452}
1453
1454EXPORT_SYMBOL(search_binary_handler);
1455
1456/*
1457 * sys_execve() executes a new program.
1458 */
1459static int do_execve_common(const char *filename,
1460                                struct user_arg_ptr argv,
1461                                struct user_arg_ptr envp)
1462{
1463        struct linux_binprm *bprm;
1464        struct file *file;
1465        struct files_struct *displaced;
1466        bool clear_in_exec;
1467        int retval;
1468
1469        /*
1470         * We move the actual failure in case of RLIMIT_NPROC excess from
1471         * set*uid() to execve() because too many poorly written programs
1472         * don't check setuid() return code.  Here we additionally recheck
1473         * whether NPROC limit is still exceeded.
1474         */
1475        if ((current->flags & PF_NPROC_EXCEEDED) &&
1476            atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1477                retval = -EAGAIN;
1478                goto out_ret;
1479        }
1480
1481        /* We're below the limit (still or again), so we don't want to make
1482         * further execve() calls fail. */
1483        current->flags &= ~PF_NPROC_EXCEEDED;
1484
1485        retval = unshare_files(&displaced);
1486        if (retval)
1487                goto out_ret;
1488
1489        retval = -ENOMEM;
1490        bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1491        if (!bprm)
1492                goto out_files;
1493
1494        retval = prepare_bprm_creds(bprm);
1495        if (retval)
1496                goto out_free;
1497
1498        retval = check_unsafe_exec(bprm);
1499        if (retval < 0)
1500                goto out_free;
1501        clear_in_exec = retval;
1502        current->in_execve = 1;
1503
1504        file = open_exec(filename);
1505        retval = PTR_ERR(file);
1506        if (IS_ERR(file))
1507                goto out_unmark;
1508
1509        sched_exec();
1510
1511        bprm->file = file;
1512        bprm->filename = filename;
1513        bprm->interp = filename;
1514
1515        retval = bprm_mm_init(bprm);
1516        if (retval)
1517                goto out_file;
1518
1519        bprm->argc = count(argv, MAX_ARG_STRINGS);
1520        if ((retval = bprm->argc) < 0)
1521                goto out;
1522
1523        bprm->envc = count(envp, MAX_ARG_STRINGS);
1524        if ((retval = bprm->envc) < 0)
1525                goto out;
1526
1527        retval = prepare_binprm(bprm);
1528        if (retval < 0)
1529                goto out;
1530
1531        retval = copy_strings_kernel(1, &bprm->filename, bprm);
1532        if (retval < 0)
1533                goto out;
1534
1535        bprm->exec = bprm->p;
1536        retval = copy_strings(bprm->envc, envp, bprm);
1537        if (retval < 0)
1538                goto out;
1539
1540        retval = copy_strings(bprm->argc, argv, bprm);
1541        if (retval < 0)
1542                goto out;
1543
1544        retval = search_binary_handler(bprm);
1545        if (retval < 0)
1546                goto out;
1547
1548        /* execve succeeded */
1549        current->fs->in_exec = 0;
1550        current->in_execve = 0;
1551        acct_update_integrals(current);
1552        free_bprm(bprm);
1553        if (displaced)
1554                put_files_struct(displaced);
1555        return retval;
1556
1557out:
1558        if (bprm->mm) {
1559                acct_arg_size(bprm, 0);
1560                mmput(bprm->mm);
1561        }
1562
1563out_file:
1564        if (bprm->file) {
1565                allow_write_access(bprm->file);
1566                fput(bprm->file);
1567        }
1568
1569out_unmark:
1570        if (clear_in_exec)
1571                current->fs->in_exec = 0;
1572        current->in_execve = 0;
1573
1574out_free:
1575        free_bprm(bprm);
1576
1577out_files:
1578        if (displaced)
1579                reset_files_struct(displaced);
1580out_ret:
1581        return retval;
1582}
1583
1584int do_execve(const char *filename,
1585        const char __user *const __user *__argv,
1586        const char __user *const __user *__envp)
1587{
1588        struct user_arg_ptr argv = { .ptr.native = __argv };
1589        struct user_arg_ptr envp = { .ptr.native = __envp };
1590        return do_execve_common(filename, argv, envp);
1591}
1592
1593#ifdef CONFIG_COMPAT
1594static int compat_do_execve(const char *filename,
1595        const compat_uptr_t __user *__argv,
1596        const compat_uptr_t __user *__envp)
1597{
1598        struct user_arg_ptr argv = {
1599                .is_compat = true,
1600                .ptr.compat = __argv,
1601        };
1602        struct user_arg_ptr envp = {
1603                .is_compat = true,
1604                .ptr.compat = __envp,
1605        };
1606        return do_execve_common(filename, argv, envp);
1607}
1608#endif
1609
1610void set_binfmt(struct linux_binfmt *new)
1611{
1612        struct mm_struct *mm = current->mm;
1613
1614        if (mm->binfmt)
1615                module_put(mm->binfmt->module);
1616
1617        mm->binfmt = new;
1618        if (new)
1619                __module_get(new->module);
1620}
1621
1622EXPORT_SYMBOL(set_binfmt);
1623
1624/*
1625 * set_dumpable converts traditional three-value dumpable to two flags and
1626 * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1627 * these bits are not changed atomically.  So get_dumpable can observe the
1628 * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1629 * return either old dumpable or new one by paying attention to the order of
1630 * modifying the bits.
1631 *
1632 * dumpable |   mm->flags (binary)
1633 * old  new | initial interim  final
1634 * ---------+-----------------------
1635 *  0    1  |   00      01      01
1636 *  0    2  |   00      10(*)   11
1637 *  1    0  |   01      00      00
1638 *  1    2  |   01      11      11
1639 *  2    0  |   11      10(*)   00
1640 *  2    1  |   11      11      01
1641 *
1642 * (*) get_dumpable regards interim value of 10 as 11.
1643 */
1644void set_dumpable(struct mm_struct *mm, int value)
1645{
1646        switch (value) {
1647        case SUID_DUMP_DISABLE:
1648                clear_bit(MMF_DUMPABLE, &mm->flags);
1649                smp_wmb();
1650                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1651                break;
1652        case SUID_DUMP_USER:
1653                set_bit(MMF_DUMPABLE, &mm->flags);
1654                smp_wmb();
1655                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1656                break;
1657        case SUID_DUMP_ROOT:
1658                set_bit(MMF_DUMP_SECURELY, &mm->flags);
1659                smp_wmb();
1660                set_bit(MMF_DUMPABLE, &mm->flags);
1661                break;
1662        }
1663}
1664
1665int __get_dumpable(unsigned long mm_flags)
1666{
1667        int ret;
1668
1669        ret = mm_flags & MMF_DUMPABLE_MASK;
1670        return (ret > SUID_DUMP_USER) ? SUID_DUMP_ROOT : ret;
1671}
1672
1673int get_dumpable(struct mm_struct *mm)
1674{
1675        return __get_dumpable(mm->flags);
1676}
1677
1678SYSCALL_DEFINE3(execve,
1679                const char __user *, filename,
1680                const char __user *const __user *, argv,
1681                const char __user *const __user *, envp)
1682{
1683        struct filename *path = getname(filename);
1684        int error = PTR_ERR(path);
1685        if (!IS_ERR(path)) {
1686                error = do_execve(path->name, argv, envp);
1687                putname(path);
1688        }
1689        return error;
1690}
1691#ifdef CONFIG_COMPAT
1692asmlinkage long compat_sys_execve(const char __user * filename,
1693        const compat_uptr_t __user * argv,
1694        const compat_uptr_t __user * envp)
1695{
1696        struct filename *path = getname(filename);
1697        int error = PTR_ERR(path);
1698        if (!IS_ERR(path)) {
1699                error = compat_do_execve(path->name, argv, envp);
1700                putname(path);
1701        }
1702        return error;
1703}
1704#endif
1705
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