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        };
 115
 116        if (IS_ERR(tmp))
 117                goto out;
 118
 119        file = do_filp_open(AT_FDCWD, tmp, &uselib_flags, LOOKUP_FOLLOW);
 120        putname(tmp);
 121        error = PTR_ERR(file);
 122        if (IS_ERR(file))
 123                goto out;
 124
 125        error = -EINVAL;
 126        if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 127                goto exit;
 128
 129        error = -EACCES;
 130        if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 131                goto exit;
 132
 133        fsnotify_open(file);
 134
 135        error = -ENOEXEC;
 136        if(file->f_op) {
 137                struct linux_binfmt * fmt;
 138
 139                read_lock(&binfmt_lock);
 140                list_for_each_entry(fmt, &formats, lh) {
 141                        if (!fmt->load_shlib)
 142                                continue;
 143                        if (!try_module_get(fmt->module))
 144                                continue;
 145                        read_unlock(&binfmt_lock);
 146                        error = fmt->load_shlib(file);
 147                        read_lock(&binfmt_lock);
 148                        put_binfmt(fmt);
 149                        if (error != -ENOEXEC)
 150                                break;
 151                }
 152                read_unlock(&binfmt_lock);
 153        }
 154exit:
 155        fput(file);
 156out:
 157        return error;
 158}
 159
 160#ifdef CONFIG_MMU
 161/*
 162 * The nascent bprm->mm is not visible until exec_mmap() but it can
 163 * use a lot of memory, account these pages in current->mm temporary
 164 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 165 * change the counter back via acct_arg_size(0).
 166 */
 167static void 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        add_mm_counter(mm, MM_ANONPAGES, diff);
 177}
 178
 179static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 180                int write)
 181{
 182        struct page *page;
 183        int ret;
 184
 185#ifdef CONFIG_STACK_GROWSUP
 186        if (write) {
 187                ret = expand_downwards(bprm->vma, pos);
 188                if (ret < 0)
 189                        return NULL;
 190        }
 191#endif
 192        ret = get_user_pages(current, bprm->mm, pos,
 193                        1, write, 1, &page, NULL);
 194        if (ret <= 0)
 195                return NULL;
 196
 197        if (write) {
 198                unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 199                struct rlimit *rlim;
 200
 201                acct_arg_size(bprm, size / PAGE_SIZE);
 202
 203                /*
 204                 * We've historically supported up to 32 pages (ARG_MAX)
 205                 * of argument strings even with small stacks
 206                 */
 207                if (size <= ARG_MAX)
 208                        return page;
 209
 210                /*
 211                 * Limit to 1/4-th the stack size for the argv+env strings.
 212                 * This ensures that:
 213                 *  - the remaining binfmt code will not run out of stack space,
 214                 *  - the program will have a reasonable amount of stack left
 215                 *    to work from.
 216                 */
 217                rlim = current->signal->rlim;
 218                if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 219                        put_page(page);
 220                        return NULL;
 221                }
 222        }
 223
 224        return page;
 225}
 226
 227static void put_arg_page(struct page *page)
 228{
 229        put_page(page);
 230}
 231
 232static void free_arg_page(struct linux_binprm *bprm, int i)
 233{
 234}
 235
 236static void free_arg_pages(struct linux_binprm *bprm)
 237{
 238}
 239
 240static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 241                struct page *page)
 242{
 243        flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 244}
 245
 246static int __bprm_mm_init(struct linux_binprm *bprm)
 247{
 248        int err;
 249        struct vm_area_struct *vma = NULL;
 250        struct mm_struct *mm = bprm->mm;
 251
 252        bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 253        if (!vma)
 254                return -ENOMEM;
 255
 256        down_write(&mm->mmap_sem);
 257        vma->vm_mm = mm;
 258
 259        /*
 260         * Place the stack at the largest stack address the architecture
 261         * supports. Later, we'll move this to an appropriate place. We don't
 262         * use STACK_TOP because that can depend on attributes which aren't
 263         * configured yet.
 264         */
 265        BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 266        vma->vm_end = STACK_TOP_MAX;
 267        vma->vm_start = vma->vm_end - PAGE_SIZE;
 268        vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 269        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 270        INIT_LIST_HEAD(&vma->anon_vma_chain);
 271
 272        err = insert_vm_struct(mm, vma);
 273        if (err)
 274                goto err;
 275
 276        mm->stack_vm = mm->total_vm = 1;
 277        up_write(&mm->mmap_sem);
 278        bprm->p = vma->vm_end - sizeof(void *);
 279        return 0;
 280err:
 281        up_write(&mm->mmap_sem);
 282        bprm->vma = NULL;
 283        kmem_cache_free(vm_area_cachep, vma);
 284        return err;
 285}
 286
 287static bool valid_arg_len(struct linux_binprm *bprm, long len)
 288{
 289        return len <= MAX_ARG_STRLEN;
 290}
 291
 292#else
 293
 294static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 295{
 296}
 297
 298static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 299                int write)
 300{
 301        struct page *page;
 302
 303        page = bprm->page[pos / PAGE_SIZE];
 304        if (!page && write) {
 305                page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 306                if (!page)
 307                        return NULL;
 308                bprm->page[pos / PAGE_SIZE] = page;
 309        }
 310
 311        return page;
 312}
 313
 314static void put_arg_page(struct page *page)
 315{
 316}
 317
 318static void free_arg_page(struct linux_binprm *bprm, int i)
 319{
 320        if (bprm->page[i]) {
 321                __free_page(bprm->page[i]);
 322                bprm->page[i] = NULL;
 323        }
 324}
 325
 326static void free_arg_pages(struct linux_binprm *bprm)
 327{
 328        int i;
 329
 330        for (i = 0; i < MAX_ARG_PAGES; i++)
 331                free_arg_page(bprm, i);
 332}
 333
 334static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 335                struct page *page)
 336{
 337}
 338
 339static int __bprm_mm_init(struct linux_binprm *bprm)
 340{
 341        bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 342        return 0;
 343}
 344
 345static bool valid_arg_len(struct linux_binprm *bprm, long len)
 346{
 347        return len <= bprm->p;
 348}
 349
 350#endif /* CONFIG_MMU */
 351
 352/*
 353 * Create a new mm_struct and populate it with a temporary stack
 354 * vm_area_struct.  We don't have enough context at this point to set the stack
 355 * flags, permissions, and offset, so we use temporary values.  We'll update
 356 * them later in setup_arg_pages().
 357 */
 358int bprm_mm_init(struct linux_binprm *bprm)
 359{
 360        int err;
 361        struct mm_struct *mm = NULL;
 362
 363        bprm->mm = mm = mm_alloc();
 364        err = -ENOMEM;
 365        if (!mm)
 366                goto err;
 367
 368        err = init_new_context(current, mm);
 369        if (err)
 370                goto err;
 371
 372        err = __bprm_mm_init(bprm);
 373        if (err)
 374                goto err;
 375
 376        return 0;
 377
 378err:
 379        if (mm) {
 380                bprm->mm = NULL;
 381                mmdrop(mm);
 382        }
 383
 384        return err;
 385}
 386
 387struct user_arg_ptr {
 388#ifdef CONFIG_COMPAT
 389        bool is_compat;
 390#endif
 391        union {
 392                const char __user *const __user *native;
 393#ifdef CONFIG_COMPAT
 394                const compat_uptr_t __user *compat;
 395#endif
 396        } ptr;
 397};
 398
 399static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 400{
 401        const char __user *native;
 402
 403#ifdef CONFIG_COMPAT
 404        if (unlikely(argv.is_compat)) {
 405                compat_uptr_t compat;
 406
 407                if (get_user(compat, argv.ptr.compat + nr))
 408                        return ERR_PTR(-EFAULT);
 409
 410                return compat_ptr(compat);
 411        }
 412#endif
 413
 414        if (get_user(native, argv.ptr.native + nr))
 415                return ERR_PTR(-EFAULT);
 416
 417        return native;
 418}
 419
 420/*
 421 * count() counts the number of strings in array ARGV.
 422 */
 423static int count(struct user_arg_ptr argv, int max)
 424{
 425        int i = 0;
 426
 427        if (argv.ptr.native != NULL) {
 428                for (;;) {
 429                        const char __user *p = get_user_arg_ptr(argv, i);
 430
 431                        if (!p)
 432                                break;
 433
 434                        if (IS_ERR(p))
 435                                return -EFAULT;
 436
 437                        if (i++ >= max)
 438                                return -E2BIG;
 439
 440                        if (fatal_signal_pending(current))
 441                                return -ERESTARTNOHAND;
 442                        cond_resched();
 443                }
 444        }
 445        return i;
 446}
 447
 448/*
 449 * 'copy_strings()' copies argument/environment strings from the old
 450 * processes's memory to the new process's stack.  The call to get_user_pages()
 451 * ensures the destination page is created and not swapped out.
 452 */
 453static int copy_strings(int argc, struct user_arg_ptr argv,
 454                        struct linux_binprm *bprm)
 455{
 456        struct page *kmapped_page = NULL;
 457        char *kaddr = NULL;
 458        unsigned long kpos = 0;
 459        int ret;
 460
 461        while (argc-- > 0) {
 462                const char __user *str;
 463                int len;
 464                unsigned long pos;
 465
 466                ret = -EFAULT;
 467                str = get_user_arg_ptr(argv, argc);
 468                if (IS_ERR(str))
 469                        goto out;
 470
 471                len = strnlen_user(str, MAX_ARG_STRLEN);
 472                if (!len)
 473                        goto out;
 474
 475                ret = -E2BIG;
 476                if (!valid_arg_len(bprm, len))
 477                        goto out;
 478
 479                /* We're going to work our way backwords. */
 480                pos = bprm->p;
 481                str += len;
 482                bprm->p -= len;
 483
 484                while (len > 0) {
 485                        int offset, bytes_to_copy;
 486
 487                        if (fatal_signal_pending(current)) {
 488                                ret = -ERESTARTNOHAND;
 489                                goto out;
 490                        }
 491                        cond_resched();
 492
 493                        offset = pos % PAGE_SIZE;
 494                        if (offset == 0)
 495                                offset = PAGE_SIZE;
 496
 497                        bytes_to_copy = offset;
 498                        if (bytes_to_copy > len)
 499                                bytes_to_copy = len;
 500
 501                        offset -= bytes_to_copy;
 502                        pos -= bytes_to_copy;
 503                        str -= bytes_to_copy;
 504                        len -= bytes_to_copy;
 505
 506                        if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 507                                struct page *page;
 508
 509                                page = get_arg_page(bprm, pos, 1);
 510                                if (!page) {
 511                                        ret = -E2BIG;
 512                                        goto out;
 513                                }
 514
 515                                if (kmapped_page) {
 516                                        flush_kernel_dcache_page(kmapped_page);
 517                                        kunmap(kmapped_page);
 518                                        put_arg_page(kmapped_page);
 519                                }
 520                                kmapped_page = page;
 521                                kaddr = kmap(kmapped_page);
 522                                kpos = pos & PAGE_MASK;
 523                                flush_arg_page(bprm, kpos, kmapped_page);
 524                        }
 525                        if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 526                                ret = -EFAULT;
 527                                goto out;
 528                        }
 529                }
 530        }
 531        ret = 0;
 532out:
 533        if (kmapped_page) {
 534                flush_kernel_dcache_page(kmapped_page);
 535                kunmap(kmapped_page);
 536                put_arg_page(kmapped_page);
 537        }
 538        return ret;
 539}
 540
 541/*
 542 * Like copy_strings, but get argv and its values from kernel memory.
 543 */
 544int copy_strings_kernel(int argc, const char *const *__argv,
 545                        struct linux_binprm *bprm)
 546{
 547        int r;
 548        mm_segment_t oldfs = get_fs();
 549        struct user_arg_ptr argv = {
 550                .ptr.native = (const char __user *const  __user *)__argv,
 551        };
 552
 553        set_fs(KERNEL_DS);
 554        r = copy_strings(argc, argv, bprm);
 555        set_fs(oldfs);
 556
 557        return r;
 558}
 559EXPORT_SYMBOL(copy_strings_kernel);
 560
 561#ifdef CONFIG_MMU
 562
 563/*
 564 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 565 * the binfmt code determines where the new stack should reside, we shift it to
 566 * its final location.  The process proceeds as follows:
 567 *
 568 * 1) Use shift to calculate the new vma endpoints.
 569 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 570 *    arguments passed to subsequent functions are consistent.
 571 * 3) Move vma's page tables to the new range.
 572 * 4) Free up any cleared pgd range.
 573 * 5) Shrink the vma to cover only the new range.
 574 */
 575static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 576{
 577        struct mm_struct *mm = vma->vm_mm;
 578        unsigned long old_start = vma->vm_start;
 579        unsigned long old_end = vma->vm_end;
 580        unsigned long length = old_end - old_start;
 581        unsigned long new_start = old_start - shift;
 582        unsigned long new_end = old_end - shift;
 583        struct mmu_gather tlb;
 584
 585        BUG_ON(new_start > new_end);
 586
 587        /*
 588         * ensure there are no vmas between where we want to go
 589         * and where we are
 590         */
 591        if (vma != find_vma(mm, new_start))
 592                return -EFAULT;
 593
 594        /*
 595         * cover the whole range: [new_start, old_end)
 596         */
 597        if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 598                return -ENOMEM;
 599
 600        /*
 601         * move the page tables downwards, on failure we rely on
 602         * process cleanup to remove whatever mess we made.
 603         */
 604        if (length != move_page_tables(vma, old_start,
 605                                       vma, new_start, length, false))
 606                return -ENOMEM;
 607
 608        lru_add_drain();
 609        tlb_gather_mmu(&tlb, mm, 0);
 610        if (new_end > old_start) {
 611                /*
 612                 * when the old and new regions overlap clear from new_end.
 613                 */
 614                free_pgd_range(&tlb, new_end, old_end, new_end,
 615                        vma->vm_next ? vma->vm_next->vm_start : 0);
 616        } else {
 617                /*
 618                 * otherwise, clean from old_start; this is done to not touch
 619                 * the address space in [new_end, old_start) some architectures
 620                 * have constraints on va-space that make this illegal (IA64) -
 621                 * for the others its just a little faster.
 622                 */
 623                free_pgd_range(&tlb, old_start, old_end, new_end,
 624                        vma->vm_next ? vma->vm_next->vm_start : 0);
 625        }
 626        tlb_finish_mmu(&tlb, new_end, old_end);
 627
 628        /*
 629         * Shrink the vma to just the new range.  Always succeeds.
 630         */
 631        vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 632
 633        return 0;
 634}
 635
 636/*
 637 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 638 * the stack is optionally relocated, and some extra space is added.
 639 */
 640int setup_arg_pages(struct linux_binprm *bprm,
 641                    unsigned long stack_top,
 642                    int executable_stack)
 643{
 644        unsigned long ret;
 645        unsigned long stack_shift;
 646        struct mm_struct *mm = current->mm;
 647        struct vm_area_struct *vma = bprm->vma;
 648        struct vm_area_struct *prev = NULL;
 649        unsigned long vm_flags;
 650        unsigned long stack_base;
 651        unsigned long stack_size;
 652        unsigned long stack_expand;
 653        unsigned long rlim_stack;
 654
 655#ifdef CONFIG_STACK_GROWSUP
 656        /* Limit stack size to 1GB */
 657        stack_base = rlimit_max(RLIMIT_STACK);
 658        if (stack_base > (1 << 30))
 659                stack_base = 1 << 30;
 660
 661        /* Make sure we didn't let the argument array grow too large. */
 662        if (vma->vm_end - vma->vm_start > stack_base)
 663                return -ENOMEM;
 664
 665        stack_base = PAGE_ALIGN(stack_top - stack_base);
 666
 667        stack_shift = vma->vm_start - stack_base;
 668        mm->arg_start = bprm->p - stack_shift;
 669        bprm->p = vma->vm_end - stack_shift;
 670#else
 671        stack_top = arch_align_stack(stack_top);
 672        stack_top = PAGE_ALIGN(stack_top);
 673
 674        if (unlikely(stack_top < mmap_min_addr) ||
 675            unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 676                return -ENOMEM;
 677
 678        stack_shift = vma->vm_end - stack_top;
 679
 680        bprm->p -= stack_shift;
 681        mm->arg_start = bprm->p;
 682#endif
 683
 684        if (bprm->loader)
 685                bprm->loader -= stack_shift;
 686        bprm->exec -= stack_shift;
 687
 688        down_write(&mm->mmap_sem);
 689        vm_flags = VM_STACK_FLAGS;
 690
 691        /*
 692         * Adjust stack execute permissions; explicitly enable for
 693         * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 694         * (arch default) otherwise.
 695         */
 696        if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 697                vm_flags |= VM_EXEC;
 698        else if (executable_stack == EXSTACK_DISABLE_X)
 699                vm_flags &= ~VM_EXEC;
 700        vm_flags |= mm->def_flags;
 701        vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 702
 703        ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 704                        vm_flags);
 705        if (ret)
 706                goto out_unlock;
 707        BUG_ON(prev != vma);
 708
 709        /* Move stack pages down in memory. */
 710        if (stack_shift) {
 711                ret = shift_arg_pages(vma, stack_shift);
 712                if (ret)
 713                        goto out_unlock;
 714        }
 715
 716        /* mprotect_fixup is overkill to remove the temporary stack flags */
 717        vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 718
 719        stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 720        stack_size = vma->vm_end - vma->vm_start;
 721        /*
 722         * Align this down to a page boundary as expand_stack
 723         * will align it up.
 724         */
 725        rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 726#ifdef CONFIG_STACK_GROWSUP
 727        if (stack_size + stack_expand > rlim_stack)
 728                stack_base = vma->vm_start + rlim_stack;
 729        else
 730                stack_base = vma->vm_end + stack_expand;
 731#else
 732        if (stack_size + stack_expand > rlim_stack)
 733                stack_base = vma->vm_end - rlim_stack;
 734        else
 735                stack_base = vma->vm_start - stack_expand;
 736#endif
 737        current->mm->start_stack = bprm->p;
 738        ret = expand_stack(vma, stack_base);
 739        if (ret)
 740                ret = -EFAULT;
 741
 742out_unlock:
 743        up_write(&mm->mmap_sem);
 744        return ret;
 745}
 746EXPORT_SYMBOL(setup_arg_pages);
 747
 748#endif /* CONFIG_MMU */
 749
 750struct file *open_exec(const char *name)
 751{
 752        struct file *file;
 753        int err;
 754        struct filename tmp = { .name = name };
 755        static const struct open_flags open_exec_flags = {
 756                .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 757                .acc_mode = MAY_EXEC | MAY_OPEN,
 758                .intent = LOOKUP_OPEN
 759        };
 760
 761        file = do_filp_open(AT_FDCWD, &tmp, &open_exec_flags, LOOKUP_FOLLOW);
 762        if (IS_ERR(file))
 763                goto out;
 764
 765        err = -EACCES;
 766        if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 767                goto exit;
 768
 769        if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 770                goto exit;
 771
 772        fsnotify_open(file);
 773
 774        err = deny_write_access(file);
 775        if (err)
 776                goto exit;
 777
 778out:
 779        return file;
 780
 781exit:
 782        fput(file);
 783        return ERR_PTR(err);
 784}
 785EXPORT_SYMBOL(open_exec);
 786
 787int kernel_read(struct file *file, loff_t offset,
 788                char *addr, unsigned long count)
 789{
 790        mm_segment_t old_fs;
 791        loff_t pos = offset;
 792        int result;
 793
 794        old_fs = get_fs();
 795        set_fs(get_ds());
 796        /* The cast to a user pointer is valid due to the set_fs() */
 797        result = vfs_read(file, (void __user *)addr, count, &pos);
 798        set_fs(old_fs);
 799        return result;
 800}
 801
 802EXPORT_SYMBOL(kernel_read);
 803
 804static int exec_mmap(struct mm_struct *mm)
 805{
 806        struct task_struct *tsk;
 807        struct mm_struct * old_mm, *active_mm;
 808
 809        /* Notify parent that we're no longer interested in the old VM */
 810        tsk = current;
 811        old_mm = current->mm;
 812        mm_release(tsk, old_mm);
 813
 814        if (old_mm) {
 815                sync_mm_rss(old_mm);
 816                /*
 817                 * Make sure that if there is a core dump in progress
 818                 * for the old mm, we get out and die instead of going
 819                 * through with the exec.  We must hold mmap_sem around
 820                 * checking core_state and changing tsk->mm.
 821                 */
 822                down_read(&old_mm->mmap_sem);
 823                if (unlikely(old_mm->core_state)) {
 824                        up_read(&old_mm->mmap_sem);
 825                        return -EINTR;
 826                }
 827        }
 828        task_lock(tsk);
 829        active_mm = tsk->active_mm;
 830        tsk->mm = mm;
 831        tsk->active_mm = mm;
 832        activate_mm(active_mm, mm);
 833        task_unlock(tsk);
 834        arch_pick_mmap_layout(mm);
 835        if (old_mm) {
 836                up_read(&old_mm->mmap_sem);
 837                BUG_ON(active_mm != old_mm);
 838                setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
 839                mm_update_next_owner(old_mm);
 840                mmput(old_mm);
 841                return 0;
 842        }
 843        mmdrop(active_mm);
 844        return 0;
 845}
 846
 847/*
 848 * This function makes sure the current process has its own signal table,
 849 * so that flush_signal_handlers can later reset the handlers without
 850 * disturbing other processes.  (Other processes might share the signal
 851 * table via the CLONE_SIGHAND option to clone().)
 852 */
 853static int de_thread(struct task_struct *tsk)
 854{
 855        struct signal_struct *sig = tsk->signal;
 856        struct sighand_struct *oldsighand = tsk->sighand;
 857        spinlock_t *lock = &oldsighand->siglock;
 858
 859        if (thread_group_empty(tsk))
 860                goto no_thread_group;
 861
 862        /*
 863         * Kill all other threads in the thread group.
 864         */
 865        spin_lock_irq(lock);
 866        if (signal_group_exit(sig)) {
 867                /*
 868                 * Another group action in progress, just
 869                 * return so that the signal is processed.
 870                 */
 871                spin_unlock_irq(lock);
 872                return -EAGAIN;
 873        }
 874
 875        sig->group_exit_task = tsk;
 876        sig->notify_count = zap_other_threads(tsk);
 877        if (!thread_group_leader(tsk))
 878                sig->notify_count--;
 879
 880        while (sig->notify_count) {
 881                __set_current_state(TASK_KILLABLE);
 882                spin_unlock_irq(lock);
 883                schedule();
 884                if (unlikely(__fatal_signal_pending(tsk)))
 885                        goto killed;
 886                spin_lock_irq(lock);
 887        }
 888        spin_unlock_irq(lock);
 889
 890        /*
 891         * At this point all other threads have exited, all we have to
 892         * do is to wait for the thread group leader to become inactive,
 893         * and to assume its PID:
 894         */
 895        if (!thread_group_leader(tsk)) {
 896                struct task_struct *leader = tsk->group_leader;
 897
 898                sig->notify_count = -1; /* for exit_notify() */
 899                for (;;) {
 900                        write_lock_irq(&tasklist_lock);
 901                        if (likely(leader->exit_state))
 902                                break;
 903                        __set_current_state(TASK_KILLABLE);
 904                        write_unlock_irq(&tasklist_lock);
 905                        schedule();
 906                        if (unlikely(__fatal_signal_pending(tsk)))
 907                                goto killed;
 908                }
 909
 910                /*
 911                 * The only record we have of the real-time age of a
 912                 * process, regardless of execs it's done, is start_time.
 913                 * All the past CPU time is accumulated in signal_struct
 914                 * from sister threads now dead.  But in this non-leader
 915                 * exec, nothing survives from the original leader thread,
 916                 * whose birth marks the true age of this process now.
 917                 * When we take on its identity by switching to its PID, we
 918                 * also take its birthdate (always earlier than our own).
 919                 */
 920                tsk->start_time = leader->start_time;
 921
 922                BUG_ON(!same_thread_group(leader, tsk));
 923                BUG_ON(has_group_leader_pid(tsk));
 924                /*
 925                 * An exec() starts a new thread group with the
 926                 * TGID of the previous thread group. Rehash the
 927                 * two threads with a switched PID, and release
 928                 * the former thread group leader:
 929                 */
 930
 931                /* Become a process group leader with the old leader's pid.
 932                 * The old leader becomes a thread of the this thread group.
 933                 * Note: The old leader also uses this pid until release_task
 934                 *       is called.  Odd but simple and correct.
 935                 */
 936                detach_pid(tsk, PIDTYPE_PID);
 937                tsk->pid = leader->pid;
 938                attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 939                transfer_pid(leader, tsk, PIDTYPE_PGID);
 940                transfer_pid(leader, tsk, PIDTYPE_SID);
 941
 942                list_replace_rcu(&leader->tasks, &tsk->tasks);
 943                list_replace_init(&leader->sibling, &tsk->sibling);
 944
 945                tsk->group_leader = tsk;
 946                leader->group_leader = tsk;
 947
 948                tsk->exit_signal = SIGCHLD;
 949                leader->exit_signal = -1;
 950
 951                BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 952                leader->exit_state = EXIT_DEAD;
 953
 954                /*
 955                 * We are going to release_task()->ptrace_unlink() silently,
 956                 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
 957                 * the tracer wont't block again waiting for this thread.
 958                 */
 959                if (unlikely(leader->ptrace))
 960                        __wake_up_parent(leader, leader->parent);
 961                write_unlock_irq(&tasklist_lock);
 962
 963                release_task(leader);
 964        }
 965
 966        sig->group_exit_task = NULL;
 967        sig->notify_count = 0;
 968
 969no_thread_group:
 970        /* we have changed execution domain */
 971        tsk->exit_signal = SIGCHLD;
 972
 973        exit_itimers(sig);
 974        flush_itimer_signals();
 975
 976        if (atomic_read(&oldsighand->count) != 1) {
 977                struct sighand_struct *newsighand;
 978                /*
 979                 * This ->sighand is shared with the CLONE_SIGHAND
 980                 * but not CLONE_THREAD task, switch to the new one.
 981                 */
 982                newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 983                if (!newsighand)
 984                        return -ENOMEM;
 985
 986                atomic_set(&newsighand->count, 1);
 987                memcpy(newsighand->action, oldsighand->action,
 988                       sizeof(newsighand->action));
 989
 990                write_lock_irq(&tasklist_lock);
 991                spin_lock(&oldsighand->siglock);
 992                rcu_assign_pointer(tsk->sighand, newsighand);
 993                spin_unlock(&oldsighand->siglock);
 994                write_unlock_irq(&tasklist_lock);
 995
 996                __cleanup_sighand(oldsighand);
 997        }
 998
 999        BUG_ON(!thread_group_leader(tsk));
1000        return 0;
1001
1002killed:
1003        /* protects against exit_notify() and __exit_signal() */
1004        read_lock(&tasklist_lock);
1005        sig->group_exit_task = NULL;
1006        sig->notify_count = 0;
1007        read_unlock(&tasklist_lock);
1008        return -EAGAIN;
1009}
1010
1011char *get_task_comm(char *buf, struct task_struct *tsk)
1012{
1013        /* buf must be at least sizeof(tsk->comm) in size */
1014        task_lock(tsk);
1015        strncpy(buf, tsk->comm, sizeof(tsk->comm));
1016        task_unlock(tsk);
1017        return buf;
1018}
1019EXPORT_SYMBOL_GPL(get_task_comm);
1020
1021/*
1022 * These functions flushes out all traces of the currently running executable
1023 * so that a new one can be started
1024 */
1025
1026void set_task_comm(struct task_struct *tsk, char *buf)
1027{
1028        task_lock(tsk);
1029
1030        trace_task_rename(tsk, buf);
1031
1032        /*
1033         * Threads may access current->comm without holding
1034         * the task lock, so write the string carefully.
1035         * Readers without a lock may see incomplete new
1036         * names but are safe from non-terminating string reads.
1037         */
1038        memset(tsk->comm, 0, TASK_COMM_LEN);
1039        wmb();
1040        strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1041        task_unlock(tsk);
1042        perf_event_comm(tsk);
1043}
1044
1045static void filename_to_taskname(char *tcomm, const char *fn, unsigned int len)
1046{
1047        int i, ch;
1048
1049        /* Copies the binary name from after last slash */
1050        for (i = 0; (ch = *(fn++)) != '\0';) {
1051                if (ch == '/')
1052                        i = 0; /* overwrite what we wrote */
1053                else
1054                        if (i < len - 1)
1055                                tcomm[i++] = ch;
1056        }
1057        tcomm[i] = '\0';
1058}
1059
1060int flush_old_exec(struct linux_binprm * bprm)
1061{
1062        int retval;
1063
1064        /*
1065         * Make sure we have a private signal table and that
1066         * we are unassociated from the previous thread group.
1067         */
1068        retval = de_thread(current);
1069        if (retval)
1070                goto out;
1071
1072        set_mm_exe_file(bprm->mm, bprm->file);
1073
1074        filename_to_taskname(bprm->tcomm, bprm->filename, sizeof(bprm->tcomm));
1075        /*
1076         * Release all of the old mmap stuff
1077         */
1078        acct_arg_size(bprm, 0);
1079        retval = exec_mmap(bprm->mm);
1080        if (retval)
1081                goto out;
1082
1083        bprm->mm = NULL;                /* We're using it now */
1084
1085        set_fs(USER_DS);
1086        current->flags &=
1087                ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | PF_NOFREEZE);
1088        flush_thread();
1089        current->personality &= ~bprm->per_clear;
1090
1091        return 0;
1092
1093out:
1094        return retval;
1095}
1096EXPORT_SYMBOL(flush_old_exec);
1097
1098void would_dump(struct linux_binprm *bprm, struct file *file)
1099{
1100        if (inode_permission(file->f_path.dentry->d_inode, MAY_READ) < 0)
1101                bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1102}
1103EXPORT_SYMBOL(would_dump);
1104
1105void setup_new_exec(struct linux_binprm * bprm)
1106{
1107        arch_pick_mmap_layout(current->mm);
1108
1109        /* This is the point of no return */
1110        current->sas_ss_sp = current->sas_ss_size = 0;
1111
1112        if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1113                set_dumpable(current->mm, SUID_DUMPABLE_ENABLED);
1114        else
1115                set_dumpable(current->mm, suid_dumpable);
1116
1117        set_task_comm(current, bprm->tcomm);
1118
1119        /* Set the new mm task size. We have to do that late because it may
1120         * depend on TIF_32BIT which is only updated in flush_thread() on
1121         * some architectures like powerpc
1122         */
1123        current->mm->task_size = TASK_SIZE;
1124
1125        /* install the new credentials */
1126        if (!uid_eq(bprm->cred->uid, current_euid()) ||
1127            !gid_eq(bprm->cred->gid, current_egid())) {
1128                current->pdeath_signal = 0;
1129        } else {
1130                would_dump(bprm, bprm->file);
1131                if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1132                        set_dumpable(current->mm, suid_dumpable);
1133        }
1134
1135        /*
1136         * Flush performance counters when crossing a
1137         * security domain:
1138         */
1139        if (!get_dumpable(current->mm))
1140                perf_event_exit_task(current);
1141
1142        /* An exec changes our domain. We are no longer part of the thread
1143           group */
1144
1145        current->self_exec_id++;
1146                        
1147        flush_signal_handlers(current, 0);
1148        do_close_on_exec(current->files);
1149}
1150EXPORT_SYMBOL(setup_new_exec);
1151
1152/*
1153 * Prepare credentials and lock ->cred_guard_mutex.
1154 * install_exec_creds() commits the new creds and drops the lock.
1155 * Or, if exec fails before, free_bprm() should release ->cred and
1156 * and unlock.
1157 */
1158int prepare_bprm_creds(struct linux_binprm *bprm)
1159{
1160        if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1161                return -ERESTARTNOINTR;
1162
1163        bprm->cred = prepare_exec_creds();
1164        if (likely(bprm->cred))
1165                return 0;
1166
1167        mutex_unlock(&current->signal->cred_guard_mutex);
1168        return -ENOMEM;
1169}
1170
1171void free_bprm(struct linux_binprm *bprm)
1172{
1173        free_arg_pages(bprm);
1174        if (bprm->cred) {
1175                mutex_unlock(&current->signal->cred_guard_mutex);
1176                abort_creds(bprm->cred);
1177        }
1178        /* If a binfmt changed the interp, free it. */
1179        if (bprm->interp != bprm->filename)
1180                kfree(bprm->interp);
1181        kfree(bprm);
1182}
1183
1184int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1185{
1186        /* If a binfmt changed the interp, free it first. */
1187        if (bprm->interp != bprm->filename)
1188                kfree(bprm->interp);
1189        bprm->interp = kstrdup(interp, GFP_KERNEL);
1190        if (!bprm->interp)
1191                return -ENOMEM;
1192        return 0;
1193}
1194EXPORT_SYMBOL(bprm_change_interp);
1195
1196/*
1197 * install the new credentials for this executable
1198 */
1199void install_exec_creds(struct linux_binprm *bprm)
1200{
1201        security_bprm_committing_creds(bprm);
1202
1203        commit_creds(bprm->cred);
1204        bprm->cred = NULL;
1205        /*
1206         * cred_guard_mutex must be held at least to this point to prevent
1207         * ptrace_attach() from altering our determination of the task's
1208         * credentials; any time after this it may be unlocked.
1209         */
1210        security_bprm_committed_creds(bprm);
1211        mutex_unlock(&current->signal->cred_guard_mutex);
1212}
1213EXPORT_SYMBOL(install_exec_creds);
1214
1215/*
1216 * determine how safe it is to execute the proposed program
1217 * - the caller must hold ->cred_guard_mutex to protect against
1218 *   PTRACE_ATTACH
1219 */
1220static int check_unsafe_exec(struct linux_binprm *bprm)
1221{
1222        struct task_struct *p = current, *t;
1223        unsigned n_fs;
1224        int res = 0;
1225
1226        if (p->ptrace) {
1227                if (p->ptrace & PT_PTRACE_CAP)
1228                        bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1229                else
1230                        bprm->unsafe |= LSM_UNSAFE_PTRACE;
1231        }
1232
1233        /*
1234         * This isn't strictly necessary, but it makes it harder for LSMs to
1235         * mess up.
1236         */
1237        if (current->no_new_privs)
1238                bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1239
1240        n_fs = 1;
1241        spin_lock(&p->fs->lock);
1242        rcu_read_lock();
1243        for (t = next_thread(p); t != p; t = next_thread(t)) {
1244                if (t->fs == p->fs)
1245                        n_fs++;
1246        }
1247        rcu_read_unlock();
1248
1249        if (p->fs->users > n_fs) {
1250                bprm->unsafe |= LSM_UNSAFE_SHARE;
1251        } else {
1252                res = -EAGAIN;
1253                if (!p->fs->in_exec) {
1254                        p->fs->in_exec = 1;
1255                        res = 1;
1256                }
1257        }
1258        spin_unlock(&p->fs->lock);
1259
1260        return res;
1261}
1262
1263/* 
1264 * Fill the binprm structure from the inode. 
1265 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1266 *
1267 * This may be called multiple times for binary chains (scripts for example).
1268 */
1269int prepare_binprm(struct linux_binprm *bprm)
1270{
1271        umode_t mode;
1272        struct inode * inode = bprm->file->f_path.dentry->d_inode;
1273        int retval;
1274
1275        mode = inode->i_mode;
1276        if (bprm->file->f_op == NULL)
1277                return -EACCES;
1278
1279        /* clear any previous set[ug]id data from a previous binary */
1280        bprm->cred->euid = current_euid();
1281        bprm->cred->egid = current_egid();
1282
1283        if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID) &&
1284            !current->no_new_privs) {
1285                /* Set-uid? */
1286                if (mode & S_ISUID) {
1287                        if (!kuid_has_mapping(bprm->cred->user_ns, inode->i_uid))
1288                                return -EPERM;
1289                        bprm->per_clear |= PER_CLEAR_ON_SETID;
1290                        bprm->cred->euid = inode->i_uid;
1291
1292                }
1293
1294                /* Set-gid? */
1295                /*
1296                 * If setgid is set but no group execute bit then this
1297                 * is a candidate for mandatory locking, not a setgid
1298                 * executable.
1299                 */
1300                if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1301                        if (!kgid_has_mapping(bprm->cred->user_ns, inode->i_gid))
1302                                return -EPERM;
1303                        bprm->per_clear |= PER_CLEAR_ON_SETID;
1304                        bprm->cred->egid = inode->i_gid;
1305                }
1306        }
1307
1308        /* fill in binprm security blob */
1309        retval = security_bprm_set_creds(bprm);
1310        if (retval)
1311                return retval;
1312        bprm->cred_prepared = 1;
1313
1314        memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1315        return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1316}
1317
1318EXPORT_SYMBOL(prepare_binprm);
1319
1320/*
1321 * Arguments are '\0' separated strings found at the location bprm->p
1322 * points to; chop off the first by relocating brpm->p to right after
1323 * the first '\0' encountered.
1324 */
1325int remove_arg_zero(struct linux_binprm *bprm)
1326{
1327        int ret = 0;
1328        unsigned long offset;
1329        char *kaddr;
1330        struct page *page;
1331
1332        if (!bprm->argc)
1333                return 0;
1334
1335        do {
1336                offset = bprm->p & ~PAGE_MASK;
1337                page = get_arg_page(bprm, bprm->p, 0);
1338                if (!page) {
1339                        ret = -EFAULT;
1340                        goto out;
1341                }
1342                kaddr = kmap_atomic(page);
1343
1344                for (; offset < PAGE_SIZE && kaddr[offset];
1345                                offset++, bprm->p++)
1346                        ;
1347
1348                kunmap_atomic(kaddr);
1349                put_arg_page(page);
1350
1351                if (offset == PAGE_SIZE)
1352                        free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1353        } while (offset == PAGE_SIZE);
1354
1355        bprm->p++;
1356        bprm->argc--;
1357        ret = 0;
1358
1359out:
1360        return ret;
1361}
1362EXPORT_SYMBOL(remove_arg_zero);
1363
1364/*
1365 * cycle the list of binary formats handler, until one recognizes the image
1366 */
1367int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1368{
1369        unsigned int depth = bprm->recursion_depth;
1370        int try,retval;
1371        struct linux_binfmt *fmt;
1372        pid_t old_pid, old_vpid;
1373
1374        retval = security_bprm_check(bprm);
1375        if (retval)
1376                return retval;
1377
1378        retval = audit_bprm(bprm);
1379        if (retval)
1380                return retval;
1381
1382        /* Need to fetch pid before load_binary changes it */
1383        old_pid = current->pid;
1384        rcu_read_lock();
1385        old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1386        rcu_read_unlock();
1387
1388        retval = -ENOENT;
1389        for (try=0; try<2; try++) {
1390                read_lock(&binfmt_lock);
1391                list_for_each_entry(fmt, &formats, lh) {
1392                        int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1393                        if (!fn)
1394                                continue;
1395                        if (!try_module_get(fmt->module))
1396                                continue;
1397                        read_unlock(&binfmt_lock);
1398                        retval = fn(bprm, regs);
1399                        /*
1400                         * Restore the depth counter to its starting value
1401                         * in this call, so we don't have to rely on every
1402                         * load_binary function to restore it on return.
1403                         */
1404                        bprm->recursion_depth = depth;
1405                        if (retval >= 0) {
1406                                if (depth == 0) {
1407                                        trace_sched_process_exec(current, old_pid, bprm);
1408                                        ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1409                                }
1410                                put_binfmt(fmt);
1411                                allow_write_access(bprm->file);
1412                                if (bprm->file)
1413                                        fput(bprm->file);
1414                                bprm->file = NULL;
1415                                current->did_exec = 1;
1416                                proc_exec_connector(current);
1417                                return retval;
1418                        }
1419                        read_lock(&binfmt_lock);
1420                        put_binfmt(fmt);
1421                        if (retval != -ENOEXEC || bprm->mm == NULL)
1422                                break;
1423                        if (!bprm->file) {
1424                                read_unlock(&binfmt_lock);
1425                                return retval;
1426                        }
1427                }
1428                read_unlock(&binfmt_lock);
1429#ifdef CONFIG_MODULES
1430                if (retval != -ENOEXEC || bprm->mm == NULL) {
1431                        break;
1432                } else {
1433#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1434                        if (printable(bprm->buf[0]) &&
1435                            printable(bprm->buf[1]) &&
1436                            printable(bprm->buf[2]) &&
1437                            printable(bprm->buf[3]))
1438                                break; /* -ENOEXEC */
1439                        if (try)
1440                                break; /* -ENOEXEC */
1441                        request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1442                }
1443#else
1444                break;
1445#endif
1446        }
1447        return retval;
1448}
1449
1450EXPORT_SYMBOL(search_binary_handler);
1451
1452/*
1453 * sys_execve() executes a new program.
1454 */
1455static int do_execve_common(const char *filename,
1456                                struct user_arg_ptr argv,
1457                                struct user_arg_ptr envp,
1458                                struct pt_regs *regs)
1459{
1460        struct linux_binprm *bprm;
1461        struct file *file;
1462        struct files_struct *displaced;
1463        bool clear_in_exec;
1464        int retval;
1465        const struct cred *cred = current_cred();
1466
1467        /*
1468         * We move the actual failure in case of RLIMIT_NPROC excess from
1469         * set*uid() to execve() because too many poorly written programs
1470         * don't check setuid() return code.  Here we additionally recheck
1471         * whether NPROC limit is still exceeded.
1472         */
1473        if ((current->flags & PF_NPROC_EXCEEDED) &&
1474            atomic_read(&cred->user->processes) > rlimit(RLIMIT_NPROC)) {
1475                retval = -EAGAIN;
1476                goto out_ret;
1477        }
1478
1479        /* We're below the limit (still or again), so we don't want to make
1480         * further execve() calls fail. */
1481        current->flags &= ~PF_NPROC_EXCEEDED;
1482
1483        retval = unshare_files(&displaced);
1484        if (retval)
1485                goto out_ret;
1486
1487        retval = -ENOMEM;
1488        bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1489        if (!bprm)
1490                goto out_files;
1491
1492        retval = prepare_bprm_creds(bprm);
1493        if (retval)
1494                goto out_free;
1495
1496        retval = check_unsafe_exec(bprm);
1497        if (retval < 0)
1498                goto out_free;
1499        clear_in_exec = retval;
1500        current->in_execve = 1;
1501
1502        file = open_exec(filename);
1503        retval = PTR_ERR(file);
1504        if (IS_ERR(file))
1505                goto out_unmark;
1506
1507        sched_exec();
1508
1509        bprm->file = file;
1510        bprm->filename = filename;
1511        bprm->interp = filename;
1512
1513        retval = bprm_mm_init(bprm);
1514        if (retval)
1515                goto out_file;
1516
1517        bprm->argc = count(argv, MAX_ARG_STRINGS);
1518        if ((retval = bprm->argc) < 0)
1519                goto out;
1520
1521        bprm->envc = count(envp, MAX_ARG_STRINGS);
1522        if ((retval = bprm->envc) < 0)
1523                goto out;
1524
1525        retval = prepare_binprm(bprm);
1526        if (retval < 0)
1527                goto out;
1528
1529        retval = copy_strings_kernel(1, &bprm->filename, bprm);
1530        if (retval < 0)
1531                goto out;
1532
1533        bprm->exec = bprm->p;
1534        retval = copy_strings(bprm->envc, envp, bprm);
1535        if (retval < 0)
1536                goto out;
1537
1538        retval = copy_strings(bprm->argc, argv, bprm);
1539        if (retval < 0)
1540                goto out;
1541
1542        retval = search_binary_handler(bprm,regs);
1543        if (retval < 0)
1544                goto out;
1545
1546        /* execve succeeded */
1547        current->fs->in_exec = 0;
1548        current->in_execve = 0;
1549        acct_update_integrals(current);
1550        free_bprm(bprm);
1551        if (displaced)
1552                put_files_struct(displaced);
1553        return retval;
1554
1555out:
1556        if (bprm->mm) {
1557                acct_arg_size(bprm, 0);
1558                mmput(bprm->mm);
1559        }
1560
1561out_file:
1562        if (bprm->file) {
1563                allow_write_access(bprm->file);
1564                fput(bprm->file);
1565        }
1566
1567out_unmark:
1568        if (clear_in_exec)
1569                current->fs->in_exec = 0;
1570        current->in_execve = 0;
1571
1572out_free:
1573        free_bprm(bprm);
1574
1575out_files:
1576        if (displaced)
1577                reset_files_struct(displaced);
1578out_ret:
1579        return retval;
1580}
1581
1582int do_execve(const char *filename,
1583        const char __user *const __user *__argv,
1584        const char __user *const __user *__envp,
1585        struct pt_regs *regs)
1586{
1587        struct user_arg_ptr argv = { .ptr.native = __argv };
1588        struct user_arg_ptr envp = { .ptr.native = __envp };
1589        return do_execve_common(filename, argv, envp, regs);
1590}
1591
1592#ifdef CONFIG_COMPAT
1593int compat_do_execve(const char *filename,
1594        const compat_uptr_t __user *__argv,
1595        const compat_uptr_t __user *__envp,
1596        struct pt_regs *regs)
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, regs);
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_DUMPABLE_DISABLED:
1648                clear_bit(MMF_DUMPABLE, &mm->flags);
1649                smp_wmb();
1650                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1651                break;
1652        case SUID_DUMPABLE_ENABLED:
1653                set_bit(MMF_DUMPABLE, &mm->flags);
1654                smp_wmb();
1655                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1656                break;
1657        case SUID_DUMPABLE_SAFE:
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_DUMPABLE_ENABLED) ? SUID_DUMPABLE_SAFE : ret;
1671}
1672
1673int get_dumpable(struct mm_struct *mm)
1674{
1675        return __get_dumpable(mm->flags);
1676}
1677
1678#ifdef __ARCH_WANT_SYS_EXECVE
1679SYSCALL_DEFINE3(execve,
1680                const char __user *, filename,
1681                const char __user *const __user *, argv,
1682                const char __user *const __user *, envp)
1683{
1684        struct filename *path = getname(filename);
1685        int error = PTR_ERR(path);
1686        if (!IS_ERR(path)) {
1687                error = do_execve(path->name, argv, envp, current_pt_regs());
1688                putname(path);
1689        }
1690        return error;
1691}
1692#ifdef CONFIG_COMPAT
1693asmlinkage long compat_sys_execve(const char __user * filename,
1694        const compat_uptr_t __user * argv,
1695        const compat_uptr_t __user * envp)
1696{
1697        struct filename *path = getname(filename);
1698        int error = PTR_ERR(path);
1699        if (!IS_ERR(path)) {
1700                error = compat_do_execve(path->name, argv, envp,
1701                                                        current_pt_regs());
1702                putname(path);
1703        }
1704        return error;
1705}
1706#endif
1707#endif
1708
1709#ifdef __ARCH_WANT_KERNEL_EXECVE
1710int kernel_execve(const char *filename,
1711                  const char *const argv[],
1712                  const char *const envp[])
1713{
1714        struct pt_regs *p = current_pt_regs();
1715        int ret;
1716
1717        ret = do_execve(filename,
1718                        (const char __user *const __user *)argv,
1719                        (const char __user *const __user *)envp, p);
1720        if (ret < 0)
1721                return ret;
1722
1723        /*
1724         * We were successful.  We won't be returning to our caller, but
1725         * instead to user space by manipulating the kernel stack.
1726         */
1727        ret_from_kernel_execve(p);
1728}
1729#endif
1730
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