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/vmacache.h>
  30#include <linux/stat.h>
  31#include <linux/fcntl.h>
  32#include <linux/swap.h>
  33#include <linux/string.h>
  34#include <linux/init.h>
  35#include <linux/pagemap.h>
  36#include <linux/perf_event.h>
  37#include <linux/highmem.h>
  38#include <linux/spinlock.h>
  39#include <linux/key.h>
  40#include <linux/personality.h>
  41#include <linux/binfmts.h>
  42#include <linux/utsname.h>
  43#include <linux/pid_namespace.h>
  44#include <linux/module.h>
  45#include <linux/namei.h>
  46#include <linux/mount.h>
  47#include <linux/security.h>
  48#include <linux/syscalls.h>
  49#include <linux/tsacct_kern.h>
  50#include <linux/cn_proc.h>
  51#include <linux/audit.h>
  52#include <linux/tracehook.h>
  53#include <linux/kmod.h>
  54#include <linux/fsnotify.h>
  55#include <linux/fs_struct.h>
  56#include <linux/pipe_fs_i.h>
  57#include <linux/oom.h>
  58#include <linux/compat.h>
  59#include <linux/vmalloc.h>
  60
  61#include <asm/uaccess.h>
  62#include <asm/mmu_context.h>
  63#include <asm/tlb.h>
  64
  65#include <trace/events/task.h>
  66#include "internal.h"
  67
  68#include <trace/events/sched.h>
  69
  70int suid_dumpable = 0;
  71
  72static LIST_HEAD(formats);
  73static DEFINE_RWLOCK(binfmt_lock);
  74
  75void __register_binfmt(struct linux_binfmt * fmt, int insert)
  76{
  77        BUG_ON(!fmt);
  78        if (WARN_ON(!fmt->load_binary))
  79                return;
  80        write_lock(&binfmt_lock);
  81        insert ? list_add(&fmt->lh, &formats) :
  82                 list_add_tail(&fmt->lh, &formats);
  83        write_unlock(&binfmt_lock);
  84}
  85
  86EXPORT_SYMBOL(__register_binfmt);
  87
  88void unregister_binfmt(struct linux_binfmt * fmt)
  89{
  90        write_lock(&binfmt_lock);
  91        list_del(&fmt->lh);
  92        write_unlock(&binfmt_lock);
  93}
  94
  95EXPORT_SYMBOL(unregister_binfmt);
  96
  97static inline void put_binfmt(struct linux_binfmt * fmt)
  98{
  99        module_put(fmt->module);
 100}
 101
 102bool path_noexec(const struct path *path)
 103{
 104        return (path->mnt->mnt_flags & MNT_NOEXEC) ||
 105               (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
 106}
 107
 108#ifdef CONFIG_USELIB
 109/*
 110 * Note that a shared library must be both readable and executable due to
 111 * security reasons.
 112 *
 113 * Also note that we take the address to load from from the file itself.
 114 */
 115SYSCALL_DEFINE1(uselib, const char __user *, library)
 116{
 117        struct linux_binfmt *fmt;
 118        struct file *file;
 119        struct filename *tmp = getname(library);
 120        int error = PTR_ERR(tmp);
 121        static const struct open_flags uselib_flags = {
 122                .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 123                .acc_mode = MAY_READ | MAY_EXEC,
 124                .intent = LOOKUP_OPEN,
 125                .lookup_flags = LOOKUP_FOLLOW,
 126        };
 127
 128        if (IS_ERR(tmp))
 129                goto out;
 130
 131        file = do_filp_open(AT_FDCWD, tmp, &uselib_flags);
 132        putname(tmp);
 133        error = PTR_ERR(file);
 134        if (IS_ERR(file))
 135                goto out;
 136
 137        error = -EINVAL;
 138        if (!S_ISREG(file_inode(file)->i_mode))
 139                goto exit;
 140
 141        error = -EACCES;
 142        if (path_noexec(&file->f_path))
 143                goto exit;
 144
 145        fsnotify_open(file);
 146
 147        error = -ENOEXEC;
 148
 149        read_lock(&binfmt_lock);
 150        list_for_each_entry(fmt, &formats, lh) {
 151                if (!fmt->load_shlib)
 152                        continue;
 153                if (!try_module_get(fmt->module))
 154                        continue;
 155                read_unlock(&binfmt_lock);
 156                error = fmt->load_shlib(file);
 157                read_lock(&binfmt_lock);
 158                put_binfmt(fmt);
 159                if (error != -ENOEXEC)
 160                        break;
 161        }
 162        read_unlock(&binfmt_lock);
 163exit:
 164        fput(file);
 165out:
 166        return error;
 167}
 168#endif /* #ifdef CONFIG_USELIB */
 169
 170#ifdef CONFIG_MMU
 171/*
 172 * The nascent bprm->mm is not visible until exec_mmap() but it can
 173 * use a lot of memory, account these pages in current->mm temporary
 174 * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 175 * change the counter back via acct_arg_size(0).
 176 */
 177static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 178{
 179        struct mm_struct *mm = current->mm;
 180        long diff = (long)(pages - bprm->vma_pages);
 181
 182        if (!mm || !diff)
 183                return;
 184
 185        bprm->vma_pages = pages;
 186        add_mm_counter(mm, MM_ANONPAGES, diff);
 187}
 188
 189static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 190                int write)
 191{
 192        struct page *page;
 193        int ret;
 194
 195#ifdef CONFIG_STACK_GROWSUP
 196        if (write) {
 197                ret = expand_downwards(bprm->vma, pos);
 198                if (ret < 0)
 199                        return NULL;
 200        }
 201#endif
 202        /*
 203         * We are doing an exec().  'current' is the process
 204         * doing the exec and bprm->mm is the new process's mm.
 205         */
 206        ret = get_user_pages_remote(current, bprm->mm, pos, 1, write,
 207                        1, &page, NULL);
 208        if (ret <= 0)
 209                return NULL;
 210
 211        if (write) {
 212                unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 213                struct rlimit *rlim;
 214
 215                acct_arg_size(bprm, size / PAGE_SIZE);
 216
 217                /*
 218                 * We've historically supported up to 32 pages (ARG_MAX)
 219                 * of argument strings even with small stacks
 220                 */
 221                if (size <= ARG_MAX)
 222                        return page;
 223
 224                /*
 225                 * Limit to 1/4-th the stack size for the argv+env strings.
 226                 * This ensures that:
 227                 *  - the remaining binfmt code will not run out of stack space,
 228                 *  - the program will have a reasonable amount of stack left
 229                 *    to work from.
 230                 */
 231                rlim = current->signal->rlim;
 232                if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 233                        put_page(page);
 234                        return NULL;
 235                }
 236        }
 237
 238        return page;
 239}
 240
 241static void put_arg_page(struct page *page)
 242{
 243        put_page(page);
 244}
 245
 246static void free_arg_page(struct linux_binprm *bprm, int i)
 247{
 248}
 249
 250static void free_arg_pages(struct linux_binprm *bprm)
 251{
 252}
 253
 254static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 255                struct page *page)
 256{
 257        flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 258}
 259
 260static int __bprm_mm_init(struct linux_binprm *bprm)
 261{
 262        int err;
 263        struct vm_area_struct *vma = NULL;
 264        struct mm_struct *mm = bprm->mm;
 265
 266        bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 267        if (!vma)
 268                return -ENOMEM;
 269
 270        down_write(&mm->mmap_sem);
 271        vma->vm_mm = mm;
 272
 273        /*
 274         * Place the stack at the largest stack address the architecture
 275         * supports. Later, we'll move this to an appropriate place. We don't
 276         * use STACK_TOP because that can depend on attributes which aren't
 277         * configured yet.
 278         */
 279        BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 280        vma->vm_end = STACK_TOP_MAX;
 281        vma->vm_start = vma->vm_end - PAGE_SIZE;
 282        vma->vm_flags = VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 283        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 284        INIT_LIST_HEAD(&vma->anon_vma_chain);
 285
 286        err = insert_vm_struct(mm, vma);
 287        if (err)
 288                goto err;
 289
 290        mm->stack_vm = mm->total_vm = 1;
 291        arch_bprm_mm_init(mm, vma);
 292        up_write(&mm->mmap_sem);
 293        bprm->p = vma->vm_end - sizeof(void *);
 294        return 0;
 295err:
 296        up_write(&mm->mmap_sem);
 297        bprm->vma = NULL;
 298        kmem_cache_free(vm_area_cachep, vma);
 299        return err;
 300}
 301
 302static bool valid_arg_len(struct linux_binprm *bprm, long len)
 303{
 304        return len <= MAX_ARG_STRLEN;
 305}
 306
 307#else
 308
 309static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 310{
 311}
 312
 313static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 314                int write)
 315{
 316        struct page *page;
 317
 318        page = bprm->page[pos / PAGE_SIZE];
 319        if (!page && write) {
 320                page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 321                if (!page)
 322                        return NULL;
 323                bprm->page[pos / PAGE_SIZE] = page;
 324        }
 325
 326        return page;
 327}
 328
 329static void put_arg_page(struct page *page)
 330{
 331}
 332
 333static void free_arg_page(struct linux_binprm *bprm, int i)
 334{
 335        if (bprm->page[i]) {
 336                __free_page(bprm->page[i]);
 337                bprm->page[i] = NULL;
 338        }
 339}
 340
 341static void free_arg_pages(struct linux_binprm *bprm)
 342{
 343        int i;
 344
 345        for (i = 0; i < MAX_ARG_PAGES; i++)
 346                free_arg_page(bprm, i);
 347}
 348
 349static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 350                struct page *page)
 351{
 352}
 353
 354static int __bprm_mm_init(struct linux_binprm *bprm)
 355{
 356        bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 357        return 0;
 358}
 359
 360static bool valid_arg_len(struct linux_binprm *bprm, long len)
 361{
 362        return len <= bprm->p;
 363}
 364
 365#endif /* CONFIG_MMU */
 366
 367/*
 368 * Create a new mm_struct and populate it with a temporary stack
 369 * vm_area_struct.  We don't have enough context at this point to set the stack
 370 * flags, permissions, and offset, so we use temporary values.  We'll update
 371 * them later in setup_arg_pages().
 372 */
 373static int bprm_mm_init(struct linux_binprm *bprm)
 374{
 375        int err;
 376        struct mm_struct *mm = NULL;
 377
 378        bprm->mm = mm = mm_alloc();
 379        err = -ENOMEM;
 380        if (!mm)
 381                goto err;
 382
 383        err = __bprm_mm_init(bprm);
 384        if (err)
 385                goto err;
 386
 387        return 0;
 388
 389err:
 390        if (mm) {
 391                bprm->mm = NULL;
 392                mmdrop(mm);
 393        }
 394
 395        return err;
 396}
 397
 398struct user_arg_ptr {
 399#ifdef CONFIG_COMPAT
 400        bool is_compat;
 401#endif
 402        union {
 403                const char __user *const __user *native;
 404#ifdef CONFIG_COMPAT
 405                const compat_uptr_t __user *compat;
 406#endif
 407        } ptr;
 408};
 409
 410static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 411{
 412        const char __user *native;
 413
 414#ifdef CONFIG_COMPAT
 415        if (unlikely(argv.is_compat)) {
 416                compat_uptr_t compat;
 417
 418                if (get_user(compat, argv.ptr.compat + nr))
 419                        return ERR_PTR(-EFAULT);
 420
 421                return compat_ptr(compat);
 422        }
 423#endif
 424
 425        if (get_user(native, argv.ptr.native + nr))
 426                return ERR_PTR(-EFAULT);
 427
 428        return native;
 429}
 430
 431/*
 432 * count() counts the number of strings in array ARGV.
 433 */
 434static int count(struct user_arg_ptr argv, int max)
 435{
 436        int i = 0;
 437
 438        if (argv.ptr.native != NULL) {
 439                for (;;) {
 440                        const char __user *p = get_user_arg_ptr(argv, i);
 441
 442                        if (!p)
 443                                break;
 444
 445                        if (IS_ERR(p))
 446                                return -EFAULT;
 447
 448                        if (i >= max)
 449                                return -E2BIG;
 450                        ++i;
 451
 452                        if (fatal_signal_pending(current))
 453                                return -ERESTARTNOHAND;
 454                        cond_resched();
 455                }
 456        }
 457        return i;
 458}
 459
 460/*
 461 * 'copy_strings()' copies argument/environment strings from the old
 462 * processes's memory to the new process's stack.  The call to get_user_pages()
 463 * ensures the destination page is created and not swapped out.
 464 */
 465static int copy_strings(int argc, struct user_arg_ptr argv,
 466                        struct linux_binprm *bprm)
 467{
 468        struct page *kmapped_page = NULL;
 469        char *kaddr = NULL;
 470        unsigned long kpos = 0;
 471        int ret;
 472
 473        while (argc-- > 0) {
 474                const char __user *str;
 475                int len;
 476                unsigned long pos;
 477
 478                ret = -EFAULT;
 479                str = get_user_arg_ptr(argv, argc);
 480                if (IS_ERR(str))
 481                        goto out;
 482
 483                len = strnlen_user(str, MAX_ARG_STRLEN);
 484                if (!len)
 485                        goto out;
 486
 487                ret = -E2BIG;
 488                if (!valid_arg_len(bprm, len))
 489                        goto out;
 490
 491                /* We're going to work our way backwords. */
 492                pos = bprm->p;
 493                str += len;
 494                bprm->p -= len;
 495
 496                while (len > 0) {
 497                        int offset, bytes_to_copy;
 498
 499                        if (fatal_signal_pending(current)) {
 500                                ret = -ERESTARTNOHAND;
 501                                goto out;
 502                        }
 503                        cond_resched();
 504
 505                        offset = pos % PAGE_SIZE;
 506                        if (offset == 0)
 507                                offset = PAGE_SIZE;
 508
 509                        bytes_to_copy = offset;
 510                        if (bytes_to_copy > len)
 511                                bytes_to_copy = len;
 512
 513                        offset -= bytes_to_copy;
 514                        pos -= bytes_to_copy;
 515                        str -= bytes_to_copy;
 516                        len -= bytes_to_copy;
 517
 518                        if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 519                                struct page *page;
 520
 521                                page = get_arg_page(bprm, pos, 1);
 522                                if (!page) {
 523                                        ret = -E2BIG;
 524                                        goto out;
 525                                }
 526
 527                                if (kmapped_page) {
 528                                        flush_kernel_dcache_page(kmapped_page);
 529                                        kunmap(kmapped_page);
 530                                        put_arg_page(kmapped_page);
 531                                }
 532                                kmapped_page = page;
 533                                kaddr = kmap(kmapped_page);
 534                                kpos = pos & PAGE_MASK;
 535                                flush_arg_page(bprm, kpos, kmapped_page);
 536                        }
 537                        if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 538                                ret = -EFAULT;
 539                                goto out;
 540                        }
 541                }
 542        }
 543        ret = 0;
 544out:
 545        if (kmapped_page) {
 546                flush_kernel_dcache_page(kmapped_page);
 547                kunmap(kmapped_page);
 548                put_arg_page(kmapped_page);
 549        }
 550        return ret;
 551}
 552
 553/*
 554 * Like copy_strings, but get argv and its values from kernel memory.
 555 */
 556int copy_strings_kernel(int argc, const char *const *__argv,
 557                        struct linux_binprm *bprm)
 558{
 559        int r;
 560        mm_segment_t oldfs = get_fs();
 561        struct user_arg_ptr argv = {
 562                .ptr.native = (const char __user *const  __user *)__argv,
 563        };
 564
 565        set_fs(KERNEL_DS);
 566        r = copy_strings(argc, argv, bprm);
 567        set_fs(oldfs);
 568
 569        return r;
 570}
 571EXPORT_SYMBOL(copy_strings_kernel);
 572
 573#ifdef CONFIG_MMU
 574
 575/*
 576 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 577 * the binfmt code determines where the new stack should reside, we shift it to
 578 * its final location.  The process proceeds as follows:
 579 *
 580 * 1) Use shift to calculate the new vma endpoints.
 581 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 582 *    arguments passed to subsequent functions are consistent.
 583 * 3) Move vma's page tables to the new range.
 584 * 4) Free up any cleared pgd range.
 585 * 5) Shrink the vma to cover only the new range.
 586 */
 587static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 588{
 589        struct mm_struct *mm = vma->vm_mm;
 590        unsigned long old_start = vma->vm_start;
 591        unsigned long old_end = vma->vm_end;
 592        unsigned long length = old_end - old_start;
 593        unsigned long new_start = old_start - shift;
 594        unsigned long new_end = old_end - shift;
 595        struct mmu_gather tlb;
 596
 597        BUG_ON(new_start > new_end);
 598
 599        /*
 600         * ensure there are no vmas between where we want to go
 601         * and where we are
 602         */
 603        if (vma != find_vma(mm, new_start))
 604                return -EFAULT;
 605
 606        /*
 607         * cover the whole range: [new_start, old_end)
 608         */
 609        if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 610                return -ENOMEM;
 611
 612        /*
 613         * move the page tables downwards, on failure we rely on
 614         * process cleanup to remove whatever mess we made.
 615         */
 616        if (length != move_page_tables(vma, old_start,
 617                                       vma, new_start, length, false))
 618                return -ENOMEM;
 619
 620        lru_add_drain();
 621        tlb_gather_mmu(&tlb, mm, old_start, old_end);
 622        if (new_end > old_start) {
 623                /*
 624                 * when the old and new regions overlap clear from new_end.
 625                 */
 626                free_pgd_range(&tlb, new_end, old_end, new_end,
 627                        vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 628        } else {
 629                /*
 630                 * otherwise, clean from old_start; this is done to not touch
 631                 * the address space in [new_end, old_start) some architectures
 632                 * have constraints on va-space that make this illegal (IA64) -
 633                 * for the others its just a little faster.
 634                 */
 635                free_pgd_range(&tlb, old_start, old_end, new_end,
 636                        vma->vm_next ? vma->vm_next->vm_start : USER_PGTABLES_CEILING);
 637        }
 638        tlb_finish_mmu(&tlb, old_start, old_end);
 639
 640        /*
 641         * Shrink the vma to just the new range.  Always succeeds.
 642         */
 643        vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 644
 645        return 0;
 646}
 647
 648/*
 649 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 650 * the stack is optionally relocated, and some extra space is added.
 651 */
 652int setup_arg_pages(struct linux_binprm *bprm,
 653                    unsigned long stack_top,
 654                    int executable_stack)
 655{
 656        unsigned long ret;
 657        unsigned long stack_shift;
 658        struct mm_struct *mm = current->mm;
 659        struct vm_area_struct *vma = bprm->vma;
 660        struct vm_area_struct *prev = NULL;
 661        unsigned long vm_flags;
 662        unsigned long stack_base;
 663        unsigned long stack_size;
 664        unsigned long stack_expand;
 665        unsigned long rlim_stack;
 666
 667#ifdef CONFIG_STACK_GROWSUP
 668        /* Limit stack size */
 669        stack_base = rlimit_max(RLIMIT_STACK);
 670        if (stack_base > STACK_SIZE_MAX)
 671                stack_base = STACK_SIZE_MAX;
 672
 673        /* Add space for stack randomization. */
 674        stack_base += (STACK_RND_MASK << PAGE_SHIFT);
 675
 676        /* Make sure we didn't let the argument array grow too large. */
 677        if (vma->vm_end - vma->vm_start > stack_base)
 678                return -ENOMEM;
 679
 680        stack_base = PAGE_ALIGN(stack_top - stack_base);
 681
 682        stack_shift = vma->vm_start - stack_base;
 683        mm->arg_start = bprm->p - stack_shift;
 684        bprm->p = vma->vm_end - stack_shift;
 685#else
 686        stack_top = arch_align_stack(stack_top);
 687        stack_top = PAGE_ALIGN(stack_top);
 688
 689        if (unlikely(stack_top < mmap_min_addr) ||
 690            unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 691                return -ENOMEM;
 692
 693        stack_shift = vma->vm_end - stack_top;
 694
 695        bprm->p -= stack_shift;
 696        mm->arg_start = bprm->p;
 697#endif
 698
 699        if (bprm->loader)
 700                bprm->loader -= stack_shift;
 701        bprm->exec -= stack_shift;
 702
 703        down_write(&mm->mmap_sem);
 704        vm_flags = VM_STACK_FLAGS;
 705
 706        /*
 707         * Adjust stack execute permissions; explicitly enable for
 708         * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 709         * (arch default) otherwise.
 710         */
 711        if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 712                vm_flags |= VM_EXEC;
 713        else if (executable_stack == EXSTACK_DISABLE_X)
 714                vm_flags &= ~VM_EXEC;
 715        vm_flags |= mm->def_flags;
 716        vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 717
 718        ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 719                        vm_flags);
 720        if (ret)
 721                goto out_unlock;
 722        BUG_ON(prev != vma);
 723
 724        /* Move stack pages down in memory. */
 725        if (stack_shift) {
 726                ret = shift_arg_pages(vma, stack_shift);
 727                if (ret)
 728                        goto out_unlock;
 729        }
 730
 731        /* mprotect_fixup is overkill to remove the temporary stack flags */
 732        vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 733
 734        stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 735        stack_size = vma->vm_end - vma->vm_start;
 736        /*
 737         * Align this down to a page boundary as expand_stack
 738         * will align it up.
 739         */
 740        rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 741#ifdef CONFIG_STACK_GROWSUP
 742        if (stack_size + stack_expand > rlim_stack)
 743                stack_base = vma->vm_start + rlim_stack;
 744        else
 745                stack_base = vma->vm_end + stack_expand;
 746#else
 747        if (stack_size + stack_expand > rlim_stack)
 748                stack_base = vma->vm_end - rlim_stack;
 749        else
 750                stack_base = vma->vm_start - stack_expand;
 751#endif
 752        current->mm->start_stack = bprm->p;
 753        ret = expand_stack(vma, stack_base);
 754        if (ret)
 755                ret = -EFAULT;
 756
 757out_unlock:
 758        up_write(&mm->mmap_sem);
 759        return ret;
 760}
 761EXPORT_SYMBOL(setup_arg_pages);
 762
 763#endif /* CONFIG_MMU */
 764
 765static struct file *do_open_execat(int fd, struct filename *name, int flags)
 766{
 767        struct file *file;
 768        int err;
 769        struct open_flags open_exec_flags = {
 770                .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 771                .acc_mode = MAY_EXEC,
 772                .intent = LOOKUP_OPEN,
 773                .lookup_flags = LOOKUP_FOLLOW,
 774        };
 775
 776        if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 777                return ERR_PTR(-EINVAL);
 778        if (flags & AT_SYMLINK_NOFOLLOW)
 779                open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
 780        if (flags & AT_EMPTY_PATH)
 781                open_exec_flags.lookup_flags |= LOOKUP_EMPTY;
 782
 783        file = do_filp_open(fd, name, &open_exec_flags);
 784        if (IS_ERR(file))
 785                goto out;
 786
 787        err = -EACCES;
 788        if (!S_ISREG(file_inode(file)->i_mode))
 789                goto exit;
 790
 791        if (path_noexec(&file->f_path))
 792                goto exit;
 793
 794        err = deny_write_access(file);
 795        if (err)
 796                goto exit;
 797
 798        if (name->name[0] != '\0')
 799                fsnotify_open(file);
 800
 801out:
 802        return file;
 803
 804exit:
 805        fput(file);
 806        return ERR_PTR(err);
 807}
 808
 809struct file *open_exec(const char *name)
 810{
 811        struct filename *filename = getname_kernel(name);
 812        struct file *f = ERR_CAST(filename);
 813
 814        if (!IS_ERR(filename)) {
 815                f = do_open_execat(AT_FDCWD, filename, 0);
 816                putname(filename);
 817        }
 818        return f;
 819}
 820EXPORT_SYMBOL(open_exec);
 821
 822int kernel_read(struct file *file, loff_t offset,
 823                char *addr, unsigned long count)
 824{
 825        mm_segment_t old_fs;
 826        loff_t pos = offset;
 827        int result;
 828
 829        old_fs = get_fs();
 830        set_fs(get_ds());
 831        /* The cast to a user pointer is valid due to the set_fs() */
 832        result = vfs_read(file, (void __user *)addr, count, &pos);
 833        set_fs(old_fs);
 834        return result;
 835}
 836
 837EXPORT_SYMBOL(kernel_read);
 838
 839int kernel_read_file(struct file *file, void **buf, loff_t *size,
 840                     loff_t max_size, enum kernel_read_file_id id)
 841{
 842        loff_t i_size, pos;
 843        ssize_t bytes = 0;
 844        int ret;
 845
 846        if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
 847                return -EINVAL;
 848
 849        ret = security_kernel_read_file(file, id);
 850        if (ret)
 851                return ret;
 852
 853        i_size = i_size_read(file_inode(file));
 854        if (max_size > 0 && i_size > max_size)
 855                return -EFBIG;
 856        if (i_size <= 0)
 857                return -EINVAL;
 858
 859        *buf = vmalloc(i_size);
 860        if (!*buf)
 861                return -ENOMEM;
 862
 863        pos = 0;
 864        while (pos < i_size) {
 865                bytes = kernel_read(file, pos, (char *)(*buf) + pos,
 866                                    i_size - pos);
 867                if (bytes < 0) {
 868                        ret = bytes;
 869                        goto out;
 870                }
 871
 872                if (bytes == 0)
 873                        break;
 874                pos += bytes;
 875        }
 876
 877        if (pos != i_size) {
 878                ret = -EIO;
 879                goto out;
 880        }
 881
 882        ret = security_kernel_post_read_file(file, *buf, i_size, id);
 883        if (!ret)
 884                *size = pos;
 885
 886out:
 887        if (ret < 0) {
 888                vfree(*buf);
 889                *buf = NULL;
 890        }
 891        return ret;
 892}
 893EXPORT_SYMBOL_GPL(kernel_read_file);
 894
 895int kernel_read_file_from_path(char *path, void **buf, loff_t *size,
 896                               loff_t max_size, enum kernel_read_file_id id)
 897{
 898        struct file *file;
 899        int ret;
 900
 901        if (!path || !*path)
 902                return -EINVAL;
 903
 904        file = filp_open(path, O_RDONLY, 0);
 905        if (IS_ERR(file))
 906                return PTR_ERR(file);
 907
 908        ret = kernel_read_file(file, buf, size, max_size, id);
 909        fput(file);
 910        return ret;
 911}
 912EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
 913
 914int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
 915                             enum kernel_read_file_id id)
 916{
 917        struct fd f = fdget(fd);
 918        int ret = -EBADF;
 919
 920        if (!f.file)
 921                goto out;
 922
 923        ret = kernel_read_file(f.file, buf, size, max_size, id);
 924out:
 925        fdput(f);
 926        return ret;
 927}
 928EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
 929
 930ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
 931{
 932        ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
 933        if (res > 0)
 934                flush_icache_range(addr, addr + len);
 935        return res;
 936}
 937EXPORT_SYMBOL(read_code);
 938
 939static int exec_mmap(struct mm_struct *mm)
 940{
 941        struct task_struct *tsk;
 942        struct mm_struct *old_mm, *active_mm;
 943
 944        /* Notify parent that we're no longer interested in the old VM */
 945        tsk = current;
 946        old_mm = current->mm;
 947        mm_release(tsk, old_mm);
 948
 949        if (old_mm) {
 950                sync_mm_rss(old_mm);
 951                /*
 952                 * Make sure that if there is a core dump in progress
 953                 * for the old mm, we get out and die instead of going
 954                 * through with the exec.  We must hold mmap_sem around
 955                 * checking core_state and changing tsk->mm.
 956                 */
 957                down_read(&old_mm->mmap_sem);
 958                if (unlikely(old_mm->core_state)) {
 959                        up_read(&old_mm->mmap_sem);
 960                        return -EINTR;
 961                }
 962        }
 963        task_lock(tsk);
 964        active_mm = tsk->active_mm;
 965        tsk->mm = mm;
 966        tsk->active_mm = mm;
 967        activate_mm(active_mm, mm);
 968        tsk->mm->vmacache_seqnum = 0;
 969        vmacache_flush(tsk);
 970        task_unlock(tsk);
 971        if (old_mm) {
 972                up_read(&old_mm->mmap_sem);
 973                BUG_ON(active_mm != old_mm);
 974                setmax_mm_hiwater_rss(&tsk->signal->maxrss, old_mm);
 975                mm_update_next_owner(old_mm);
 976                mmput(old_mm);
 977                return 0;
 978        }
 979        mmdrop(active_mm);
 980        return 0;
 981}
 982
 983/*
 984 * This function makes sure the current process has its own signal table,
 985 * so that flush_signal_handlers can later reset the handlers without
 986 * disturbing other processes.  (Other processes might share the signal
 987 * table via the CLONE_SIGHAND option to clone().)
 988 */
 989static int de_thread(struct task_struct *tsk)
 990{
 991        struct signal_struct *sig = tsk->signal;
 992        struct sighand_struct *oldsighand = tsk->sighand;
 993        spinlock_t *lock = &oldsighand->siglock;
 994
 995        if (thread_group_empty(tsk))
 996                goto no_thread_group;
 997
 998        /*
 999         * Kill all other threads in the thread group.
1000         */
1001        spin_lock_irq(lock);
1002        if (signal_group_exit(sig)) {
1003                /*
1004                 * Another group action in progress, just
1005                 * return so that the signal is processed.
1006                 */
1007                spin_unlock_irq(lock);
1008                return -EAGAIN;
1009        }
1010
1011        sig->group_exit_task = tsk;
1012        sig->notify_count = zap_other_threads(tsk);
1013        if (!thread_group_leader(tsk))
1014                sig->notify_count--;
1015
1016        while (sig->notify_count) {
1017                __set_current_state(TASK_KILLABLE);
1018                spin_unlock_irq(lock);
1019                schedule();
1020                if (unlikely(__fatal_signal_pending(tsk)))
1021                        goto killed;
1022                spin_lock_irq(lock);
1023        }
1024        spin_unlock_irq(lock);
1025
1026        /*
1027         * At this point all other threads have exited, all we have to
1028         * do is to wait for the thread group leader to become inactive,
1029         * and to assume its PID:
1030         */
1031        if (!thread_group_leader(tsk)) {
1032                struct task_struct *leader = tsk->group_leader;
1033
1034                for (;;) {
1035                        threadgroup_change_begin(tsk);
1036                        write_lock_irq(&tasklist_lock);
1037                        /*
1038                         * Do this under tasklist_lock to ensure that
1039                         * exit_notify() can't miss ->group_exit_task
1040                         */
1041                        sig->notify_count = -1;
1042                        if (likely(leader->exit_state))
1043                                break;
1044                        __set_current_state(TASK_KILLABLE);
1045                        write_unlock_irq(&tasklist_lock);
1046                        threadgroup_change_end(tsk);
1047                        schedule();
1048                        if (unlikely(__fatal_signal_pending(tsk)))
1049                                goto killed;
1050                }
1051
1052                /*
1053                 * The only record we have of the real-time age of a
1054                 * process, regardless of execs it's done, is start_time.
1055                 * All the past CPU time is accumulated in signal_struct
1056                 * from sister threads now dead.  But in this non-leader
1057                 * exec, nothing survives from the original leader thread,
1058                 * whose birth marks the true age of this process now.
1059                 * When we take on its identity by switching to its PID, we
1060                 * also take its birthdate (always earlier than our own).
1061                 */
1062                tsk->start_time = leader->start_time;
1063                tsk->real_start_time = leader->real_start_time;
1064
1065                BUG_ON(!same_thread_group(leader, tsk));
1066                BUG_ON(has_group_leader_pid(tsk));
1067                /*
1068                 * An exec() starts a new thread group with the
1069                 * TGID of the previous thread group. Rehash the
1070                 * two threads with a switched PID, and release
1071                 * the former thread group leader:
1072                 */
1073
1074                /* Become a process group leader with the old leader's pid.
1075                 * The old leader becomes a thread of the this thread group.
1076                 * Note: The old leader also uses this pid until release_task
1077                 *       is called.  Odd but simple and correct.
1078                 */
1079                tsk->pid = leader->pid;
1080                change_pid(tsk, PIDTYPE_PID, task_pid(leader));
1081                transfer_pid(leader, tsk, PIDTYPE_PGID);
1082                transfer_pid(leader, tsk, PIDTYPE_SID);
1083
1084                list_replace_rcu(&leader->tasks, &tsk->tasks);
1085                list_replace_init(&leader->sibling, &tsk->sibling);
1086
1087                tsk->group_leader = tsk;
1088                leader->group_leader = tsk;
1089
1090                tsk->exit_signal = SIGCHLD;
1091                leader->exit_signal = -1;
1092
1093                BUG_ON(leader->exit_state != EXIT_ZOMBIE);
1094                leader->exit_state = EXIT_DEAD;
1095
1096                /*
1097                 * We are going to release_task()->ptrace_unlink() silently,
1098                 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
1099                 * the tracer wont't block again waiting for this thread.
1100                 */
1101                if (unlikely(leader->ptrace))
1102                        __wake_up_parent(leader, leader->parent);
1103                write_unlock_irq(&tasklist_lock);
1104                threadgroup_change_end(tsk);
1105
1106                release_task(leader);
1107        }
1108
1109        sig->group_exit_task = NULL;
1110        sig->notify_count = 0;
1111
1112no_thread_group:
1113        /* we have changed execution domain */
1114        tsk->exit_signal = SIGCHLD;
1115
1116        exit_itimers(sig);
1117        flush_itimer_signals();
1118
1119        if (atomic_read(&oldsighand->count) != 1) {
1120                struct sighand_struct *newsighand;
1121                /*
1122                 * This ->sighand is shared with the CLONE_SIGHAND
1123                 * but not CLONE_THREAD task, switch to the new one.
1124                 */
1125                newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1126                if (!newsighand)
1127                        return -ENOMEM;
1128
1129                atomic_set(&newsighand->count, 1);
1130                memcpy(newsighand->action, oldsighand->action,
1131                       sizeof(newsighand->action));
1132
1133                write_lock_irq(&tasklist_lock);
1134                spin_lock(&oldsighand->siglock);
1135                rcu_assign_pointer(tsk->sighand, newsighand);
1136                spin_unlock(&oldsighand->siglock);
1137                write_unlock_irq(&tasklist_lock);
1138
1139                __cleanup_sighand(oldsighand);
1140        }
1141
1142        BUG_ON(!thread_group_leader(tsk));
1143        return 0;
1144
1145killed:
1146        /* protects against exit_notify() and __exit_signal() */
1147        read_lock(&tasklist_lock);
1148        sig->group_exit_task = NULL;
1149        sig->notify_count = 0;
1150        read_unlock(&tasklist_lock);
1151        return -EAGAIN;
1152}
1153
1154char *get_task_comm(char *buf, struct task_struct *tsk)
1155{
1156        /* buf must be at least sizeof(tsk->comm) in size */
1157        task_lock(tsk);
1158        strncpy(buf, tsk->comm, sizeof(tsk->comm));
1159        task_unlock(tsk);
1160        return buf;
1161}
1162EXPORT_SYMBOL_GPL(get_task_comm);
1163
1164/*
1165 * These functions flushes out all traces of the currently running executable
1166 * so that a new one can be started
1167 */
1168
1169void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
1170{
1171        task_lock(tsk);
1172        trace_task_rename(tsk, buf);
1173        strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1174        task_unlock(tsk);
1175        perf_event_comm(tsk, exec);
1176}
1177
1178int flush_old_exec(struct linux_binprm * bprm)
1179{
1180        int retval;
1181
1182        /*
1183         * Make sure we have a private signal table and that
1184         * we are unassociated from the previous thread group.
1185         */
1186        retval = de_thread(current);
1187        if (retval)
1188                goto out;
1189
1190        /*
1191         * Must be called _before_ exec_mmap() as bprm->mm is
1192         * not visibile until then. This also enables the update
1193         * to be lockless.
1194         */
1195        set_mm_exe_file(bprm->mm, bprm->file);
1196
1197        /*
1198         * Release all of the old mmap stuff
1199         */
1200        acct_arg_size(bprm, 0);
1201        retval = exec_mmap(bprm->mm);
1202        if (retval)
1203                goto out;
1204
1205        bprm->mm = NULL;                /* We're using it now */
1206
1207        set_fs(USER_DS);
1208        current->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
1209                                        PF_NOFREEZE | PF_NO_SETAFFINITY);
1210        flush_thread();
1211        current->personality &= ~bprm->per_clear;
1212
1213        return 0;
1214
1215out:
1216        return retval;
1217}
1218EXPORT_SYMBOL(flush_old_exec);
1219
1220void would_dump(struct linux_binprm *bprm, struct file *file)
1221{
1222        if (inode_permission(file_inode(file), MAY_READ) < 0)
1223                bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
1224}
1225EXPORT_SYMBOL(would_dump);
1226
1227void setup_new_exec(struct linux_binprm * bprm)
1228{
1229        arch_pick_mmap_layout(current->mm);
1230
1231        /* This is the point of no return */
1232        current->sas_ss_sp = current->sas_ss_size = 0;
1233
1234        if (uid_eq(current_euid(), current_uid()) && gid_eq(current_egid(), current_gid()))
1235                set_dumpable(current->mm, SUID_DUMP_USER);
1236        else
1237                set_dumpable(current->mm, suid_dumpable);
1238
1239        perf_event_exec();
1240        __set_task_comm(current, kbasename(bprm->filename), true);
1241
1242        /* Set the new mm task size. We have to do that late because it may
1243         * depend on TIF_32BIT which is only updated in flush_thread() on
1244         * some architectures like powerpc
1245         */
1246        current->mm->task_size = TASK_SIZE;
1247
1248        /* install the new credentials */
1249        if (!uid_eq(bprm->cred->uid, current_euid()) ||
1250            !gid_eq(bprm->cred->gid, current_egid())) {
1251                current->pdeath_signal = 0;
1252        } else {
1253                would_dump(bprm, bprm->file);
1254                if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)
1255                        set_dumpable(current->mm, suid_dumpable);
1256        }
1257
1258        /* An exec changes our domain. We are no longer part of the thread
1259           group */
1260        current->self_exec_id++;
1261        flush_signal_handlers(current, 0);
1262        do_close_on_exec(current->files);
1263}
1264EXPORT_SYMBOL(setup_new_exec);
1265
1266/*
1267 * Prepare credentials and lock ->cred_guard_mutex.
1268 * install_exec_creds() commits the new creds and drops the lock.
1269 * Or, if exec fails before, free_bprm() should release ->cred and
1270 * and unlock.
1271 */
1272int prepare_bprm_creds(struct linux_binprm *bprm)
1273{
1274        if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1275                return -ERESTARTNOINTR;
1276
1277        bprm->cred = prepare_exec_creds();
1278        if (likely(bprm->cred))
1279                return 0;
1280
1281        mutex_unlock(&current->signal->cred_guard_mutex);
1282        return -ENOMEM;
1283}
1284
1285static void free_bprm(struct linux_binprm *bprm)
1286{
1287        free_arg_pages(bprm);
1288        if (bprm->cred) {
1289                mutex_unlock(&current->signal->cred_guard_mutex);
1290                abort_creds(bprm->cred);
1291        }
1292        if (bprm->file) {
1293                allow_write_access(bprm->file);
1294                fput(bprm->file);
1295        }
1296        /* If a binfmt changed the interp, free it. */
1297        if (bprm->interp != bprm->filename)
1298                kfree(bprm->interp);
1299        kfree(bprm);
1300}
1301
1302int bprm_change_interp(char *interp, struct linux_binprm *bprm)
1303{
1304        /* If a binfmt changed the interp, free it first. */
1305        if (bprm->interp != bprm->filename)
1306                kfree(bprm->interp);
1307        bprm->interp = kstrdup(interp, GFP_KERNEL);
1308        if (!bprm->interp)
1309                return -ENOMEM;
1310        return 0;
1311}
1312EXPORT_SYMBOL(bprm_change_interp);
1313
1314/*
1315 * install the new credentials for this executable
1316 */
1317void install_exec_creds(struct linux_binprm *bprm)
1318{
1319        security_bprm_committing_creds(bprm);
1320
1321        commit_creds(bprm->cred);
1322        bprm->cred = NULL;
1323
1324        /*
1325         * Disable monitoring for regular users
1326         * when executing setuid binaries. Must
1327         * wait until new credentials are committed
1328         * by commit_creds() above
1329         */
1330        if (get_dumpable(current->mm) != SUID_DUMP_USER)
1331                perf_event_exit_task(current);
1332        /*
1333         * cred_guard_mutex must be held at least to this point to prevent
1334         * ptrace_attach() from altering our determination of the task's
1335         * credentials; any time after this it may be unlocked.
1336         */
1337        security_bprm_committed_creds(bprm);
1338        mutex_unlock(&current->signal->cred_guard_mutex);
1339}
1340EXPORT_SYMBOL(install_exec_creds);
1341
1342/*
1343 * determine how safe it is to execute the proposed program
1344 * - the caller must hold ->cred_guard_mutex to protect against
1345 *   PTRACE_ATTACH or seccomp thread-sync
1346 */
1347static void check_unsafe_exec(struct linux_binprm *bprm)
1348{
1349        struct task_struct *p = current, *t;
1350        unsigned n_fs;
1351
1352        if (p->ptrace) {
1353                if (p->ptrace & PT_PTRACE_CAP)
1354                        bprm->unsafe |= LSM_UNSAFE_PTRACE_CAP;
1355                else
1356                        bprm->unsafe |= LSM_UNSAFE_PTRACE;
1357        }
1358
1359        /*
1360         * This isn't strictly necessary, but it makes it harder for LSMs to
1361         * mess up.
1362         */
1363        if (task_no_new_privs(current))
1364                bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
1365
1366        t = p;
1367        n_fs = 1;
1368        spin_lock(&p->fs->lock);
1369        rcu_read_lock();
1370        while_each_thread(p, t) {
1371                if (t->fs == p->fs)
1372                        n_fs++;
1373        }
1374        rcu_read_unlock();
1375
1376        if (p->fs->users > n_fs)
1377                bprm->unsafe |= LSM_UNSAFE_SHARE;
1378        else
1379                p->fs->in_exec = 1;
1380        spin_unlock(&p->fs->lock);
1381}
1382
1383static void bprm_fill_uid(struct linux_binprm *bprm)
1384{
1385        struct inode *inode;
1386        unsigned int mode;
1387        kuid_t uid;
1388        kgid_t gid;
1389
1390        /* clear any previous set[ug]id data from a previous binary */
1391        bprm->cred->euid = current_euid();
1392        bprm->cred->egid = current_egid();
1393
1394        if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
1395                return;
1396
1397        if (task_no_new_privs(current))
1398                return;
1399
1400        inode = file_inode(bprm->file);
1401        mode = READ_ONCE(inode->i_mode);
1402        if (!(mode & (S_ISUID|S_ISGID)))
1403                return;
1404
1405        /* Be careful if suid/sgid is set */
1406        inode_lock(inode);
1407
1408        /* reload atomically mode/uid/gid now that lock held */
1409        mode = inode->i_mode;
1410        uid = inode->i_uid;
1411        gid = inode->i_gid;
1412        inode_unlock(inode);
1413
1414        /* We ignore suid/sgid if there are no mappings for them in the ns */
1415        if (!kuid_has_mapping(bprm->cred->user_ns, uid) ||
1416                 !kgid_has_mapping(bprm->cred->user_ns, gid))
1417                return;
1418
1419        if (mode & S_ISUID) {
1420                bprm->per_clear |= PER_CLEAR_ON_SETID;
1421                bprm->cred->euid = uid;
1422        }
1423
1424        if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1425                bprm->per_clear |= PER_CLEAR_ON_SETID;
1426                bprm->cred->egid = gid;
1427        }
1428}
1429
1430/*
1431 * Fill the binprm structure from the inode.
1432 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1433 *
1434 * This may be called multiple times for binary chains (scripts for example).
1435 */
1436int prepare_binprm(struct linux_binprm *bprm)
1437{
1438        int retval;
1439
1440        bprm_fill_uid(bprm);
1441
1442        /* fill in binprm security blob */
1443        retval = security_bprm_set_creds(bprm);
1444        if (retval)
1445                return retval;
1446        bprm->cred_prepared = 1;
1447
1448        memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1449        return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1450}
1451
1452EXPORT_SYMBOL(prepare_binprm);
1453
1454/*
1455 * Arguments are '\0' separated strings found at the location bprm->p
1456 * points to; chop off the first by relocating brpm->p to right after
1457 * the first '\0' encountered.
1458 */
1459int remove_arg_zero(struct linux_binprm *bprm)
1460{
1461        int ret = 0;
1462        unsigned long offset;
1463        char *kaddr;
1464        struct page *page;
1465
1466        if (!bprm->argc)
1467                return 0;
1468
1469        do {
1470                offset = bprm->p & ~PAGE_MASK;
1471                page = get_arg_page(bprm, bprm->p, 0);
1472                if (!page) {
1473                        ret = -EFAULT;
1474                        goto out;
1475                }
1476                kaddr = kmap_atomic(page);
1477
1478                for (; offset < PAGE_SIZE && kaddr[offset];
1479                                offset++, bprm->p++)
1480                        ;
1481
1482                kunmap_atomic(kaddr);
1483                put_arg_page(page);
1484
1485                if (offset == PAGE_SIZE)
1486                        free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1487        } while (offset == PAGE_SIZE);
1488
1489        bprm->p++;
1490        bprm->argc--;
1491        ret = 0;
1492
1493out:
1494        return ret;
1495}
1496EXPORT_SYMBOL(remove_arg_zero);
1497
1498#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1499/*
1500 * cycle the list of binary formats handler, until one recognizes the image
1501 */
1502int search_binary_handler(struct linux_binprm *bprm)
1503{
1504        bool need_retry = IS_ENABLED(CONFIG_MODULES);
1505        struct linux_binfmt *fmt;
1506        int retval;
1507
1508        /* This allows 4 levels of binfmt rewrites before failing hard. */
1509        if (bprm->recursion_depth > 5)
1510                return -ELOOP;
1511
1512        retval = security_bprm_check(bprm);
1513        if (retval)
1514                return retval;
1515
1516        retval = -ENOENT;
1517 retry:
1518        read_lock(&binfmt_lock);
1519        list_for_each_entry(fmt, &formats, lh) {
1520                if (!try_module_get(fmt->module))
1521                        continue;
1522                read_unlock(&binfmt_lock);
1523                bprm->recursion_depth++;
1524                retval = fmt->load_binary(bprm);
1525                read_lock(&binfmt_lock);
1526                put_binfmt(fmt);
1527                bprm->recursion_depth--;
1528                if (retval < 0 && !bprm->mm) {
1529                        /* we got to flush_old_exec() and failed after it */
1530                        read_unlock(&binfmt_lock);
1531                        force_sigsegv(SIGSEGV, current);
1532                        return retval;
1533                }
1534                if (retval != -ENOEXEC || !bprm->file) {
1535                        read_unlock(&binfmt_lock);
1536                        return retval;
1537                }
1538        }
1539        read_unlock(&binfmt_lock);
1540
1541        if (need_retry) {
1542                if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
1543                    printable(bprm->buf[2]) && printable(bprm->buf[3]))
1544                        return retval;
1545                if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
1546                        return retval;
1547                need_retry = false;
1548                goto retry;
1549        }
1550
1551        return retval;
1552}
1553EXPORT_SYMBOL(search_binary_handler);
1554
1555static int exec_binprm(struct linux_binprm *bprm)
1556{
1557        pid_t old_pid, old_vpid;
1558        int ret;
1559
1560        /* Need to fetch pid before load_binary changes it */
1561        old_pid = current->pid;
1562        rcu_read_lock();
1563        old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
1564        rcu_read_unlock();
1565
1566        ret = search_binary_handler(bprm);
1567        if (ret >= 0) {
1568                audit_bprm(bprm);
1569                trace_sched_process_exec(current, old_pid, bprm);
1570                ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
1571                proc_exec_connector(current);
1572        }
1573
1574        return ret;
1575}
1576
1577/*
1578 * sys_execve() executes a new program.
1579 */
1580static int do_execveat_common(int fd, struct filename *filename,
1581                              struct user_arg_ptr argv,
1582                              struct user_arg_ptr envp,
1583                              int flags)
1584{
1585        char *pathbuf = NULL;
1586        struct linux_binprm *bprm;
1587        struct file *file;
1588        struct files_struct *displaced;
1589        int retval;
1590
1591        if (IS_ERR(filename))
1592                return PTR_ERR(filename);
1593
1594        /*
1595         * We move the actual failure in case of RLIMIT_NPROC excess from
1596         * set*uid() to execve() because too many poorly written programs
1597         * don't check setuid() return code.  Here we additionally recheck
1598         * whether NPROC limit is still exceeded.
1599         */
1600        if ((current->flags & PF_NPROC_EXCEEDED) &&
1601            atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1602                retval = -EAGAIN;
1603                goto out_ret;
1604        }
1605
1606        /* We're below the limit (still or again), so we don't want to make
1607         * further execve() calls fail. */
1608        current->flags &= ~PF_NPROC_EXCEEDED;
1609
1610        retval = unshare_files(&displaced);
1611        if (retval)
1612                goto out_ret;
1613
1614        retval = -ENOMEM;
1615        bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1616        if (!bprm)
1617                goto out_files;
1618
1619        retval = prepare_bprm_creds(bprm);
1620        if (retval)
1621                goto out_free;
1622
1623        check_unsafe_exec(bprm);
1624        current->in_execve = 1;
1625
1626        file = do_open_execat(fd, filename, flags);
1627        retval = PTR_ERR(file);
1628        if (IS_ERR(file))
1629                goto out_unmark;
1630
1631        sched_exec();
1632
1633        bprm->file = file;
1634        if (fd == AT_FDCWD || filename->name[0] == '/') {
1635                bprm->filename = filename->name;
1636        } else {
1637                if (filename->name[0] == '\0')
1638                        pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d", fd);
1639                else
1640                        pathbuf = kasprintf(GFP_TEMPORARY, "/dev/fd/%d/%s",
1641                                            fd, filename->name);
1642                if (!pathbuf) {
1643                        retval = -ENOMEM;
1644                        goto out_unmark;
1645                }
1646                /*
1647                 * Record that a name derived from an O_CLOEXEC fd will be
1648                 * inaccessible after exec. Relies on having exclusive access to
1649                 * current->files (due to unshare_files above).
1650                 */
1651                if (close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
1652                        bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
1653                bprm->filename = pathbuf;
1654        }
1655        bprm->interp = bprm->filename;
1656
1657        retval = bprm_mm_init(bprm);
1658        if (retval)
1659                goto out_unmark;
1660
1661        bprm->argc = count(argv, MAX_ARG_STRINGS);
1662        if ((retval = bprm->argc) < 0)
1663                goto out;
1664
1665        bprm->envc = count(envp, MAX_ARG_STRINGS);
1666        if ((retval = bprm->envc) < 0)
1667                goto out;
1668
1669        retval = prepare_binprm(bprm);
1670        if (retval < 0)
1671                goto out;
1672
1673        retval = copy_strings_kernel(1, &bprm->filename, bprm);
1674        if (retval < 0)
1675                goto out;
1676
1677        bprm->exec = bprm->p;
1678        retval = copy_strings(bprm->envc, envp, bprm);
1679        if (retval < 0)
1680                goto out;
1681
1682        retval = copy_strings(bprm->argc, argv, bprm);
1683        if (retval < 0)
1684                goto out;
1685
1686        retval = exec_binprm(bprm);
1687        if (retval < 0)
1688                goto out;
1689
1690        /* execve succeeded */
1691        current->fs->in_exec = 0;
1692        current->in_execve = 0;
1693        acct_update_integrals(current);
1694        task_numa_free(current);
1695        free_bprm(bprm);
1696        kfree(pathbuf);
1697        putname(filename);
1698        if (displaced)
1699                put_files_struct(displaced);
1700        return retval;
1701
1702out:
1703        if (bprm->mm) {
1704                acct_arg_size(bprm, 0);
1705                mmput(bprm->mm);
1706        }
1707
1708out_unmark:
1709        current->fs->in_exec = 0;
1710        current->in_execve = 0;
1711
1712out_free:
1713        free_bprm(bprm);
1714        kfree(pathbuf);
1715
1716out_files:
1717        if (displaced)
1718                reset_files_struct(displaced);
1719out_ret:
1720        putname(filename);
1721        return retval;
1722}
1723
1724int do_execve(struct filename *filename,
1725        const char __user *const __user *__argv,
1726        const char __user *const __user *__envp)
1727{
1728        struct user_arg_ptr argv = { .ptr.native = __argv };
1729        struct user_arg_ptr envp = { .ptr.native = __envp };
1730        return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1731}
1732
1733int do_execveat(int fd, struct filename *filename,
1734                const char __user *const __user *__argv,
1735                const char __user *const __user *__envp,
1736                int flags)
1737{
1738        struct user_arg_ptr argv = { .ptr.native = __argv };
1739        struct user_arg_ptr envp = { .ptr.native = __envp };
1740
1741        return do_execveat_common(fd, filename, argv, envp, flags);
1742}
1743
1744#ifdef CONFIG_COMPAT
1745static int compat_do_execve(struct filename *filename,
1746        const compat_uptr_t __user *__argv,
1747        const compat_uptr_t __user *__envp)
1748{
1749        struct user_arg_ptr argv = {
1750                .is_compat = true,
1751                .ptr.compat = __argv,
1752        };
1753        struct user_arg_ptr envp = {
1754                .is_compat = true,
1755                .ptr.compat = __envp,
1756        };
1757        return do_execveat_common(AT_FDCWD, filename, argv, envp, 0);
1758}
1759
1760static int compat_do_execveat(int fd, struct filename *filename,
1761                              const compat_uptr_t __user *__argv,
1762                              const compat_uptr_t __user *__envp,
1763                              int flags)
1764{
1765        struct user_arg_ptr argv = {
1766                .is_compat = true,
1767                .ptr.compat = __argv,
1768        };
1769        struct user_arg_ptr envp = {
1770                .is_compat = true,
1771                .ptr.compat = __envp,
1772        };
1773        return do_execveat_common(fd, filename, argv, envp, flags);
1774}
1775#endif
1776
1777void set_binfmt(struct linux_binfmt *new)
1778{
1779        struct mm_struct *mm = current->mm;
1780
1781        if (mm->binfmt)
1782                module_put(mm->binfmt->module);
1783
1784        mm->binfmt = new;
1785        if (new)
1786                __module_get(new->module);
1787}
1788EXPORT_SYMBOL(set_binfmt);
1789
1790/*
1791 * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
1792 */
1793void set_dumpable(struct mm_struct *mm, int value)
1794{
1795        unsigned long old, new;
1796
1797        if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
1798                return;
1799
1800        do {
1801                old = ACCESS_ONCE(mm->flags);
1802                new = (old & ~MMF_DUMPABLE_MASK) | value;
1803        } while (cmpxchg(&mm->flags, old, new) != old);
1804}
1805
1806SYSCALL_DEFINE3(execve,
1807                const char __user *, filename,
1808                const char __user *const __user *, argv,
1809                const char __user *const __user *, envp)
1810{
1811        return do_execve(getname(filename), argv, envp);
1812}
1813
1814SYSCALL_DEFINE5(execveat,
1815                int, fd, const char __user *, filename,
1816                const char __user *const __user *, argv,
1817                const char __user *const __user *, envp,
1818                int, flags)
1819{
1820        int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1821
1822        return do_execveat(fd,
1823                           getname_flags(filename, lookup_flags, NULL),
1824                           argv, envp, flags);
1825}
1826
1827#ifdef CONFIG_COMPAT
1828COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
1829        const compat_uptr_t __user *, argv,
1830        const compat_uptr_t __user *, envp)
1831{
1832        return compat_do_execve(getname(filename), argv, envp);
1833}
1834
1835COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
1836                       const char __user *, filename,
1837                       const compat_uptr_t __user *, argv,
1838                       const compat_uptr_t __user *, envp,
1839                       int,  flags)
1840{
1841        int lookup_flags = (flags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
1842
1843        return compat_do_execveat(fd,
1844                                  getname_flags(filename, lookup_flags, NULL),
1845                                  argv, envp, flags);
1846}
1847#endif
1848
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