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/smp_lock.h>
  32#include <linux/swap.h>
  33#include <linux/string.h>
  34#include <linux/init.h>
  35#include <linux/pagemap.h>
  36#include <linux/highmem.h>
  37#include <linux/spinlock.h>
  38#include <linux/key.h>
  39#include <linux/personality.h>
  40#include <linux/binfmts.h>
  41#include <linux/utsname.h>
  42#include <linux/pid_namespace.h>
  43#include <linux/module.h>
  44#include <linux/namei.h>
  45#include <linux/proc_fs.h>
  46#include <linux/mount.h>
  47#include <linux/security.h>
  48#include <linux/syscalls.h>
  49#include <linux/tsacct_kern.h>
  50#include <linux/cn_proc.h>
  51#include <linux/audit.h>
  52#include <linux/tracehook.h>
  53#include <linux/kmod.h>
  54
  55#include <asm/uaccess.h>
  56#include <asm/mmu_context.h>
  57#include <asm/tlb.h>
  58
  59#ifdef __alpha__
  60/* for /sbin/loader handling in search_binary_handler() */
  61#include <linux/a.out.h>
  62#endif
  63
  64int core_uses_pid;
  65char core_pattern[CORENAME_MAX_SIZE] = "core";
  66int suid_dumpable = 0;
  67
  68/* The maximal length of core_pattern is also specified in sysctl.c */
  69
  70static LIST_HEAD(formats);
  71static DEFINE_RWLOCK(binfmt_lock);
  72
  73int register_binfmt(struct linux_binfmt * fmt)
  74{
  75        if (!fmt)
  76                return -EINVAL;
  77        write_lock(&binfmt_lock);
  78        list_add(&fmt->lh, &formats);
  79        write_unlock(&binfmt_lock);
  80        return 0;       
  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 nameidata nd;
 109        char *tmp = getname(library);
 110        int error = PTR_ERR(tmp);
 111
 112        if (!IS_ERR(tmp)) {
 113                error = path_lookup_open(AT_FDCWD, tmp,
 114                                         LOOKUP_FOLLOW, &nd,
 115                                         FMODE_READ|FMODE_EXEC);
 116                putname(tmp);
 117        }
 118        if (error)
 119                goto out;
 120
 121        error = -EINVAL;
 122        if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 123                goto exit;
 124
 125        error = -EACCES;
 126        if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
 127                goto exit;
 128
 129        error = vfs_permission(&nd, MAY_READ | MAY_EXEC | MAY_OPEN);
 130        if (error)
 131                goto exit;
 132
 133        file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 134        error = PTR_ERR(file);
 135        if (IS_ERR(file))
 136                goto out;
 137
 138        error = -ENOEXEC;
 139        if(file->f_op) {
 140                struct linux_binfmt * fmt;
 141
 142                read_lock(&binfmt_lock);
 143                list_for_each_entry(fmt, &formats, lh) {
 144                        if (!fmt->load_shlib)
 145                                continue;
 146                        if (!try_module_get(fmt->module))
 147                                continue;
 148                        read_unlock(&binfmt_lock);
 149                        error = fmt->load_shlib(file);
 150                        read_lock(&binfmt_lock);
 151                        put_binfmt(fmt);
 152                        if (error != -ENOEXEC)
 153                                break;
 154                }
 155                read_unlock(&binfmt_lock);
 156        }
 157        fput(file);
 158out:
 159        return error;
 160exit:
 161        release_open_intent(&nd);
 162        path_put(&nd.path);
 163        goto out;
 164}
 165
 166#ifdef CONFIG_MMU
 167
 168static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 169                int write)
 170{
 171        struct page *page;
 172        int ret;
 173
 174#ifdef CONFIG_STACK_GROWSUP
 175        if (write) {
 176                ret = expand_stack_downwards(bprm->vma, pos);
 177                if (ret < 0)
 178                        return NULL;
 179        }
 180#endif
 181        ret = get_user_pages(current, bprm->mm, pos,
 182                        1, write, 1, &page, NULL);
 183        if (ret <= 0)
 184                return NULL;
 185
 186        if (write) {
 187                unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 188                struct rlimit *rlim;
 189
 190                /*
 191                 * We've historically supported up to 32 pages (ARG_MAX)
 192                 * of argument strings even with small stacks
 193                 */
 194                if (size <= ARG_MAX)
 195                        return page;
 196
 197                /*
 198                 * Limit to 1/4-th the stack size for the argv+env strings.
 199                 * This ensures that:
 200                 *  - the remaining binfmt code will not run out of stack space,
 201                 *  - the program will have a reasonable amount of stack left
 202                 *    to work from.
 203                 */
 204                rlim = current->signal->rlim;
 205                if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
 206                        put_page(page);
 207                        return NULL;
 208                }
 209        }
 210
 211        return page;
 212}
 213
 214static void put_arg_page(struct page *page)
 215{
 216        put_page(page);
 217}
 218
 219static void free_arg_page(struct linux_binprm *bprm, int i)
 220{
 221}
 222
 223static void free_arg_pages(struct linux_binprm *bprm)
 224{
 225}
 226
 227static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 228                struct page *page)
 229{
 230        flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 231}
 232
 233static int __bprm_mm_init(struct linux_binprm *bprm)
 234{
 235        int err = -ENOMEM;
 236        struct vm_area_struct *vma = NULL;
 237        struct mm_struct *mm = bprm->mm;
 238
 239        bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 240        if (!vma)
 241                goto err;
 242
 243        down_write(&mm->mmap_sem);
 244        vma->vm_mm = mm;
 245
 246        /*
 247         * Place the stack at the largest stack address the architecture
 248         * supports. Later, we'll move this to an appropriate place. We don't
 249         * use STACK_TOP because that can depend on attributes which aren't
 250         * configured yet.
 251         */
 252        vma->vm_end = STACK_TOP_MAX;
 253        vma->vm_start = vma->vm_end - PAGE_SIZE;
 254
 255        vma->vm_flags = VM_STACK_FLAGS;
 256        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 257        err = insert_vm_struct(mm, vma);
 258        if (err) {
 259                up_write(&mm->mmap_sem);
 260                goto err;
 261        }
 262
 263        mm->stack_vm = mm->total_vm = 1;
 264        up_write(&mm->mmap_sem);
 265
 266        bprm->p = vma->vm_end - sizeof(void *);
 267
 268        return 0;
 269
 270err:
 271        if (vma) {
 272                bprm->vma = NULL;
 273                kmem_cache_free(vm_area_cachep, vma);
 274        }
 275
 276        return err;
 277}
 278
 279static bool valid_arg_len(struct linux_binprm *bprm, long len)
 280{
 281        return len <= MAX_ARG_STRLEN;
 282}
 283
 284#else
 285
 286static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 287                int write)
 288{
 289        struct page *page;
 290
 291        page = bprm->page[pos / PAGE_SIZE];
 292        if (!page && write) {
 293                page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 294                if (!page)
 295                        return NULL;
 296                bprm->page[pos / PAGE_SIZE] = page;
 297        }
 298
 299        return page;
 300}
 301
 302static void put_arg_page(struct page *page)
 303{
 304}
 305
 306static void free_arg_page(struct linux_binprm *bprm, int i)
 307{
 308        if (bprm->page[i]) {
 309                __free_page(bprm->page[i]);
 310                bprm->page[i] = NULL;
 311        }
 312}
 313
 314static void free_arg_pages(struct linux_binprm *bprm)
 315{
 316        int i;
 317
 318        for (i = 0; i < MAX_ARG_PAGES; i++)
 319                free_arg_page(bprm, i);
 320}
 321
 322static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 323                struct page *page)
 324{
 325}
 326
 327static int __bprm_mm_init(struct linux_binprm *bprm)
 328{
 329        bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 330        return 0;
 331}
 332
 333static bool valid_arg_len(struct linux_binprm *bprm, long len)
 334{
 335        return len <= bprm->p;
 336}
 337
 338#endif /* CONFIG_MMU */
 339
 340/*
 341 * Create a new mm_struct and populate it with a temporary stack
 342 * vm_area_struct.  We don't have enough context at this point to set the stack
 343 * flags, permissions, and offset, so we use temporary values.  We'll update
 344 * them later in setup_arg_pages().
 345 */
 346int bprm_mm_init(struct linux_binprm *bprm)
 347{
 348        int err;
 349        struct mm_struct *mm = NULL;
 350
 351        bprm->mm = mm = mm_alloc();
 352        err = -ENOMEM;
 353        if (!mm)
 354                goto err;
 355
 356        err = init_new_context(current, mm);
 357        if (err)
 358                goto err;
 359
 360        err = __bprm_mm_init(bprm);
 361        if (err)
 362                goto err;
 363
 364        return 0;
 365
 366err:
 367        if (mm) {
 368                bprm->mm = NULL;
 369                mmdrop(mm);
 370        }
 371
 372        return err;
 373}
 374
 375/*
 376 * count() counts the number of strings in array ARGV.
 377 */
 378static int count(char __user * __user * argv, int max)
 379{
 380        int i = 0;
 381
 382        if (argv != NULL) {
 383                for (;;) {
 384                        char __user * p;
 385
 386                        if (get_user(p, argv))
 387                                return -EFAULT;
 388                        if (!p)
 389                                break;
 390                        argv++;
 391                        if (i++ >= max)
 392                                return -E2BIG;
 393                        cond_resched();
 394                }
 395        }
 396        return i;
 397}
 398
 399/*
 400 * 'copy_strings()' copies argument/environment strings from the old
 401 * processes's memory to the new process's stack.  The call to get_user_pages()
 402 * ensures the destination page is created and not swapped out.
 403 */
 404static int copy_strings(int argc, char __user * __user * argv,
 405                        struct linux_binprm *bprm)
 406{
 407        struct page *kmapped_page = NULL;
 408        char *kaddr = NULL;
 409        unsigned long kpos = 0;
 410        int ret;
 411
 412        while (argc-- > 0) {
 413                char __user *str;
 414                int len;
 415                unsigned long pos;
 416
 417                if (get_user(str, argv+argc) ||
 418                                !(len = strnlen_user(str, MAX_ARG_STRLEN))) {
 419                        ret = -EFAULT;
 420                        goto out;
 421                }
 422
 423                if (!valid_arg_len(bprm, len)) {
 424                        ret = -E2BIG;
 425                        goto out;
 426                }
 427
 428                /* We're going to work our way backwords. */
 429                pos = bprm->p;
 430                str += len;
 431                bprm->p -= len;
 432
 433                while (len > 0) {
 434                        int offset, bytes_to_copy;
 435
 436                        offset = pos % PAGE_SIZE;
 437                        if (offset == 0)
 438                                offset = PAGE_SIZE;
 439
 440                        bytes_to_copy = offset;
 441                        if (bytes_to_copy > len)
 442                                bytes_to_copy = len;
 443
 444                        offset -= bytes_to_copy;
 445                        pos -= bytes_to_copy;
 446                        str -= bytes_to_copy;
 447                        len -= bytes_to_copy;
 448
 449                        if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 450                                struct page *page;
 451
 452                                page = get_arg_page(bprm, pos, 1);
 453                                if (!page) {
 454                                        ret = -E2BIG;
 455                                        goto out;
 456                                }
 457
 458                                if (kmapped_page) {
 459                                        flush_kernel_dcache_page(kmapped_page);
 460                                        kunmap(kmapped_page);
 461                                        put_arg_page(kmapped_page);
 462                                }
 463                                kmapped_page = page;
 464                                kaddr = kmap(kmapped_page);
 465                                kpos = pos & PAGE_MASK;
 466                                flush_arg_page(bprm, kpos, kmapped_page);
 467                        }
 468                        if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 469                                ret = -EFAULT;
 470                                goto out;
 471                        }
 472                }
 473        }
 474        ret = 0;
 475out:
 476        if (kmapped_page) {
 477                flush_kernel_dcache_page(kmapped_page);
 478                kunmap(kmapped_page);
 479                put_arg_page(kmapped_page);
 480        }
 481        return ret;
 482}
 483
 484/*
 485 * Like copy_strings, but get argv and its values from kernel memory.
 486 */
 487int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
 488{
 489        int r;
 490        mm_segment_t oldfs = get_fs();
 491        set_fs(KERNEL_DS);
 492        r = copy_strings(argc, (char __user * __user *)argv, bprm);
 493        set_fs(oldfs);
 494        return r;
 495}
 496EXPORT_SYMBOL(copy_strings_kernel);
 497
 498#ifdef CONFIG_MMU
 499
 500/*
 501 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 502 * the binfmt code determines where the new stack should reside, we shift it to
 503 * its final location.  The process proceeds as follows:
 504 *
 505 * 1) Use shift to calculate the new vma endpoints.
 506 * 2) Extend vma to cover both the old and new ranges.  This ensures the
 507 *    arguments passed to subsequent functions are consistent.
 508 * 3) Move vma's page tables to the new range.
 509 * 4) Free up any cleared pgd range.
 510 * 5) Shrink the vma to cover only the new range.
 511 */
 512static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 513{
 514        struct mm_struct *mm = vma->vm_mm;
 515        unsigned long old_start = vma->vm_start;
 516        unsigned long old_end = vma->vm_end;
 517        unsigned long length = old_end - old_start;
 518        unsigned long new_start = old_start - shift;
 519        unsigned long new_end = old_end - shift;
 520        struct mmu_gather *tlb;
 521
 522        BUG_ON(new_start > new_end);
 523
 524        /*
 525         * ensure there are no vmas between where we want to go
 526         * and where we are
 527         */
 528        if (vma != find_vma(mm, new_start))
 529                return -EFAULT;
 530
 531        /*
 532         * cover the whole range: [new_start, old_end)
 533         */
 534        vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
 535
 536        /*
 537         * move the page tables downwards, on failure we rely on
 538         * process cleanup to remove whatever mess we made.
 539         */
 540        if (length != move_page_tables(vma, old_start,
 541                                       vma, new_start, length))
 542                return -ENOMEM;
 543
 544        lru_add_drain();
 545        tlb = tlb_gather_mmu(mm, 0);
 546        if (new_end > old_start) {
 547                /*
 548                 * when the old and new regions overlap clear from new_end.
 549                 */
 550                free_pgd_range(tlb, new_end, old_end, new_end,
 551                        vma->vm_next ? vma->vm_next->vm_start : 0);
 552        } else {
 553                /*
 554                 * otherwise, clean from old_start; this is done to not touch
 555                 * the address space in [new_end, old_start) some architectures
 556                 * have constraints on va-space that make this illegal (IA64) -
 557                 * for the others its just a little faster.
 558                 */
 559                free_pgd_range(tlb, old_start, old_end, new_end,
 560                        vma->vm_next ? vma->vm_next->vm_start : 0);
 561        }
 562        tlb_finish_mmu(tlb, new_end, old_end);
 563
 564        /*
 565         * shrink the vma to just the new range.
 566         */
 567        vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 568
 569        return 0;
 570}
 571
 572#define EXTRA_STACK_VM_PAGES    20      /* random */
 573
 574/*
 575 * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 576 * the stack is optionally relocated, and some extra space is added.
 577 */
 578int setup_arg_pages(struct linux_binprm *bprm,
 579                    unsigned long stack_top,
 580                    int executable_stack)
 581{
 582        unsigned long ret;
 583        unsigned long stack_shift;
 584        struct mm_struct *mm = current->mm;
 585        struct vm_area_struct *vma = bprm->vma;
 586        struct vm_area_struct *prev = NULL;
 587        unsigned long vm_flags;
 588        unsigned long stack_base;
 589
 590#ifdef CONFIG_STACK_GROWSUP
 591        /* Limit stack size to 1GB */
 592        stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
 593        if (stack_base > (1 << 30))
 594                stack_base = 1 << 30;
 595
 596        /* Make sure we didn't let the argument array grow too large. */
 597        if (vma->vm_end - vma->vm_start > stack_base)
 598                return -ENOMEM;
 599
 600        stack_base = PAGE_ALIGN(stack_top - stack_base);
 601
 602        stack_shift = vma->vm_start - stack_base;
 603        mm->arg_start = bprm->p - stack_shift;
 604        bprm->p = vma->vm_end - stack_shift;
 605#else
 606        stack_top = arch_align_stack(stack_top);
 607        stack_top = PAGE_ALIGN(stack_top);
 608        stack_shift = vma->vm_end - stack_top;
 609
 610        bprm->p -= stack_shift;
 611        mm->arg_start = bprm->p;
 612#endif
 613
 614        if (bprm->loader)
 615                bprm->loader -= stack_shift;
 616        bprm->exec -= stack_shift;
 617
 618        down_write(&mm->mmap_sem);
 619        vm_flags = VM_STACK_FLAGS;
 620
 621        /*
 622         * Adjust stack execute permissions; explicitly enable for
 623         * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 624         * (arch default) otherwise.
 625         */
 626        if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 627                vm_flags |= VM_EXEC;
 628        else if (executable_stack == EXSTACK_DISABLE_X)
 629                vm_flags &= ~VM_EXEC;
 630        vm_flags |= mm->def_flags;
 631
 632        ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 633                        vm_flags);
 634        if (ret)
 635                goto out_unlock;
 636        BUG_ON(prev != vma);
 637
 638        /* Move stack pages down in memory. */
 639        if (stack_shift) {
 640                ret = shift_arg_pages(vma, stack_shift);
 641                if (ret) {
 642                        up_write(&mm->mmap_sem);
 643                        return ret;
 644                }
 645        }
 646
 647#ifdef CONFIG_STACK_GROWSUP
 648        stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 649#else
 650        stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
 651#endif
 652        ret = expand_stack(vma, stack_base);
 653        if (ret)
 654                ret = -EFAULT;
 655
 656out_unlock:
 657        up_write(&mm->mmap_sem);
 658        return 0;
 659}
 660EXPORT_SYMBOL(setup_arg_pages);
 661
 662#endif /* CONFIG_MMU */
 663
 664struct file *open_exec(const char *name)
 665{
 666        struct nameidata nd;
 667        struct file *file;
 668        int err;
 669
 670        err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd,
 671                                FMODE_READ|FMODE_EXEC);
 672        if (err)
 673                goto out;
 674
 675        err = -EACCES;
 676        if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
 677                goto out_path_put;
 678
 679        if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
 680                goto out_path_put;
 681
 682        err = vfs_permission(&nd, MAY_EXEC | MAY_OPEN);
 683        if (err)
 684                goto out_path_put;
 685
 686        file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
 687        if (IS_ERR(file))
 688                return file;
 689
 690        err = deny_write_access(file);
 691        if (err) {
 692                fput(file);
 693                goto out;
 694        }
 695
 696        return file;
 697
 698 out_path_put:
 699        release_open_intent(&nd);
 700        path_put(&nd.path);
 701 out:
 702        return ERR_PTR(err);
 703}
 704EXPORT_SYMBOL(open_exec);
 705
 706int kernel_read(struct file *file, unsigned long offset,
 707        char *addr, unsigned long count)
 708{
 709        mm_segment_t old_fs;
 710        loff_t pos = offset;
 711        int result;
 712
 713        old_fs = get_fs();
 714        set_fs(get_ds());
 715        /* The cast to a user pointer is valid due to the set_fs() */
 716        result = vfs_read(file, (void __user *)addr, count, &pos);
 717        set_fs(old_fs);
 718        return result;
 719}
 720
 721EXPORT_SYMBOL(kernel_read);
 722
 723static int exec_mmap(struct mm_struct *mm)
 724{
 725        struct task_struct *tsk;
 726        struct mm_struct * old_mm, *active_mm;
 727
 728        /* Notify parent that we're no longer interested in the old VM */
 729        tsk = current;
 730        old_mm = current->mm;
 731        mm_release(tsk, old_mm);
 732
 733        if (old_mm) {
 734                /*
 735                 * Make sure that if there is a core dump in progress
 736                 * for the old mm, we get out and die instead of going
 737                 * through with the exec.  We must hold mmap_sem around
 738                 * checking core_state and changing tsk->mm.
 739                 */
 740                down_read(&old_mm->mmap_sem);
 741                if (unlikely(old_mm->core_state)) {
 742                        up_read(&old_mm->mmap_sem);
 743                        return -EINTR;
 744                }
 745        }
 746        task_lock(tsk);
 747        active_mm = tsk->active_mm;
 748        tsk->mm = mm;
 749        tsk->active_mm = mm;
 750        activate_mm(active_mm, mm);
 751        task_unlock(tsk);
 752        arch_pick_mmap_layout(mm);
 753        if (old_mm) {
 754                up_read(&old_mm->mmap_sem);
 755                BUG_ON(active_mm != old_mm);
 756                mm_update_next_owner(old_mm);
 757                mmput(old_mm);
 758                return 0;
 759        }
 760        mmdrop(active_mm);
 761        return 0;
 762}
 763
 764/*
 765 * This function makes sure the current process has its own signal table,
 766 * so that flush_signal_handlers can later reset the handlers without
 767 * disturbing other processes.  (Other processes might share the signal
 768 * table via the CLONE_SIGHAND option to clone().)
 769 */
 770static int de_thread(struct task_struct *tsk)
 771{
 772        struct signal_struct *sig = tsk->signal;
 773        struct sighand_struct *oldsighand = tsk->sighand;
 774        spinlock_t *lock = &oldsighand->siglock;
 775        struct task_struct *leader = NULL;
 776        int count;
 777
 778        if (thread_group_empty(tsk))
 779                goto no_thread_group;
 780
 781        /*
 782         * Kill all other threads in the thread group.
 783         */
 784        spin_lock_irq(lock);
 785        if (signal_group_exit(sig)) {
 786                /*
 787                 * Another group action in progress, just
 788                 * return so that the signal is processed.
 789                 */
 790                spin_unlock_irq(lock);
 791                return -EAGAIN;
 792        }
 793        sig->group_exit_task = tsk;
 794        zap_other_threads(tsk);
 795
 796        /* Account for the thread group leader hanging around: */
 797        count = thread_group_leader(tsk) ? 1 : 2;
 798        sig->notify_count = count;
 799        while (atomic_read(&sig->count) > count) {
 800                __set_current_state(TASK_UNINTERRUPTIBLE);
 801                spin_unlock_irq(lock);
 802                schedule();
 803                spin_lock_irq(lock);
 804        }
 805        spin_unlock_irq(lock);
 806
 807        /*
 808         * At this point all other threads have exited, all we have to
 809         * do is to wait for the thread group leader to become inactive,
 810         * and to assume its PID:
 811         */
 812        if (!thread_group_leader(tsk)) {
 813                leader = tsk->group_leader;
 814
 815                sig->notify_count = -1; /* for exit_notify() */
 816                for (;;) {
 817                        write_lock_irq(&tasklist_lock);
 818                        if (likely(leader->exit_state))
 819                                break;
 820                        __set_current_state(TASK_UNINTERRUPTIBLE);
 821                        write_unlock_irq(&tasklist_lock);
 822                        schedule();
 823                }
 824
 825                /*
 826                 * The only record we have of the real-time age of a
 827                 * process, regardless of execs it's done, is start_time.
 828                 * All the past CPU time is accumulated in signal_struct
 829                 * from sister threads now dead.  But in this non-leader
 830                 * exec, nothing survives from the original leader thread,
 831                 * whose birth marks the true age of this process now.
 832                 * When we take on its identity by switching to its PID, we
 833                 * also take its birthdate (always earlier than our own).
 834                 */
 835                tsk->start_time = leader->start_time;
 836
 837                BUG_ON(!same_thread_group(leader, tsk));
 838                BUG_ON(has_group_leader_pid(tsk));
 839                /*
 840                 * An exec() starts a new thread group with the
 841                 * TGID of the previous thread group. Rehash the
 842                 * two threads with a switched PID, and release
 843                 * the former thread group leader:
 844                 */
 845
 846                /* Become a process group leader with the old leader's pid.
 847                 * The old leader becomes a thread of the this thread group.
 848                 * Note: The old leader also uses this pid until release_task
 849                 *       is called.  Odd but simple and correct.
 850                 */
 851                detach_pid(tsk, PIDTYPE_PID);
 852                tsk->pid = leader->pid;
 853                attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 854                transfer_pid(leader, tsk, PIDTYPE_PGID);
 855                transfer_pid(leader, tsk, PIDTYPE_SID);
 856                list_replace_rcu(&leader->tasks, &tsk->tasks);
 857
 858                tsk->group_leader = tsk;
 859                leader->group_leader = tsk;
 860
 861                tsk->exit_signal = SIGCHLD;
 862
 863                BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 864                leader->exit_state = EXIT_DEAD;
 865
 866                write_unlock_irq(&tasklist_lock);
 867        }
 868
 869        sig->group_exit_task = NULL;
 870        sig->notify_count = 0;
 871
 872no_thread_group:
 873        exit_itimers(sig);
 874        flush_itimer_signals();
 875        if (leader)
 876                release_task(leader);
 877
 878        if (atomic_read(&oldsighand->count) != 1) {
 879                struct sighand_struct *newsighand;
 880                /*
 881                 * This ->sighand is shared with the CLONE_SIGHAND
 882                 * but not CLONE_THREAD task, switch to the new one.
 883                 */
 884                newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 885                if (!newsighand)
 886                        return -ENOMEM;
 887
 888                atomic_set(&newsighand->count, 1);
 889                memcpy(newsighand->action, oldsighand->action,
 890                       sizeof(newsighand->action));
 891
 892                write_lock_irq(&tasklist_lock);
 893                spin_lock(&oldsighand->siglock);
 894                rcu_assign_pointer(tsk->sighand, newsighand);
 895                spin_unlock(&oldsighand->siglock);
 896                write_unlock_irq(&tasklist_lock);
 897
 898                __cleanup_sighand(oldsighand);
 899        }
 900
 901        BUG_ON(!thread_group_leader(tsk));
 902        return 0;
 903}
 904
 905/*
 906 * These functions flushes out all traces of the currently running executable
 907 * so that a new one can be started
 908 */
 909static void flush_old_files(struct files_struct * files)
 910{
 911        long j = -1;
 912        struct fdtable *fdt;
 913
 914        spin_lock(&files->file_lock);
 915        for (;;) {
 916                unsigned long set, i;
 917
 918                j++;
 919                i = j * __NFDBITS;
 920                fdt = files_fdtable(files);
 921                if (i >= fdt->max_fds)
 922                        break;
 923                set = fdt->close_on_exec->fds_bits[j];
 924                if (!set)
 925                        continue;
 926                fdt->close_on_exec->fds_bits[j] = 0;
 927                spin_unlock(&files->file_lock);
 928                for ( ; set ; i++,set >>= 1) {
 929                        if (set & 1) {
 930                                sys_close(i);
 931                        }
 932                }
 933                spin_lock(&files->file_lock);
 934
 935        }
 936        spin_unlock(&files->file_lock);
 937}
 938
 939char *get_task_comm(char *buf, struct task_struct *tsk)
 940{
 941        /* buf must be at least sizeof(tsk->comm) in size */
 942        task_lock(tsk);
 943        strncpy(buf, tsk->comm, sizeof(tsk->comm));
 944        task_unlock(tsk);
 945        return buf;
 946}
 947
 948void set_task_comm(struct task_struct *tsk, char *buf)
 949{
 950        task_lock(tsk);
 951        strlcpy(tsk->comm, buf, sizeof(tsk->comm));
 952        task_unlock(tsk);
 953}
 954
 955int flush_old_exec(struct linux_binprm * bprm)
 956{
 957        char * name;
 958        int i, ch, retval;
 959        char tcomm[sizeof(current->comm)];
 960
 961        /*
 962         * Make sure we have a private signal table and that
 963         * we are unassociated from the previous thread group.
 964         */
 965        retval = de_thread(current);
 966        if (retval)
 967                goto out;
 968
 969        set_mm_exe_file(bprm->mm, bprm->file);
 970
 971        /*
 972         * Release all of the old mmap stuff
 973         */
 974        retval = exec_mmap(bprm->mm);
 975        if (retval)
 976                goto out;
 977
 978        bprm->mm = NULL;                /* We're using it now */
 979
 980        /* This is the point of no return */
 981        current->sas_ss_sp = current->sas_ss_size = 0;
 982
 983        if (current->euid == current->uid && current->egid == current->gid)
 984                set_dumpable(current->mm, 1);
 985        else
 986                set_dumpable(current->mm, suid_dumpable);
 987
 988        name = bprm->filename;
 989
 990        /* Copies the binary name from after last slash */
 991        for (i=0; (ch = *(name++)) != '\0';) {
 992                if (ch == '/')
 993                        i = 0; /* overwrite what we wrote */
 994                else
 995                        if (i < (sizeof(tcomm) - 1))
 996                                tcomm[i++] = ch;
 997        }
 998        tcomm[i] = '\0';
 999        set_task_comm(current, tcomm);
1000
1001        current->flags &= ~PF_RANDOMIZE;
1002        flush_thread();
1003
1004        /* Set the new mm task size. We have to do that late because it may
1005         * depend on TIF_32BIT which is only updated in flush_thread() on
1006         * some architectures like powerpc
1007         */
1008        current->mm->task_size = TASK_SIZE;
1009
1010        if (bprm->e_uid != current->euid || bprm->e_gid != current->egid) {
1011                suid_keys(current);
1012                set_dumpable(current->mm, suid_dumpable);
1013                current->pdeath_signal = 0;
1014        } else if (file_permission(bprm->file, MAY_READ) ||
1015                        (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
1016                suid_keys(current);
1017                set_dumpable(current->mm, suid_dumpable);
1018        }
1019
1020        /* An exec changes our domain. We are no longer part of the thread
1021           group */
1022
1023        current->self_exec_id++;
1024                        
1025        flush_signal_handlers(current, 0);
1026        flush_old_files(current->files);
1027
1028        return 0;
1029
1030out:
1031        return retval;
1032}
1033
1034EXPORT_SYMBOL(flush_old_exec);
1035
1036/* 
1037 * Fill the binprm structure from the inode. 
1038 * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1039 */
1040int prepare_binprm(struct linux_binprm *bprm)
1041{
1042        int mode;
1043        struct inode * inode = bprm->file->f_path.dentry->d_inode;
1044        int retval;
1045
1046        mode = inode->i_mode;
1047        if (bprm->file->f_op == NULL)
1048                return -EACCES;
1049
1050        bprm->e_uid = current->euid;
1051        bprm->e_gid = current->egid;
1052
1053        if(!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1054                /* Set-uid? */
1055                if (mode & S_ISUID) {
1056                        current->personality &= ~PER_CLEAR_ON_SETID;
1057                        bprm->e_uid = inode->i_uid;
1058                }
1059
1060                /* Set-gid? */
1061                /*
1062                 * If setgid is set but no group execute bit then this
1063                 * is a candidate for mandatory locking, not a setgid
1064                 * executable.
1065                 */
1066                if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1067                        current->personality &= ~PER_CLEAR_ON_SETID;
1068                        bprm->e_gid = inode->i_gid;
1069                }
1070        }
1071
1072        /* fill in binprm security blob */
1073        retval = security_bprm_set(bprm);
1074        if (retval)
1075                return retval;
1076
1077        memset(bprm->buf,0,BINPRM_BUF_SIZE);
1078        return kernel_read(bprm->file,0,bprm->buf,BINPRM_BUF_SIZE);
1079}
1080
1081EXPORT_SYMBOL(prepare_binprm);
1082
1083static int unsafe_exec(struct task_struct *p)
1084{
1085        int unsafe = tracehook_unsafe_exec(p);
1086
1087        if (atomic_read(&p->fs->count) > 1 ||
1088            atomic_read(&p->files->count) > 1 ||
1089            atomic_read(&p->sighand->count) > 1)
1090                unsafe |= LSM_UNSAFE_SHARE;
1091
1092        return unsafe;
1093}
1094
1095void compute_creds(struct linux_binprm *bprm)
1096{
1097        int unsafe;
1098
1099        if (bprm->e_uid != current->uid) {
1100                suid_keys(current);
1101                current->pdeath_signal = 0;
1102        }
1103        exec_keys(current);
1104
1105        task_lock(current);
1106        unsafe = unsafe_exec(current);
1107        security_bprm_apply_creds(bprm, unsafe);
1108        task_unlock(current);
1109        security_bprm_post_apply_creds(bprm);
1110}
1111EXPORT_SYMBOL(compute_creds);
1112
1113/*
1114 * Arguments are '\0' separated strings found at the location bprm->p
1115 * points to; chop off the first by relocating brpm->p to right after
1116 * the first '\0' encountered.
1117 */
1118int remove_arg_zero(struct linux_binprm *bprm)
1119{
1120        int ret = 0;
1121        unsigned long offset;
1122        char *kaddr;
1123        struct page *page;
1124
1125        if (!bprm->argc)
1126                return 0;
1127
1128        do {
1129                offset = bprm->p & ~PAGE_MASK;
1130                page = get_arg_page(bprm, bprm->p, 0);
1131                if (!page) {
1132                        ret = -EFAULT;
1133                        goto out;
1134                }
1135                kaddr = kmap_atomic(page, KM_USER0);
1136
1137                for (; offset < PAGE_SIZE && kaddr[offset];
1138                                offset++, bprm->p++)
1139                        ;
1140
1141                kunmap_atomic(kaddr, KM_USER0);
1142                put_arg_page(page);
1143
1144                if (offset == PAGE_SIZE)
1145                        free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1146        } while (offset == PAGE_SIZE);
1147
1148        bprm->p++;
1149        bprm->argc--;
1150        ret = 0;
1151
1152out:
1153        return ret;
1154}
1155EXPORT_SYMBOL(remove_arg_zero);
1156
1157/*
1158 * cycle the list of binary formats handler, until one recognizes the image
1159 */
1160int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1161{
1162        unsigned int depth = bprm->recursion_depth;
1163        int try,retval;
1164        struct linux_binfmt *fmt;
1165#ifdef __alpha__
1166        /* handle /sbin/loader.. */
1167        {
1168            struct exec * eh = (struct exec *) bprm->buf;
1169
1170            if (!bprm->loader && eh->fh.f_magic == 0x183 &&
1171                (eh->fh.f_flags & 0x3000) == 0x3000)
1172            {
1173                struct file * file;
1174                unsigned long loader;
1175
1176                allow_write_access(bprm->file);
1177                fput(bprm->file);
1178                bprm->file = NULL;
1179
1180                loader = bprm->vma->vm_end - sizeof(void *);
1181
1182                file = open_exec("/sbin/loader");
1183                retval = PTR_ERR(file);
1184                if (IS_ERR(file))
1185                        return retval;
1186
1187                /* Remember if the application is TASO.  */
1188                bprm->taso = eh->ah.entry < 0x100000000UL;
1189
1190                bprm->file = file;
1191                bprm->loader = loader;
1192                retval = prepare_binprm(bprm);
1193                if (retval<0)
1194                        return retval;
1195                /* should call search_binary_handler recursively here,
1196                   but it does not matter */
1197            }
1198        }
1199#endif
1200        retval = security_bprm_check(bprm);
1201        if (retval)
1202                return retval;
1203
1204        /* kernel module loader fixup */
1205        /* so we don't try to load run modprobe in kernel space. */
1206        set_fs(USER_DS);
1207
1208        retval = audit_bprm(bprm);
1209        if (retval)
1210                return retval;
1211
1212        retval = -ENOENT;
1213        for (try=0; try<2; try++) {
1214                read_lock(&binfmt_lock);
1215                list_for_each_entry(fmt, &formats, lh) {
1216                        int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1217                        if (!fn)
1218                                continue;
1219                        if (!try_module_get(fmt->module))
1220                                continue;
1221                        read_unlock(&binfmt_lock);
1222                        retval = fn(bprm, regs);
1223                        /*
1224                         * Restore the depth counter to its starting value
1225                         * in this call, so we don't have to rely on every
1226                         * load_binary function to restore it on return.
1227                         */
1228                        bprm->recursion_depth = depth;
1229                        if (retval >= 0) {
1230                                if (depth == 0)
1231                                        tracehook_report_exec(fmt, bprm, regs);
1232                                put_binfmt(fmt);
1233                                allow_write_access(bprm->file);
1234                                if (bprm->file)
1235                                        fput(bprm->file);
1236                                bprm->file = NULL;
1237                                current->did_exec = 1;
1238                                proc_exec_connector(current);
1239                                return retval;
1240                        }
1241                        read_lock(&binfmt_lock);
1242                        put_binfmt(fmt);
1243                        if (retval != -ENOEXEC || bprm->mm == NULL)
1244                                break;
1245                        if (!bprm->file) {
1246                                read_unlock(&binfmt_lock);
1247                                return retval;
1248                        }
1249                }
1250                read_unlock(&binfmt_lock);
1251                if (retval != -ENOEXEC || bprm->mm == NULL) {
1252                        break;
1253#ifdef CONFIG_MODULES
1254                } else {
1255#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1256                        if (printable(bprm->buf[0]) &&
1257                            printable(bprm->buf[1]) &&
1258                            printable(bprm->buf[2]) &&
1259                            printable(bprm->buf[3]))
1260                                break; /* -ENOEXEC */
1261                        request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1262#endif
1263                }
1264        }
1265        return retval;
1266}
1267
1268EXPORT_SYMBOL(search_binary_handler);
1269
1270void free_bprm(struct linux_binprm *bprm)
1271{
1272        free_arg_pages(bprm);
1273        kfree(bprm);
1274}
1275
1276/*
1277 * sys_execve() executes a new program.
1278 */
1279int do_execve(char * filename,
1280        char __user *__user *argv,
1281        char __user *__user *envp,
1282        struct pt_regs * regs)
1283{
1284        struct linux_binprm *bprm;
1285        struct file *file;
1286        struct files_struct *displaced;
1287        int retval;
1288
1289        retval = unshare_files(&displaced);
1290        if (retval)
1291                goto out_ret;
1292
1293        retval = -ENOMEM;
1294        bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1295        if (!bprm)
1296                goto out_files;
1297
1298        file = open_exec(filename);
1299        retval = PTR_ERR(file);
1300        if (IS_ERR(file))
1301                goto out_kfree;
1302
1303        sched_exec();
1304
1305        bprm->file = file;
1306        bprm->filename = filename;
1307        bprm->interp = filename;
1308
1309        retval = bprm_mm_init(bprm);
1310        if (retval)
1311                goto out_file;
1312
1313        bprm->argc = count(argv, MAX_ARG_STRINGS);
1314        if ((retval = bprm->argc) < 0)
1315                goto out_mm;
1316
1317        bprm->envc = count(envp, MAX_ARG_STRINGS);
1318        if ((retval = bprm->envc) < 0)
1319                goto out_mm;
1320
1321        retval = security_bprm_alloc(bprm);
1322        if (retval)
1323                goto out;
1324
1325        retval = prepare_binprm(bprm);
1326        if (retval < 0)
1327                goto out;
1328
1329        retval = copy_strings_kernel(1, &bprm->filename, bprm);
1330        if (retval < 0)
1331                goto out;
1332
1333        bprm->exec = bprm->p;
1334        retval = copy_strings(bprm->envc, envp, bprm);
1335        if (retval < 0)
1336                goto out;
1337
1338        retval = copy_strings(bprm->argc, argv, bprm);
1339        if (retval < 0)
1340                goto out;
1341
1342        current->flags &= ~PF_KTHREAD;
1343        retval = search_binary_handler(bprm,regs);
1344        if (retval >= 0) {
1345                /* execve success */
1346                security_bprm_free(bprm);
1347                acct_update_integrals(current);
1348                free_bprm(bprm);
1349                if (displaced)
1350                        put_files_struct(displaced);
1351                return retval;
1352        }
1353
1354out:
1355        if (bprm->security)
1356                security_bprm_free(bprm);
1357
1358out_mm:
1359        if (bprm->mm)
1360                mmput (bprm->mm);
1361
1362out_file:
1363        if (bprm->file) {
1364                allow_write_access(bprm->file);
1365                fput(bprm->file);
1366        }
1367out_kfree:
1368        free_bprm(bprm);
1369
1370out_files:
1371        if (displaced)
1372                reset_files_struct(displaced);
1373out_ret:
1374        return retval;
1375}
1376
1377int set_binfmt(struct linux_binfmt *new)
1378{
1379        struct linux_binfmt *old = current->binfmt;
1380
1381        if (new) {
1382                if (!try_module_get(new->module))
1383                        return -1;
1384        }
1385        current->binfmt = new;
1386        if (old)
1387                module_put(old->module);
1388        return 0;
1389}
1390
1391EXPORT_SYMBOL(set_binfmt);
1392
1393/* format_corename will inspect the pattern parameter, and output a
1394 * name into corename, which must have space for at least
1395 * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1396 */
1397static int format_corename(char *corename, long signr)
1398{
1399        const char *pat_ptr = core_pattern;
1400        int ispipe = (*pat_ptr == '|');
1401        char *out_ptr = corename;
1402        char *const out_end = corename + CORENAME_MAX_SIZE;
1403        int rc;
1404        int pid_in_pattern = 0;
1405
1406        /* Repeat as long as we have more pattern to process and more output
1407           space */
1408        while (*pat_ptr) {
1409                if (*pat_ptr != '%') {
1410                        if (out_ptr == out_end)
1411                                goto out;
1412                        *out_ptr++ = *pat_ptr++;
1413                } else {
1414                        switch (*++pat_ptr) {
1415                        case 0:
1416                                goto out;
1417                        /* Double percent, output one percent */
1418                        case '%':
1419                                if (out_ptr == out_end)
1420                                        goto out;
1421                                *out_ptr++ = '%';
1422                                break;
1423                        /* pid */
1424                        case 'p':
1425                                pid_in_pattern = 1;
1426                                rc = snprintf(out_ptr, out_end - out_ptr,
1427                                              "%d", task_tgid_vnr(current));
1428                                if (rc > out_end - out_ptr)
1429                                        goto out;
1430                                out_ptr += rc;
1431                                break;
1432                        /* uid */
1433                        case 'u':
1434                                rc = snprintf(out_ptr, out_end - out_ptr,
1435                                              "%d", current->uid);
1436                                if (rc > out_end - out_ptr)
1437                                        goto out;
1438                                out_ptr += rc;
1439                                break;
1440                        /* gid */
1441                        case 'g':
1442                                rc = snprintf(out_ptr, out_end - out_ptr,
1443                                              "%d", current->gid);
1444                                if (rc > out_end - out_ptr)
1445                                        goto out;
1446                                out_ptr += rc;
1447                                break;
1448                        /* signal that caused the coredump */
1449                        case 's':
1450                                rc = snprintf(out_ptr, out_end - out_ptr,
1451                                              "%ld", signr);
1452                                if (rc > out_end - out_ptr)
1453                                        goto out;
1454                                out_ptr += rc;
1455                                break;
1456                        /* UNIX time of coredump */
1457                        case 't': {
1458                                struct timeval tv;
1459                                do_gettimeofday(&tv);
1460                                rc = snprintf(out_ptr, out_end - out_ptr,
1461                                              "%lu", tv.tv_sec);
1462                                if (rc > out_end - out_ptr)
1463                                        goto out;
1464                                out_ptr += rc;
1465                                break;
1466                        }
1467                        /* hostname */
1468                        case 'h':
1469                                down_read(&uts_sem);
1470                                rc = snprintf(out_ptr, out_end - out_ptr,
1471                                              "%s", utsname()->nodename);
1472                                up_read(&uts_sem);
1473                                if (rc > out_end - out_ptr)
1474                                        goto out;
1475                                out_ptr += rc;
1476                                break;
1477                        /* executable */
1478                        case 'e':
1479                                rc = snprintf(out_ptr, out_end - out_ptr,
1480                                              "%s", current->comm);
1481                                if (rc > out_end - out_ptr)
1482                                        goto out;
1483                                out_ptr += rc;
1484                                break;
1485                        /* core limit size */
1486                        case 'c':
1487                                rc = snprintf(out_ptr, out_end - out_ptr,
1488                                              "%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
1489                                if (rc > out_end - out_ptr)
1490                                        goto out;
1491                                out_ptr += rc;
1492                                break;
1493                        default:
1494                                break;
1495                        }
1496                        ++pat_ptr;
1497                }
1498        }
1499        /* Backward compatibility with core_uses_pid:
1500         *
1501         * If core_pattern does not include a %p (as is the default)
1502         * and core_uses_pid is set, then .%pid will be appended to
1503         * the filename. Do not do this for piped commands. */
1504        if (!ispipe && !pid_in_pattern && core_uses_pid) {
1505                rc = snprintf(out_ptr, out_end - out_ptr,
1506                              ".%d", task_tgid_vnr(current));
1507                if (rc > out_end - out_ptr)
1508                        goto out;
1509                out_ptr += rc;
1510        }
1511out:
1512        *out_ptr = 0;
1513        return ispipe;
1514}
1515
1516static int zap_process(struct task_struct *start)
1517{
1518        struct task_struct *t;
1519        int nr = 0;
1520
1521        start->signal->flags = SIGNAL_GROUP_EXIT;
1522        start->signal->group_stop_count = 0;
1523
1524        t = start;
1525        do {
1526                if (t != current && t->mm) {
1527                        sigaddset(&t->pending.signal, SIGKILL);
1528                        signal_wake_up(t, 1);
1529                        nr++;
1530                }
1531        } while_each_thread(start, t);
1532
1533        return nr;
1534}
1535
1536static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1537                                struct core_state *core_state, int exit_code)
1538{
1539        struct task_struct *g, *p;
1540        unsigned long flags;
1541        int nr = -EAGAIN;
1542
1543        spin_lock_irq(&tsk->sighand->siglock);
1544        if (!signal_group_exit(tsk->signal)) {
1545                mm->core_state = core_state;
1546                tsk->signal->group_exit_code = exit_code;
1547                nr = zap_process(tsk);
1548        }
1549        spin_unlock_irq(&tsk->sighand->siglock);
1550        if (unlikely(nr < 0))
1551                return nr;
1552
1553        if (atomic_read(&mm->mm_users) == nr + 1)
1554                goto done;
1555        /*
1556         * We should find and kill all tasks which use this mm, and we should
1557         * count them correctly into ->nr_threads. We don't take tasklist
1558         * lock, but this is safe wrt:
1559         *
1560         * fork:
1561         *      None of sub-threads can fork after zap_process(leader). All
1562         *      processes which were created before this point should be
1563         *      visible to zap_threads() because copy_process() adds the new
1564         *      process to the tail of init_task.tasks list, and lock/unlock
1565         *      of ->siglock provides a memory barrier.
1566         *
1567         * do_exit:
1568         *      The caller holds mm->mmap_sem. This means that the task which
1569         *      uses this mm can't pass exit_mm(), so it can't exit or clear
1570         *      its ->mm.
1571         *
1572         * de_thread:
1573         *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1574         *      we must see either old or new leader, this does not matter.
1575         *      However, it can change p->sighand, so lock_task_sighand(p)
1576         *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1577         *      it can't fail.
1578         *
1579         *      Note also that "g" can be the old leader with ->mm == NULL
1580         *      and already unhashed and thus removed from ->thread_group.
1581         *      This is OK, __unhash_process()->list_del_rcu() does not
1582         *      clear the ->next pointer, we will find the new leader via
1583         *      next_thread().
1584         */
1585        rcu_read_lock();
1586        for_each_process(g) {
1587                if (g == tsk->group_leader)
1588                        continue;
1589                if (g->flags & PF_KTHREAD)
1590                        continue;
1591                p = g;
1592                do {
1593                        if (p->mm) {
1594                                if (unlikely(p->mm == mm)) {
1595                                        lock_task_sighand(p, &flags);
1596                                        nr += zap_process(p);
1597                                        unlock_task_sighand(p, &flags);
1598                                }
1599                                break;
1600                        }
1601                } while_each_thread(g, p);
1602        }
1603        rcu_read_unlock();
1604done:
1605        atomic_set(&core_state->nr_threads, nr);
1606        return nr;
1607}
1608
1609static int coredump_wait(int exit_code, struct core_state *core_state)
1610{
1611        struct task_struct *tsk = current;
1612        struct mm_struct *mm = tsk->mm;
1613        struct completion *vfork_done;
1614        int core_waiters;
1615
1616        init_completion(&core_state->startup);
1617        core_state->dumper.task = tsk;
1618        core_state->dumper.next = NULL;
1619        core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1620        up_write(&mm->mmap_sem);
1621
1622        if (unlikely(core_waiters < 0))
1623                goto fail;
1624
1625        /*
1626         * Make sure nobody is waiting for us to release the VM,
1627         * otherwise we can deadlock when we wait on each other
1628         */
1629        vfork_done = tsk->vfork_done;
1630        if (vfork_done) {
1631                tsk->vfork_done = NULL;
1632                complete(vfork_done);
1633        }
1634
1635        if (core_waiters)
1636                wait_for_completion(&core_state->startup);
1637fail:
1638        return core_waiters;
1639}
1640
1641static void coredump_finish(struct mm_struct *mm)
1642{
1643        struct core_thread *curr, *next;
1644        struct task_struct *task;
1645
1646        next = mm->core_state->dumper.next;
1647        while ((curr = next) != NULL) {
1648                next = curr->next;
1649                task = curr->task;
1650                /*
1651                 * see exit_mm(), curr->task must not see
1652                 * ->task == NULL before we read ->next.
1653                 */
1654                smp_mb();
1655                curr->task = NULL;
1656                wake_up_process(task);
1657        }
1658
1659        mm->core_state = NULL;
1660}
1661
1662/*
1663 * set_dumpable converts traditional three-value dumpable to two flags and
1664 * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1665 * these bits are not changed atomically.  So get_dumpable can observe the
1666 * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1667 * return either old dumpable or new one by paying attention to the order of
1668 * modifying the bits.
1669 *
1670 * dumpable |   mm->flags (binary)
1671 * old  new | initial interim  final
1672 * ---------+-----------------------
1673 *  0    1  |   00      01      01
1674 *  0    2  |   00      10(*)   11
1675 *  1    0  |   01      00      00
1676 *  1    2  |   01      11      11
1677 *  2    0  |   11      10(*)   00
1678 *  2    1  |   11      11      01
1679 *
1680 * (*) get_dumpable regards interim value of 10 as 11.
1681 */
1682void set_dumpable(struct mm_struct *mm, int value)
1683{
1684        switch (value) {
1685        case 0:
1686                clear_bit(MMF_DUMPABLE, &mm->flags);
1687                smp_wmb();
1688                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1689                break;
1690        case 1:
1691                set_bit(MMF_DUMPABLE, &mm->flags);
1692                smp_wmb();
1693                clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1694                break;
1695        case 2:
1696                set_bit(MMF_DUMP_SECURELY, &mm->flags);
1697                smp_wmb();
1698                set_bit(MMF_DUMPABLE, &mm->flags);
1699                break;
1700        }
1701}
1702
1703int get_dumpable(struct mm_struct *mm)
1704{
1705        int ret;
1706
1707        ret = mm->flags & 0x3;
1708        return (ret >= 2) ? 2 : ret;
1709}
1710
1711int do_coredump(long signr, int exit_code, struct pt_regs * regs)
1712{
1713        struct core_state core_state;
1714        char corename[CORENAME_MAX_SIZE + 1];
1715        struct mm_struct *mm = current->mm;
1716        struct linux_binfmt * binfmt;
1717        struct inode * inode;
1718        struct file * file;
1719        int retval = 0;
1720        int fsuid = current->fsuid;
1721        int flag = 0;
1722        int ispipe = 0;
1723        unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
1724        char **helper_argv = NULL;
1725        int helper_argc = 0;
1726        char *delimit;
1727
1728        audit_core_dumps(signr);
1729
1730        binfmt = current->binfmt;
1731        if (!binfmt || !binfmt->core_dump)
1732                goto fail;
1733        down_write(&mm->mmap_sem);
1734        /*
1735         * If another thread got here first, or we are not dumpable, bail out.
1736         */
1737        if (mm->core_state || !get_dumpable(mm)) {
1738                up_write(&mm->mmap_sem);
1739                goto fail;
1740        }
1741
1742        /*
1743         *      We cannot trust fsuid as being the "true" uid of the
1744         *      process nor do we know its entire history. We only know it
1745         *      was tainted so we dump it as root in mode 2.
1746         */
1747        if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */
1748                flag = O_EXCL;          /* Stop rewrite attacks */
1749                current->fsuid = 0;     /* Dump root private */
1750        }
1751
1752        retval = coredump_wait(exit_code, &core_state);
1753        if (retval < 0)
1754                goto fail;
1755
1756        /*
1757         * Clear any false indication of pending signals that might
1758         * be seen by the filesystem code called to write the core file.
1759         */
1760        clear_thread_flag(TIF_SIGPENDING);
1761
1762        /*
1763         * lock_kernel() because format_corename() is controlled by sysctl, which
1764         * uses lock_kernel()
1765         */
1766        lock_kernel();
1767        ispipe = format_corename(corename, signr);
1768        unlock_kernel();
1769        /*
1770         * Don't bother to check the RLIMIT_CORE value if core_pattern points
1771         * to a pipe.  Since we're not writing directly to the filesystem
1772         * RLIMIT_CORE doesn't really apply, as no actual core file will be
1773         * created unless the pipe reader choses to write out the core file
1774         * at which point file size limits and permissions will be imposed
1775         * as it does with any other process
1776         */
1777        if ((!ispipe) && (core_limit < binfmt->min_coredump))
1778                goto fail_unlock;
1779
1780        if (ispipe) {
1781                helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
1782                /* Terminate the string before the first option */
1783                delimit = strchr(corename, ' ');
1784                if (delimit)
1785                        *delimit = '\0';
1786                delimit = strrchr(helper_argv[0], '/');
1787                if (delimit)
1788                        delimit++;
1789                else
1790                        delimit = helper_argv[0];
1791                if (!strcmp(delimit, current->comm)) {
1792                        printk(KERN_NOTICE "Recursive core dump detected, "
1793                                        "aborting\n");
1794                        goto fail_unlock;
1795                }
1796
1797                core_limit = RLIM_INFINITY;
1798
1799                /* SIGPIPE can happen, but it's just never processed */
1800                if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
1801                                &file)) {
1802                        printk(KERN_INFO "Core dump to %s pipe failed\n",
1803                               corename);
1804                        goto fail_unlock;
1805                }
1806        } else
1807                file = filp_open(corename,
1808                                 O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
1809                                 0600);
1810        if (IS_ERR(file))
1811                goto fail_unlock;
1812        inode = file->f_path.dentry->d_inode;
1813        if (inode->i_nlink > 1)
1814                goto close_fail;        /* multiple links - don't dump */
1815        if (!ispipe && d_unhashed(file->f_path.dentry))
1816                goto close_fail;
1817
1818        /* AK: actually i see no reason to not allow this for named pipes etc.,
1819           but keep the previous behaviour for now. */
1820        if (!ispipe && !S_ISREG(inode->i_mode))
1821                goto close_fail;
1822        /*
1823         * Dont allow local users get cute and trick others to coredump
1824         * into their pre-created files:
1825         */
1826        if (inode->i_uid != current->fsuid)
1827                goto close_fail;
1828        if (!file->f_op)
1829                goto close_fail;
1830        if (!file->f_op->write)
1831                goto close_fail;
1832        if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
1833                goto close_fail;
1834
1835        retval = binfmt->core_dump(signr, regs, file, core_limit);
1836
1837        if (retval)
1838                current->signal->group_exit_code |= 0x80;
1839close_fail:
1840        filp_close(file, NULL);
1841fail_unlock:
1842        if (helper_argv)
1843                argv_free(helper_argv);
1844
1845        current->fsuid = fsuid;
1846        coredump_finish(mm);
1847fail:
1848        return retval;
1849}
1850