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synced 2024-08-27 03:10:12 +00:00
![Jann Horn](/assets/img/avatar_default.png)
In both binfmt_elf and binfmt_elf_fdpic, use a new helper dump_vma_snapshot() to take a snapshot of the VMA list (including the gate VMA, if we have one) while protected by the mmap_lock, and then use that snapshot instead of walking the VMA list without locking. An alternative approach would be to keep the mmap_lock held across the entire core dumping operation; however, keeping the mmap_lock locked while we may be blocked for an unbounded amount of time (e.g. because we're dumping to a FUSE filesystem or so) isn't really optimal; the mmap_lock blocks things like the ->release handler of userfaultfd, and we don't really want critical system daemons to grind to a halt just because someone "gifted" them SCM_RIGHTS to an eternally-locked userfaultfd, or something like that. Since both the normal ELF code and the FDPIC ELF code need this functionality (and if any other binfmt wants to add coredump support in the future, they'd probably need it, too), implement this with a common helper in fs/coredump.c. A downside of this approach is that we now need a bigger amount of kernel memory per userspace VMA in the normal ELF case, and that we need O(n) kernel memory in the FDPIC ELF case at all; but 40 bytes per VMA shouldn't be terribly bad. There currently is a data race between stack expansion and anything that reads ->vm_start or ->vm_end under the mmap_lock held in read mode; to mitigate that for core dumping, take the mmap_lock in write mode when taking a snapshot of the VMA hierarchy. (If we only took the mmap_lock in read mode, we could end up with a corrupted core dump if someone does get_user_pages_remote() concurrently. Not really a major problem, but taking the mmap_lock either way works here, so we might as well avoid the issue.) (This doesn't do anything about the existing data races with stack expansion in other mm code.) Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Hugh Dickins <hughd@google.com> Link: http://lkml.kernel.org/r/20200827114932.3572699-6-jannh@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1118 lines
28 KiB
C
1118 lines
28 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/freezer.h>
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#include <linux/mm.h>
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#include <linux/stat.h>
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#include <linux/fcntl.h>
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#include <linux/swap.h>
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#include <linux/ctype.h>
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#include <linux/string.h>
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#include <linux/init.h>
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#include <linux/pagemap.h>
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#include <linux/perf_event.h>
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#include <linux/highmem.h>
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#include <linux/spinlock.h>
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#include <linux/key.h>
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#include <linux/personality.h>
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#include <linux/binfmts.h>
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#include <linux/coredump.h>
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#include <linux/sched/coredump.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/task_stack.h>
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#include <linux/utsname.h>
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#include <linux/pid_namespace.h>
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#include <linux/module.h>
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#include <linux/namei.h>
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#include <linux/mount.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/tsacct_kern.h>
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#include <linux/cn_proc.h>
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#include <linux/audit.h>
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#include <linux/tracehook.h>
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#include <linux/kmod.h>
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#include <linux/fsnotify.h>
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#include <linux/fs_struct.h>
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#include <linux/pipe_fs_i.h>
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#include <linux/oom.h>
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#include <linux/compat.h>
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#include <linux/fs.h>
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#include <linux/path.h>
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#include <linux/timekeeping.h>
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#include <linux/uaccess.h>
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#include <asm/mmu_context.h>
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#include <asm/tlb.h>
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#include <asm/exec.h>
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#include <trace/events/task.h>
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#include "internal.h"
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#include <trace/events/sched.h>
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int core_uses_pid;
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unsigned int core_pipe_limit;
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char core_pattern[CORENAME_MAX_SIZE] = "core";
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static int core_name_size = CORENAME_MAX_SIZE;
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struct core_name {
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char *corename;
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int used, size;
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};
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/* The maximal length of core_pattern is also specified in sysctl.c */
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static int expand_corename(struct core_name *cn, int size)
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{
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char *corename = krealloc(cn->corename, size, GFP_KERNEL);
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if (!corename)
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return -ENOMEM;
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if (size > core_name_size) /* racy but harmless */
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core_name_size = size;
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cn->size = ksize(corename);
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cn->corename = corename;
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return 0;
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}
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static __printf(2, 0) int cn_vprintf(struct core_name *cn, const char *fmt,
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va_list arg)
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{
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int free, need;
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va_list arg_copy;
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again:
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free = cn->size - cn->used;
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va_copy(arg_copy, arg);
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need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy);
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va_end(arg_copy);
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if (need < free) {
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cn->used += need;
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return 0;
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}
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if (!expand_corename(cn, cn->size + need - free + 1))
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goto again;
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return -ENOMEM;
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}
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static __printf(2, 3) int cn_printf(struct core_name *cn, const char *fmt, ...)
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{
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va_list arg;
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int ret;
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va_start(arg, fmt);
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ret = cn_vprintf(cn, fmt, arg);
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va_end(arg);
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return ret;
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}
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static __printf(2, 3)
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int cn_esc_printf(struct core_name *cn, const char *fmt, ...)
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{
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int cur = cn->used;
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va_list arg;
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int ret;
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va_start(arg, fmt);
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ret = cn_vprintf(cn, fmt, arg);
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va_end(arg);
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if (ret == 0) {
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/*
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* Ensure that this coredump name component can't cause the
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* resulting corefile path to consist of a ".." or ".".
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*/
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if ((cn->used - cur == 1 && cn->corename[cur] == '.') ||
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(cn->used - cur == 2 && cn->corename[cur] == '.'
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&& cn->corename[cur+1] == '.'))
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cn->corename[cur] = '!';
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/*
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* Empty names are fishy and could be used to create a "//" in a
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* corefile name, causing the coredump to happen one directory
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* level too high. Enforce that all components of the core
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* pattern are at least one character long.
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*/
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if (cn->used == cur)
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ret = cn_printf(cn, "!");
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}
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for (; cur < cn->used; ++cur) {
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if (cn->corename[cur] == '/')
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cn->corename[cur] = '!';
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}
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return ret;
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}
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static int cn_print_exe_file(struct core_name *cn, bool name_only)
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{
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struct file *exe_file;
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char *pathbuf, *path, *ptr;
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int ret;
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exe_file = get_mm_exe_file(current->mm);
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if (!exe_file)
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return cn_esc_printf(cn, "%s (path unknown)", current->comm);
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pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
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if (!pathbuf) {
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ret = -ENOMEM;
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goto put_exe_file;
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}
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path = file_path(exe_file, pathbuf, PATH_MAX);
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if (IS_ERR(path)) {
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ret = PTR_ERR(path);
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goto free_buf;
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}
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if (name_only) {
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ptr = strrchr(path, '/');
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if (ptr)
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path = ptr + 1;
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}
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ret = cn_esc_printf(cn, "%s", path);
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free_buf:
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kfree(pathbuf);
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put_exe_file:
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fput(exe_file);
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return ret;
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}
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/* format_corename will inspect the pattern parameter, and output a
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* name into corename, which must have space for at least
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* CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
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*/
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static int format_corename(struct core_name *cn, struct coredump_params *cprm,
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size_t **argv, int *argc)
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{
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const struct cred *cred = current_cred();
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const char *pat_ptr = core_pattern;
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int ispipe = (*pat_ptr == '|');
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bool was_space = false;
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int pid_in_pattern = 0;
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int err = 0;
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cn->used = 0;
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cn->corename = NULL;
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if (expand_corename(cn, core_name_size))
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return -ENOMEM;
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cn->corename[0] = '\0';
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if (ispipe) {
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int argvs = sizeof(core_pattern) / 2;
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(*argv) = kmalloc_array(argvs, sizeof(**argv), GFP_KERNEL);
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if (!(*argv))
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return -ENOMEM;
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(*argv)[(*argc)++] = 0;
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++pat_ptr;
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if (!(*pat_ptr))
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return -ENOMEM;
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}
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/* Repeat as long as we have more pattern to process and more output
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space */
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while (*pat_ptr) {
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/*
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* Split on spaces before doing template expansion so that
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* %e and %E don't get split if they have spaces in them
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*/
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if (ispipe) {
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if (isspace(*pat_ptr)) {
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was_space = true;
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pat_ptr++;
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continue;
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} else if (was_space) {
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was_space = false;
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err = cn_printf(cn, "%c", '\0');
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if (err)
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return err;
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(*argv)[(*argc)++] = cn->used;
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}
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}
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if (*pat_ptr != '%') {
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err = cn_printf(cn, "%c", *pat_ptr++);
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} else {
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switch (*++pat_ptr) {
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/* single % at the end, drop that */
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case 0:
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goto out;
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/* Double percent, output one percent */
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case '%':
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err = cn_printf(cn, "%c", '%');
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break;
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/* pid */
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case 'p':
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pid_in_pattern = 1;
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err = cn_printf(cn, "%d",
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task_tgid_vnr(current));
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break;
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/* global pid */
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case 'P':
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err = cn_printf(cn, "%d",
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task_tgid_nr(current));
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break;
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case 'i':
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err = cn_printf(cn, "%d",
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task_pid_vnr(current));
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break;
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case 'I':
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err = cn_printf(cn, "%d",
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task_pid_nr(current));
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break;
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/* uid */
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case 'u':
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err = cn_printf(cn, "%u",
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from_kuid(&init_user_ns,
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cred->uid));
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break;
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/* gid */
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case 'g':
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err = cn_printf(cn, "%u",
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from_kgid(&init_user_ns,
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cred->gid));
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break;
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case 'd':
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err = cn_printf(cn, "%d",
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__get_dumpable(cprm->mm_flags));
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break;
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/* signal that caused the coredump */
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case 's':
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err = cn_printf(cn, "%d",
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cprm->siginfo->si_signo);
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break;
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/* UNIX time of coredump */
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case 't': {
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time64_t time;
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time = ktime_get_real_seconds();
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err = cn_printf(cn, "%lld", time);
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break;
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}
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/* hostname */
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case 'h':
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down_read(&uts_sem);
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err = cn_esc_printf(cn, "%s",
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utsname()->nodename);
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up_read(&uts_sem);
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break;
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/* executable, could be changed by prctl PR_SET_NAME etc */
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case 'e':
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err = cn_esc_printf(cn, "%s", current->comm);
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break;
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/* file name of executable */
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case 'f':
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err = cn_print_exe_file(cn, true);
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break;
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case 'E':
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err = cn_print_exe_file(cn, false);
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break;
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/* core limit size */
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case 'c':
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err = cn_printf(cn, "%lu",
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rlimit(RLIMIT_CORE));
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break;
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default:
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break;
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}
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++pat_ptr;
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}
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if (err)
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return err;
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}
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out:
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/* Backward compatibility with core_uses_pid:
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*
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* If core_pattern does not include a %p (as is the default)
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* and core_uses_pid is set, then .%pid will be appended to
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* the filename. Do not do this for piped commands. */
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if (!ispipe && !pid_in_pattern && core_uses_pid) {
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err = cn_printf(cn, ".%d", task_tgid_vnr(current));
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if (err)
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return err;
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}
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return ispipe;
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}
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static int zap_process(struct task_struct *start, int exit_code, int flags)
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{
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struct task_struct *t;
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int nr = 0;
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/* ignore all signals except SIGKILL, see prepare_signal() */
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start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
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start->signal->group_exit_code = exit_code;
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start->signal->group_stop_count = 0;
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for_each_thread(start, t) {
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task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
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if (t != current && t->mm) {
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sigaddset(&t->pending.signal, SIGKILL);
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signal_wake_up(t, 1);
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nr++;
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}
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}
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return nr;
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}
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static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
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struct core_state *core_state, int exit_code)
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{
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struct task_struct *g, *p;
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unsigned long flags;
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int nr = -EAGAIN;
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spin_lock_irq(&tsk->sighand->siglock);
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if (!signal_group_exit(tsk->signal)) {
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mm->core_state = core_state;
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tsk->signal->group_exit_task = tsk;
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nr = zap_process(tsk, exit_code, 0);
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clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
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}
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spin_unlock_irq(&tsk->sighand->siglock);
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if (unlikely(nr < 0))
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return nr;
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tsk->flags |= PF_DUMPCORE;
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if (atomic_read(&mm->mm_users) == nr + 1)
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goto done;
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/*
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* We should find and kill all tasks which use this mm, and we should
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* count them correctly into ->nr_threads. We don't take tasklist
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* lock, but this is safe wrt:
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*
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* fork:
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* None of sub-threads can fork after zap_process(leader). All
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* processes which were created before this point should be
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* visible to zap_threads() because copy_process() adds the new
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* process to the tail of init_task.tasks list, and lock/unlock
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* of ->siglock provides a memory barrier.
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*
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* do_exit:
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* The caller holds mm->mmap_lock. This means that the task which
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* uses this mm can't pass exit_mm(), so it can't exit or clear
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* its ->mm.
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*
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* de_thread:
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* It does list_replace_rcu(&leader->tasks, ¤t->tasks),
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* we must see either old or new leader, this does not matter.
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* However, it can change p->sighand, so lock_task_sighand(p)
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* must be used. Since p->mm != NULL and we hold ->mmap_lock
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* it can't fail.
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*
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* Note also that "g" can be the old leader with ->mm == NULL
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* and already unhashed and thus removed from ->thread_group.
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* This is OK, __unhash_process()->list_del_rcu() does not
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* clear the ->next pointer, we will find the new leader via
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* next_thread().
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*/
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rcu_read_lock();
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for_each_process(g) {
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if (g == tsk->group_leader)
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continue;
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if (g->flags & PF_KTHREAD)
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continue;
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|
|
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for_each_thread(g, p) {
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if (unlikely(!p->mm))
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continue;
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if (unlikely(p->mm == mm)) {
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lock_task_sighand(p, &flags);
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nr += zap_process(p, exit_code,
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SIGNAL_GROUP_EXIT);
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unlock_task_sighand(p, &flags);
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}
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break;
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}
|
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}
|
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rcu_read_unlock();
|
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done:
|
|
atomic_set(&core_state->nr_threads, nr);
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return nr;
|
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}
|
|
|
|
static int coredump_wait(int exit_code, struct core_state *core_state)
|
|
{
|
|
struct task_struct *tsk = current;
|
|
struct mm_struct *mm = tsk->mm;
|
|
int core_waiters = -EBUSY;
|
|
|
|
init_completion(&core_state->startup);
|
|
core_state->dumper.task = tsk;
|
|
core_state->dumper.next = NULL;
|
|
|
|
if (mmap_write_lock_killable(mm))
|
|
return -EINTR;
|
|
|
|
if (!mm->core_state)
|
|
core_waiters = zap_threads(tsk, mm, core_state, exit_code);
|
|
mmap_write_unlock(mm);
|
|
|
|
if (core_waiters > 0) {
|
|
struct core_thread *ptr;
|
|
|
|
freezer_do_not_count();
|
|
wait_for_completion(&core_state->startup);
|
|
freezer_count();
|
|
/*
|
|
* Wait for all the threads to become inactive, so that
|
|
* all the thread context (extended register state, like
|
|
* fpu etc) gets copied to the memory.
|
|
*/
|
|
ptr = core_state->dumper.next;
|
|
while (ptr != NULL) {
|
|
wait_task_inactive(ptr->task, 0);
|
|
ptr = ptr->next;
|
|
}
|
|
}
|
|
|
|
return core_waiters;
|
|
}
|
|
|
|
static void coredump_finish(struct mm_struct *mm, bool core_dumped)
|
|
{
|
|
struct core_thread *curr, *next;
|
|
struct task_struct *task;
|
|
|
|
spin_lock_irq(¤t->sighand->siglock);
|
|
if (core_dumped && !__fatal_signal_pending(current))
|
|
current->signal->group_exit_code |= 0x80;
|
|
current->signal->group_exit_task = NULL;
|
|
current->signal->flags = SIGNAL_GROUP_EXIT;
|
|
spin_unlock_irq(¤t->sighand->siglock);
|
|
|
|
next = mm->core_state->dumper.next;
|
|
while ((curr = next) != NULL) {
|
|
next = curr->next;
|
|
task = curr->task;
|
|
/*
|
|
* see exit_mm(), curr->task must not see
|
|
* ->task == NULL before we read ->next.
|
|
*/
|
|
smp_mb();
|
|
curr->task = NULL;
|
|
wake_up_process(task);
|
|
}
|
|
|
|
mm->core_state = NULL;
|
|
}
|
|
|
|
static bool dump_interrupted(void)
|
|
{
|
|
/*
|
|
* SIGKILL or freezing() interrupt the coredumping. Perhaps we
|
|
* can do try_to_freeze() and check __fatal_signal_pending(),
|
|
* but then we need to teach dump_write() to restart and clear
|
|
* TIF_SIGPENDING.
|
|
*/
|
|
return signal_pending(current);
|
|
}
|
|
|
|
static void wait_for_dump_helpers(struct file *file)
|
|
{
|
|
struct pipe_inode_info *pipe = file->private_data;
|
|
|
|
pipe_lock(pipe);
|
|
pipe->readers++;
|
|
pipe->writers--;
|
|
wake_up_interruptible_sync(&pipe->rd_wait);
|
|
kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
|
|
pipe_unlock(pipe);
|
|
|
|
/*
|
|
* We actually want wait_event_freezable() but then we need
|
|
* to clear TIF_SIGPENDING and improve dump_interrupted().
|
|
*/
|
|
wait_event_interruptible(pipe->rd_wait, pipe->readers == 1);
|
|
|
|
pipe_lock(pipe);
|
|
pipe->readers--;
|
|
pipe->writers++;
|
|
pipe_unlock(pipe);
|
|
}
|
|
|
|
/*
|
|
* umh_pipe_setup
|
|
* helper function to customize the process used
|
|
* to collect the core in userspace. Specifically
|
|
* it sets up a pipe and installs it as fd 0 (stdin)
|
|
* for the process. Returns 0 on success, or
|
|
* PTR_ERR on failure.
|
|
* Note that it also sets the core limit to 1. This
|
|
* is a special value that we use to trap recursive
|
|
* core dumps
|
|
*/
|
|
static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
|
|
{
|
|
struct file *files[2];
|
|
struct coredump_params *cp = (struct coredump_params *)info->data;
|
|
int err = create_pipe_files(files, 0);
|
|
if (err)
|
|
return err;
|
|
|
|
cp->file = files[1];
|
|
|
|
err = replace_fd(0, files[0], 0);
|
|
fput(files[0]);
|
|
/* and disallow core files too */
|
|
current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
|
|
|
|
return err;
|
|
}
|
|
|
|
void do_coredump(const kernel_siginfo_t *siginfo)
|
|
{
|
|
struct core_state core_state;
|
|
struct core_name cn;
|
|
struct mm_struct *mm = current->mm;
|
|
struct linux_binfmt * binfmt;
|
|
const struct cred *old_cred;
|
|
struct cred *cred;
|
|
int retval = 0;
|
|
int ispipe;
|
|
size_t *argv = NULL;
|
|
int argc = 0;
|
|
struct files_struct *displaced;
|
|
/* require nonrelative corefile path and be extra careful */
|
|
bool need_suid_safe = false;
|
|
bool core_dumped = false;
|
|
static atomic_t core_dump_count = ATOMIC_INIT(0);
|
|
struct coredump_params cprm = {
|
|
.siginfo = siginfo,
|
|
.regs = signal_pt_regs(),
|
|
.limit = rlimit(RLIMIT_CORE),
|
|
/*
|
|
* We must use the same mm->flags while dumping core to avoid
|
|
* inconsistency of bit flags, since this flag is not protected
|
|
* by any locks.
|
|
*/
|
|
.mm_flags = mm->flags,
|
|
};
|
|
|
|
audit_core_dumps(siginfo->si_signo);
|
|
|
|
binfmt = mm->binfmt;
|
|
if (!binfmt || !binfmt->core_dump)
|
|
goto fail;
|
|
if (!__get_dumpable(cprm.mm_flags))
|
|
goto fail;
|
|
|
|
cred = prepare_creds();
|
|
if (!cred)
|
|
goto fail;
|
|
/*
|
|
* We cannot trust fsuid as being the "true" uid of the process
|
|
* nor do we know its entire history. We only know it was tainted
|
|
* so we dump it as root in mode 2, and only into a controlled
|
|
* environment (pipe handler or fully qualified path).
|
|
*/
|
|
if (__get_dumpable(cprm.mm_flags) == SUID_DUMP_ROOT) {
|
|
/* Setuid core dump mode */
|
|
cred->fsuid = GLOBAL_ROOT_UID; /* Dump root private */
|
|
need_suid_safe = true;
|
|
}
|
|
|
|
retval = coredump_wait(siginfo->si_signo, &core_state);
|
|
if (retval < 0)
|
|
goto fail_creds;
|
|
|
|
old_cred = override_creds(cred);
|
|
|
|
ispipe = format_corename(&cn, &cprm, &argv, &argc);
|
|
|
|
if (ispipe) {
|
|
int argi;
|
|
int dump_count;
|
|
char **helper_argv;
|
|
struct subprocess_info *sub_info;
|
|
|
|
if (ispipe < 0) {
|
|
printk(KERN_WARNING "format_corename failed\n");
|
|
printk(KERN_WARNING "Aborting core\n");
|
|
goto fail_unlock;
|
|
}
|
|
|
|
if (cprm.limit == 1) {
|
|
/* See umh_pipe_setup() which sets RLIMIT_CORE = 1.
|
|
*
|
|
* Normally core limits are irrelevant to pipes, since
|
|
* we're not writing to the file system, but we use
|
|
* cprm.limit of 1 here as a special value, this is a
|
|
* consistent way to catch recursive crashes.
|
|
* We can still crash if the core_pattern binary sets
|
|
* RLIM_CORE = !1, but it runs as root, and can do
|
|
* lots of stupid things.
|
|
*
|
|
* Note that we use task_tgid_vnr here to grab the pid
|
|
* of the process group leader. That way we get the
|
|
* right pid if a thread in a multi-threaded
|
|
* core_pattern process dies.
|
|
*/
|
|
printk(KERN_WARNING
|
|
"Process %d(%s) has RLIMIT_CORE set to 1\n",
|
|
task_tgid_vnr(current), current->comm);
|
|
printk(KERN_WARNING "Aborting core\n");
|
|
goto fail_unlock;
|
|
}
|
|
cprm.limit = RLIM_INFINITY;
|
|
|
|
dump_count = atomic_inc_return(&core_dump_count);
|
|
if (core_pipe_limit && (core_pipe_limit < dump_count)) {
|
|
printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
|
|
task_tgid_vnr(current), current->comm);
|
|
printk(KERN_WARNING "Skipping core dump\n");
|
|
goto fail_dropcount;
|
|
}
|
|
|
|
helper_argv = kmalloc_array(argc + 1, sizeof(*helper_argv),
|
|
GFP_KERNEL);
|
|
if (!helper_argv) {
|
|
printk(KERN_WARNING "%s failed to allocate memory\n",
|
|
__func__);
|
|
goto fail_dropcount;
|
|
}
|
|
for (argi = 0; argi < argc; argi++)
|
|
helper_argv[argi] = cn.corename + argv[argi];
|
|
helper_argv[argi] = NULL;
|
|
|
|
retval = -ENOMEM;
|
|
sub_info = call_usermodehelper_setup(helper_argv[0],
|
|
helper_argv, NULL, GFP_KERNEL,
|
|
umh_pipe_setup, NULL, &cprm);
|
|
if (sub_info)
|
|
retval = call_usermodehelper_exec(sub_info,
|
|
UMH_WAIT_EXEC);
|
|
|
|
kfree(helper_argv);
|
|
if (retval) {
|
|
printk(KERN_INFO "Core dump to |%s pipe failed\n",
|
|
cn.corename);
|
|
goto close_fail;
|
|
}
|
|
} else {
|
|
struct inode *inode;
|
|
int open_flags = O_CREAT | O_RDWR | O_NOFOLLOW |
|
|
O_LARGEFILE | O_EXCL;
|
|
|
|
if (cprm.limit < binfmt->min_coredump)
|
|
goto fail_unlock;
|
|
|
|
if (need_suid_safe && cn.corename[0] != '/') {
|
|
printk(KERN_WARNING "Pid %d(%s) can only dump core "\
|
|
"to fully qualified path!\n",
|
|
task_tgid_vnr(current), current->comm);
|
|
printk(KERN_WARNING "Skipping core dump\n");
|
|
goto fail_unlock;
|
|
}
|
|
|
|
/*
|
|
* Unlink the file if it exists unless this is a SUID
|
|
* binary - in that case, we're running around with root
|
|
* privs and don't want to unlink another user's coredump.
|
|
*/
|
|
if (!need_suid_safe) {
|
|
/*
|
|
* If it doesn't exist, that's fine. If there's some
|
|
* other problem, we'll catch it at the filp_open().
|
|
*/
|
|
do_unlinkat(AT_FDCWD, getname_kernel(cn.corename));
|
|
}
|
|
|
|
/*
|
|
* There is a race between unlinking and creating the
|
|
* file, but if that causes an EEXIST here, that's
|
|
* fine - another process raced with us while creating
|
|
* the corefile, and the other process won. To userspace,
|
|
* what matters is that at least one of the two processes
|
|
* writes its coredump successfully, not which one.
|
|
*/
|
|
if (need_suid_safe) {
|
|
/*
|
|
* Using user namespaces, normal user tasks can change
|
|
* their current->fs->root to point to arbitrary
|
|
* directories. Since the intention of the "only dump
|
|
* with a fully qualified path" rule is to control where
|
|
* coredumps may be placed using root privileges,
|
|
* current->fs->root must not be used. Instead, use the
|
|
* root directory of init_task.
|
|
*/
|
|
struct path root;
|
|
|
|
task_lock(&init_task);
|
|
get_fs_root(init_task.fs, &root);
|
|
task_unlock(&init_task);
|
|
cprm.file = file_open_root(root.dentry, root.mnt,
|
|
cn.corename, open_flags, 0600);
|
|
path_put(&root);
|
|
} else {
|
|
cprm.file = filp_open(cn.corename, open_flags, 0600);
|
|
}
|
|
if (IS_ERR(cprm.file))
|
|
goto fail_unlock;
|
|
|
|
inode = file_inode(cprm.file);
|
|
if (inode->i_nlink > 1)
|
|
goto close_fail;
|
|
if (d_unhashed(cprm.file->f_path.dentry))
|
|
goto close_fail;
|
|
/*
|
|
* AK: actually i see no reason to not allow this for named
|
|
* pipes etc, but keep the previous behaviour for now.
|
|
*/
|
|
if (!S_ISREG(inode->i_mode))
|
|
goto close_fail;
|
|
/*
|
|
* Don't dump core if the filesystem changed owner or mode
|
|
* of the file during file creation. This is an issue when
|
|
* a process dumps core while its cwd is e.g. on a vfat
|
|
* filesystem.
|
|
*/
|
|
if (!uid_eq(inode->i_uid, current_fsuid()))
|
|
goto close_fail;
|
|
if ((inode->i_mode & 0677) != 0600)
|
|
goto close_fail;
|
|
if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
|
|
goto close_fail;
|
|
if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
|
|
goto close_fail;
|
|
}
|
|
|
|
/* get us an unshared descriptor table; almost always a no-op */
|
|
retval = unshare_files(&displaced);
|
|
if (retval)
|
|
goto close_fail;
|
|
if (displaced)
|
|
put_files_struct(displaced);
|
|
if (!dump_interrupted()) {
|
|
/*
|
|
* umh disabled with CONFIG_STATIC_USERMODEHELPER_PATH="" would
|
|
* have this set to NULL.
|
|
*/
|
|
if (!cprm.file) {
|
|
pr_info("Core dump to |%s disabled\n", cn.corename);
|
|
goto close_fail;
|
|
}
|
|
file_start_write(cprm.file);
|
|
core_dumped = binfmt->core_dump(&cprm);
|
|
file_end_write(cprm.file);
|
|
}
|
|
if (ispipe && core_pipe_limit)
|
|
wait_for_dump_helpers(cprm.file);
|
|
close_fail:
|
|
if (cprm.file)
|
|
filp_close(cprm.file, NULL);
|
|
fail_dropcount:
|
|
if (ispipe)
|
|
atomic_dec(&core_dump_count);
|
|
fail_unlock:
|
|
kfree(argv);
|
|
kfree(cn.corename);
|
|
coredump_finish(mm, core_dumped);
|
|
revert_creds(old_cred);
|
|
fail_creds:
|
|
put_cred(cred);
|
|
fail:
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Core dumping helper functions. These are the only things you should
|
|
* do on a core-file: use only these functions to write out all the
|
|
* necessary info.
|
|
*/
|
|
int dump_emit(struct coredump_params *cprm, const void *addr, int nr)
|
|
{
|
|
struct file *file = cprm->file;
|
|
loff_t pos = file->f_pos;
|
|
ssize_t n;
|
|
if (cprm->written + nr > cprm->limit)
|
|
return 0;
|
|
|
|
|
|
if (dump_interrupted())
|
|
return 0;
|
|
n = __kernel_write(file, addr, nr, &pos);
|
|
if (n != nr)
|
|
return 0;
|
|
file->f_pos = pos;
|
|
cprm->written += n;
|
|
cprm->pos += n;
|
|
|
|
return 1;
|
|
}
|
|
EXPORT_SYMBOL(dump_emit);
|
|
|
|
int dump_skip(struct coredump_params *cprm, size_t nr)
|
|
{
|
|
static char zeroes[PAGE_SIZE];
|
|
struct file *file = cprm->file;
|
|
if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
|
|
if (dump_interrupted() ||
|
|
file->f_op->llseek(file, nr, SEEK_CUR) < 0)
|
|
return 0;
|
|
cprm->pos += nr;
|
|
return 1;
|
|
} else {
|
|
while (nr > PAGE_SIZE) {
|
|
if (!dump_emit(cprm, zeroes, PAGE_SIZE))
|
|
return 0;
|
|
nr -= PAGE_SIZE;
|
|
}
|
|
return dump_emit(cprm, zeroes, nr);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(dump_skip);
|
|
|
|
#ifdef CONFIG_ELF_CORE
|
|
int dump_user_range(struct coredump_params *cprm, unsigned long start,
|
|
unsigned long len)
|
|
{
|
|
unsigned long addr;
|
|
|
|
for (addr = start; addr < start + len; addr += PAGE_SIZE) {
|
|
struct page *page;
|
|
int stop;
|
|
|
|
/*
|
|
* To avoid having to allocate page tables for virtual address
|
|
* ranges that have never been used yet, and also to make it
|
|
* easy to generate sparse core files, use a helper that returns
|
|
* NULL when encountering an empty page table entry that would
|
|
* otherwise have been filled with the zero page.
|
|
*/
|
|
page = get_dump_page(addr);
|
|
if (page) {
|
|
void *kaddr = kmap(page);
|
|
|
|
stop = !dump_emit(cprm, kaddr, PAGE_SIZE);
|
|
kunmap(page);
|
|
put_page(page);
|
|
} else {
|
|
stop = !dump_skip(cprm, PAGE_SIZE);
|
|
}
|
|
if (stop)
|
|
return 0;
|
|
}
|
|
return 1;
|
|
}
|
|
#endif
|
|
|
|
int dump_align(struct coredump_params *cprm, int align)
|
|
{
|
|
unsigned mod = cprm->pos & (align - 1);
|
|
if (align & (align - 1))
|
|
return 0;
|
|
return mod ? dump_skip(cprm, align - mod) : 1;
|
|
}
|
|
EXPORT_SYMBOL(dump_align);
|
|
|
|
/*
|
|
* Ensures that file size is big enough to contain the current file
|
|
* postion. This prevents gdb from complaining about a truncated file
|
|
* if the last "write" to the file was dump_skip.
|
|
*/
|
|
void dump_truncate(struct coredump_params *cprm)
|
|
{
|
|
struct file *file = cprm->file;
|
|
loff_t offset;
|
|
|
|
if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
|
|
offset = file->f_op->llseek(file, 0, SEEK_CUR);
|
|
if (i_size_read(file->f_mapping->host) < offset)
|
|
do_truncate(file->f_path.dentry, offset, 0, file);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(dump_truncate);
|
|
|
|
/*
|
|
* The purpose of always_dump_vma() is to make sure that special kernel mappings
|
|
* that are useful for post-mortem analysis are included in every core dump.
|
|
* In that way we ensure that the core dump is fully interpretable later
|
|
* without matching up the same kernel and hardware config to see what PC values
|
|
* meant. These special mappings include - vDSO, vsyscall, and other
|
|
* architecture specific mappings
|
|
*/
|
|
static bool always_dump_vma(struct vm_area_struct *vma)
|
|
{
|
|
/* Any vsyscall mappings? */
|
|
if (vma == get_gate_vma(vma->vm_mm))
|
|
return true;
|
|
|
|
/*
|
|
* Assume that all vmas with a .name op should always be dumped.
|
|
* If this changes, a new vm_ops field can easily be added.
|
|
*/
|
|
if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops->name(vma))
|
|
return true;
|
|
|
|
/*
|
|
* arch_vma_name() returns non-NULL for special architecture mappings,
|
|
* such as vDSO sections.
|
|
*/
|
|
if (arch_vma_name(vma))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Decide how much of @vma's contents should be included in a core dump.
|
|
*/
|
|
static unsigned long vma_dump_size(struct vm_area_struct *vma,
|
|
unsigned long mm_flags)
|
|
{
|
|
#define FILTER(type) (mm_flags & (1UL << MMF_DUMP_##type))
|
|
|
|
/* always dump the vdso and vsyscall sections */
|
|
if (always_dump_vma(vma))
|
|
goto whole;
|
|
|
|
if (vma->vm_flags & VM_DONTDUMP)
|
|
return 0;
|
|
|
|
/* support for DAX */
|
|
if (vma_is_dax(vma)) {
|
|
if ((vma->vm_flags & VM_SHARED) && FILTER(DAX_SHARED))
|
|
goto whole;
|
|
if (!(vma->vm_flags & VM_SHARED) && FILTER(DAX_PRIVATE))
|
|
goto whole;
|
|
return 0;
|
|
}
|
|
|
|
/* Hugetlb memory check */
|
|
if (is_vm_hugetlb_page(vma)) {
|
|
if ((vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_SHARED))
|
|
goto whole;
|
|
if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
|
|
goto whole;
|
|
return 0;
|
|
}
|
|
|
|
/* Do not dump I/O mapped devices or special mappings */
|
|
if (vma->vm_flags & VM_IO)
|
|
return 0;
|
|
|
|
/* By default, dump shared memory if mapped from an anonymous file. */
|
|
if (vma->vm_flags & VM_SHARED) {
|
|
if (file_inode(vma->vm_file)->i_nlink == 0 ?
|
|
FILTER(ANON_SHARED) : FILTER(MAPPED_SHARED))
|
|
goto whole;
|
|
return 0;
|
|
}
|
|
|
|
/* Dump segments that have been written to. */
|
|
if ((!IS_ENABLED(CONFIG_MMU) || vma->anon_vma) && FILTER(ANON_PRIVATE))
|
|
goto whole;
|
|
if (vma->vm_file == NULL)
|
|
return 0;
|
|
|
|
if (FILTER(MAPPED_PRIVATE))
|
|
goto whole;
|
|
|
|
/*
|
|
* If this is the beginning of an executable file mapping,
|
|
* dump the first page to aid in determining what was mapped here.
|
|
*/
|
|
if (FILTER(ELF_HEADERS) &&
|
|
vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) &&
|
|
(READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0)
|
|
return PAGE_SIZE;
|
|
|
|
#undef FILTER
|
|
|
|
return 0;
|
|
|
|
whole:
|
|
return vma->vm_end - vma->vm_start;
|
|
}
|
|
|
|
static struct vm_area_struct *first_vma(struct task_struct *tsk,
|
|
struct vm_area_struct *gate_vma)
|
|
{
|
|
struct vm_area_struct *ret = tsk->mm->mmap;
|
|
|
|
if (ret)
|
|
return ret;
|
|
return gate_vma;
|
|
}
|
|
|
|
/*
|
|
* Helper function for iterating across a vma list. It ensures that the caller
|
|
* will visit `gate_vma' prior to terminating the search.
|
|
*/
|
|
static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma,
|
|
struct vm_area_struct *gate_vma)
|
|
{
|
|
struct vm_area_struct *ret;
|
|
|
|
ret = this_vma->vm_next;
|
|
if (ret)
|
|
return ret;
|
|
if (this_vma == gate_vma)
|
|
return NULL;
|
|
return gate_vma;
|
|
}
|
|
|
|
/*
|
|
* Under the mmap_lock, take a snapshot of relevant information about the task's
|
|
* VMAs.
|
|
*/
|
|
int dump_vma_snapshot(struct coredump_params *cprm, int *vma_count,
|
|
struct core_vma_metadata **vma_meta,
|
|
size_t *vma_data_size_ptr)
|
|
{
|
|
struct vm_area_struct *vma, *gate_vma;
|
|
struct mm_struct *mm = current->mm;
|
|
int i;
|
|
size_t vma_data_size = 0;
|
|
|
|
/*
|
|
* Once the stack expansion code is fixed to not change VMA bounds
|
|
* under mmap_lock in read mode, this can be changed to take the
|
|
* mmap_lock in read mode.
|
|
*/
|
|
if (mmap_write_lock_killable(mm))
|
|
return -EINTR;
|
|
|
|
gate_vma = get_gate_vma(mm);
|
|
*vma_count = mm->map_count + (gate_vma ? 1 : 0);
|
|
|
|
*vma_meta = kvmalloc_array(*vma_count, sizeof(**vma_meta), GFP_KERNEL);
|
|
if (!*vma_meta) {
|
|
mmap_write_unlock(mm);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
for (i = 0, vma = first_vma(current, gate_vma); vma != NULL;
|
|
vma = next_vma(vma, gate_vma), i++) {
|
|
struct core_vma_metadata *m = (*vma_meta) + i;
|
|
|
|
m->start = vma->vm_start;
|
|
m->end = vma->vm_end;
|
|
m->flags = vma->vm_flags;
|
|
m->dump_size = vma_dump_size(vma, cprm->mm_flags);
|
|
|
|
vma_data_size += m->dump_size;
|
|
}
|
|
|
|
mmap_write_unlock(mm);
|
|
|
|
if (WARN_ON(i != *vma_count))
|
|
return -EFAULT;
|
|
|
|
*vma_data_size_ptr = vma_data_size;
|
|
return 0;
|
|
}
|