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![Michal Hocko](/assets/img/avatar_default.png)
GFP_TEMPORARY was introduced by commit e12ba74d8f
("Group short-lived
and reclaimable kernel allocations") along with __GFP_RECLAIMABLE. It's
primary motivation was to allow users to tell that an allocation is
short lived and so the allocator can try to place such allocations close
together and prevent long term fragmentation. As much as this sounds
like a reasonable semantic it becomes much less clear when to use the
highlevel GFP_TEMPORARY allocation flag. How long is temporary? Can the
context holding that memory sleep? Can it take locks? It seems there is
no good answer for those questions.
The current implementation of GFP_TEMPORARY is basically GFP_KERNEL |
__GFP_RECLAIMABLE which in itself is tricky because basically none of
the existing caller provide a way to reclaim the allocated memory. So
this is rather misleading and hard to evaluate for any benefits.
I have checked some random users and none of them has added the flag
with a specific justification. I suspect most of them just copied from
other existing users and others just thought it might be a good idea to
use without any measuring. This suggests that GFP_TEMPORARY just
motivates for cargo cult usage without any reasoning.
I believe that our gfp flags are quite complex already and especially
those with highlevel semantic should be clearly defined to prevent from
confusion and abuse. Therefore I propose dropping GFP_TEMPORARY and
replace all existing users to simply use GFP_KERNEL. Please note that
SLAB users with shrinkers will still get __GFP_RECLAIMABLE heuristic and
so they will be placed properly for memory fragmentation prevention.
I can see reasons we might want some gfp flag to reflect shorterm
allocations but I propose starting from a clear semantic definition and
only then add users with proper justification.
This was been brought up before LSF this year by Matthew [1] and it
turned out that GFP_TEMPORARY really doesn't have a clear semantic. It
seems to be a heuristic without any measured advantage for most (if not
all) its current users. The follow up discussion has revealed that
opinions on what might be temporary allocation differ a lot between
developers. So rather than trying to tweak existing users into a
semantic which they haven't expected I propose to simply remove the flag
and start from scratch if we really need a semantic for short term
allocations.
[1] http://lkml.kernel.org/r/20170118054945.GD18349@bombadil.infradead.org
[akpm@linux-foundation.org: fix typo]
[akpm@linux-foundation.org: coding-style fixes]
[sfr@canb.auug.org.au: drm/i915: fix up]
Link: http://lkml.kernel.org/r/20170816144703.378d4f4d@canb.auug.org.au
Link: http://lkml.kernel.org/r/20170728091904.14627-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Neil Brown <neilb@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
855 lines
21 KiB
C
855 lines
21 KiB
C
#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/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)
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{
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struct file *exe_file;
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char *pathbuf, *path;
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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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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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{
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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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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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++pat_ptr;
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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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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 */
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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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case 'E':
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err = cn_print_exe_file(cn);
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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_sem. 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_sem
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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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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:
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atomic_set(&core_state->nr_threads, nr);
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return nr;
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}
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static int coredump_wait(int exit_code, struct core_state *core_state)
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{
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struct task_struct *tsk = current;
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struct mm_struct *mm = tsk->mm;
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int core_waiters = -EBUSY;
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init_completion(&core_state->startup);
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core_state->dumper.task = tsk;
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core_state->dumper.next = NULL;
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if (down_write_killable(&mm->mmap_sem))
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return -EINTR;
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if (!mm->core_state)
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core_waiters = zap_threads(tsk, mm, core_state, exit_code);
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up_write(&mm->mmap_sem);
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if (core_waiters > 0) {
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struct core_thread *ptr;
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freezer_do_not_count();
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wait_for_completion(&core_state->startup);
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freezer_count();
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/*
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* Wait for all the threads to become inactive, so that
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* all the thread context (extended register state, like
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* fpu etc) gets copied to the memory.
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*/
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ptr = core_state->dumper.next;
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while (ptr != NULL) {
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wait_task_inactive(ptr->task, 0);
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ptr = ptr->next;
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}
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}
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return core_waiters;
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}
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static void coredump_finish(struct mm_struct *mm, bool core_dumped)
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{
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struct core_thread *curr, *next;
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struct task_struct *task;
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spin_lock_irq(¤t->sighand->siglock);
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if (core_dumped && !__fatal_signal_pending(current))
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current->signal->group_exit_code |= 0x80;
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current->signal->group_exit_task = NULL;
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current->signal->flags = SIGNAL_GROUP_EXIT;
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spin_unlock_irq(¤t->sighand->siglock);
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next = mm->core_state->dumper.next;
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while ((curr = next) != NULL) {
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next = curr->next;
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task = curr->task;
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/*
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* see exit_mm(), curr->task must not see
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* ->task == NULL before we read ->next.
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*/
|
|
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->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->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 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;
|
|
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);
|
|
|
|
if (ispipe) {
|
|
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 = argv_split(GFP_KERNEL, cn.corename, NULL);
|
|
if (!helper_argv) {
|
|
printk(KERN_WARNING "%s failed to allocate memory\n",
|
|
__func__);
|
|
goto fail_dropcount;
|
|
}
|
|
|
|
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);
|
|
|
|
argv_free(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) {
|
|
mm_segment_t old_fs;
|
|
|
|
old_fs = get_fs();
|
|
set_fs(KERNEL_DS);
|
|
/*
|
|
* If it doesn't exist, that's fine. If there's some
|
|
* other problem, we'll catch it at the filp_open().
|
|
*/
|
|
(void) sys_unlink((const char __user *)cn.corename);
|
|
set_fs(old_fs);
|
|
}
|
|
|
|
/*
|
|
* 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()) {
|
|
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(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;
|
|
while (nr) {
|
|
if (dump_interrupted())
|
|
return 0;
|
|
n = __kernel_write(file, addr, nr, &pos);
|
|
if (n <= 0)
|
|
return 0;
|
|
file->f_pos = pos;
|
|
cprm->written += n;
|
|
cprm->pos += n;
|
|
nr -= 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);
|
|
|
|
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);
|