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authorOleg Nesterov <oleg@redhat.com>2013-04-30 15:28:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-30 17:04:06 -0700
commit6cd8f0acae3420afce37bf51a9ff8c2c20342af5 (patch)
tree38478d4eb5b1c2d911c865c088a79edf2ebcea77 /fs
parent403bad72b67d8b3f5a0240af5023adfa48132a65 (diff)
downloadlinux-6cd8f0acae3420afce37bf51a9ff8c2c20342af5.tar.gz
coredump: ensure that SIGKILL always kills the dumping thread
prepare_signal() blesses SIGKILL sent to the dumping process but this signal can be "lost" anyway. The problems is, complete_signal() sees SIGNAL_GROUP_EXIT and skips the "kill them all" logic. And even if the dumping process is single-threaded (so the target is always "correct"), the group-wide SIGKILL is not recorded in task->pending and thus __fatal_signal_pending() won't be true. A multi-threaded case has even more problems. And even ignoring all technical details, SIGNAL_GROUP_EXIT doesn't look right to me. This coredumping process is not exiting yet, it can do a lot of work dumping the core. With this patch the dumping process doesn't have SIGNAL_GROUP_EXIT, we set signal->group_exit_task instead. This makes signal_group_exit() true and thus this should equally close the races with exit/exec/stop but allows to kill the dumping thread reliably. Notes: - It is not clear what should we do with ->group_exit_code if the dumper was killed, see the next change. - we need more (hopefully straightforward) changes to ensure that SIGKILL actually interrupts the coredump. Basically we need to check __fatal_signal_pending() in dump_write() and dump_seek(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Tested-by: Mandeep Singh Baines <msb@chromium.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Neil Horman <nhorman@redhat.com> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Roland McGrath <roland@hack.frob.com> Cc: Tejun Heo <tj@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/coredump.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/fs/coredump.c b/fs/coredump.c
index f91cfd8cd5f..6fea5904353 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -263,7 +263,6 @@ static int zap_process(struct task_struct *start, int exit_code)
struct task_struct *t;
int nr = 0;
- start->signal->flags = SIGNAL_GROUP_EXIT;
start->signal->group_exit_code = exit_code;
start->signal->group_stop_count = 0;
@@ -291,8 +290,9 @@ static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
if (!signal_group_exit(tsk->signal)) {
mm->core_state = core_state;
nr = zap_process(tsk, exit_code);
+ tsk->signal->group_exit_task = tsk;
/* ignore all signals except SIGKILL, see prepare_signal() */
- tsk->signal->flags |= SIGNAL_GROUP_COREDUMP;
+ tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
}
spin_unlock_irq(&tsk->sighand->siglock);
@@ -343,6 +343,7 @@ static int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
if (unlikely(p->mm == mm)) {
lock_task_sighand(p, &flags);
nr += zap_process(p, exit_code);
+ p->signal->flags = SIGNAL_GROUP_EXIT;
unlock_task_sighand(p, &flags);
}
break;
@@ -394,6 +395,11 @@ static void coredump_finish(struct mm_struct *mm)
struct core_thread *curr, *next;
struct task_struct *task;
+ spin_lock_irq(&current->sighand->siglock);
+ current->signal->group_exit_task = NULL;
+ current->signal->flags = SIGNAL_GROUP_EXIT;
+ spin_unlock_irq(&current->sighand->siglock);
+
next = mm->core_state->dumper.next;
while ((curr = next) != NULL) {
next = curr->next;