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authorOleg Nesterov <oleg@redhat.com>2012-03-19 20:03:41 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-21 01:16:50 +0400
commitb6e238dceed36891cc633167afe7151f1f3d83c5 (patch)
treeeef4928c1a0cb1b56eb20f8d0ee592709d533f10
parente636825346b36a07ccfc8e30946d52855e21f681 (diff)
downloadlinux-b6e238dceed36891cc633167afe7151f1f3d83c5.tar.xz
exit_signal: fix the "parent has changed security domain" logic
exit_notify() changes ->exit_signal if the parent already did exec. This doesn't really work, we are not going to send the signal now if there is another live thread or the exiting task is traced. The parent can exec before the last dies or the tracer detaches. Move this check into do_notify_parent() which actually sends the signal. The user-visible change is that we do not change ->exit_signal, and thus the exiting task is still "clone children" for do_wait()->eligible_child(__WCLONE). Hopefully this is fine, the current logic is racy anyway. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/exit.c14
-rw-r--r--kernel/signal.c9
2 files changed, 9 insertions, 14 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 51ac4ced1313..ce5f758f40bd 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -818,20 +818,6 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
if (group_dead)
kill_orphaned_pgrp(tsk->group_leader, NULL);
- /* Let father know we died
- *
- * Thread signals are configurable, but you aren't going to use
- * that to send signals to arbitrary processes.
- * That stops right now.
- *
- * If the parent exec id doesn't match the exec id we saved
- * when we started then we know the parent has changed security
- * domain.
- */
- if (thread_group_leader(tsk) && tsk->exit_signal != SIGCHLD &&
- tsk->parent_exec_id != tsk->real_parent->self_exec_id)
- tsk->exit_signal = SIGCHLD;
-
if (unlikely(tsk->ptrace)) {
int sig = thread_group_leader(tsk) &&
thread_group_empty(tsk) &&
diff --git a/kernel/signal.c b/kernel/signal.c
index 8511e39813c7..e76001ccf5cd 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1652,6 +1652,15 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
BUG_ON(!tsk->ptrace &&
(tsk->group_leader != tsk || !thread_group_empty(tsk)));
+ if (sig != SIGCHLD) {
+ /*
+ * This is only possible if parent == real_parent.
+ * Check if it has changed security domain.
+ */
+ if (tsk->parent_exec_id != tsk->parent->self_exec_id)
+ sig = SIGCHLD;
+ }
+
info.si_signo = sig;
info.si_errno = 0;
/*