path: root/kernel/fork.c
diff options
authorSukadev Bhattiprolu <>2009-04-02 16:58:08 -0700
committerLinus Torvalds <>2009-04-02 19:04:58 -0700
commitb3bfa0cba867f23365b81658b47efd906830879b (patch)
treee54d9a9c4c23fc00bb2ff3ed57ef5317a0660ea5 /kernel/fork.c
parente4da026f980df125a4918c3bb9fe93185c7ef12a (diff)
signals: protect cinit from blocked fatal signals
Normally SIG_DFL signals to global and container-init are dropped early. But if a signal is blocked when it is posted, we cannot drop the signal since the receiver may install a handler before unblocking the signal. Once this signal is queued however, the receiver container-init has no way of knowing if the signal was sent from an ancestor or descendant namespace. This patch ensures that contianer-init drops all SIG_DFL signals in get_signal_to_deliver() except SIGKILL/SIGSTOP. If SIGSTOP/SIGKILL originate from a descendant of container-init they are never queued (i.e dropped in sig_ignored() in an earler patch). If SIGSTOP/SIGKILL originate from parent namespace, the signal is queued and container-init processes the signal. IOW, if get_signal_to_deliver() sees a sig_kernel_only() signal for global or container-init, the signal must have been generated internally or must have come from an ancestor ns and we process the signal. Further, the signal_group_exit() check was needed to cover the case of a multi-threaded init sending SIGKILL to other threads when doing an exit() or exec(). But since the new sig_kernel_only() check covers the SIGKILL, the signal_group_exit() check is no longer needed and can be removed. Finally, now that we have all pieces in place, set SIGNAL_UNKILLABLE for container-inits. Signed-off-by: Sukadev Bhattiprolu <> Cc: Oleg Nesterov <> Cc: Roland McGrath <> Cc: "Eric W. Biederman" <> Cc: Daniel Lezcano <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'kernel/fork.c')
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index d7eb727eb535..adbea16ec649 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -841,6 +841,8 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
atomic_set(&sig->live, 1);
sig->flags = 0;
+ if (clone_flags & CLONE_NEWPID)
+ sig->flags |= SIGNAL_UNKILLABLE;
sig->group_exit_code = 0;
sig->group_exit_task = NULL;
sig->group_stop_count = 0;