From: Eric W. Biederman ebiederm@xmission.com
[ Upstream commit 86989c41b5ea08776c450cb759592532314a4ed6 ]
If the first process started (aka /sbin/init) receives a SIGKILL it will panic the system if it is delivered. Making the system unusable and undebugable. It isn't much better if the first process started receives SIGSTOP.
So always ignore SIGSTOP and SIGKILL sent to init.
This is done in a separate clause in sig_task_ignored as force_sig_info can clear SIG_UNKILLABLE and this protection should work even then.
Reviewed-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/signal.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/kernel/signal.c b/kernel/signal.c index 2bb1f9dc86c7d..30914b3c76b21 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -71,6 +71,10 @@ static int sig_task_ignored(struct task_struct *t, int sig, bool force)
handler = sig_handler(t, sig);
+ /* SIGKILL and SIGSTOP may not be sent to the global init */ + if (unlikely(is_global_init(t) && sig_kernel_only(sig))) + return true; + if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) && handler == SIG_DFL && !(force && sig_kernel_only(sig))) return 1;