Commit 86989c41 authored Jul 19, 2018 by Eric W. Biederman

signal: Always ignore SIGKILL and SIGSTOP sent to the global init



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>

parent 5b394b2d

kernel/signal.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -78,6 +78,10 @@ static bool 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 true;

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