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Commit 921cf9f6 authored by Sukadev Bhattiprolu's avatar Sukadev Bhattiprolu Committed by Linus Torvalds
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signals: protect cinit from unblocked SIG_DFL signals 



Drop early any SIG_DFL or SIG_IGN signals to container-init from within
the same container.  But queue SIGSTOP and SIGKILL to the container-init
if they are from an ancestor container.

Blocked, fatal signals (i.e when SIG_DFL is to terminate) from within the
container can still terminate the container-init.  That will be addressed
in the next patch.

Note:	To be bisect-safe, SIGNAL_UNKILLABLE will be set for container-inits
   	in a follow-on patch. Until then, this patch is just a preparatory
	step.

Signed-off-by: default avatarSukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7978b567

kernel/signal.c

+19 −9
Original line number Diff line number Diff line
@@ -55,20 +55,21 @@ static int sig_handler_ignored(void __user *handler, int sig) 
		(handler == SIG_DFL && sig_kernel_ignore(sig));

}



static int sig_task_ignored(struct task_struct *t, int sig)

static int sig_task_ignored(struct task_struct *t, int sig,

		int from_ancestor_ns)

{

	void __user *handler;



	handler = sig_handler(t, sig);



	if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&

			handler == SIG_DFL)

			handler == SIG_DFL && !from_ancestor_ns)

		return 1;



	return sig_handler_ignored(handler, sig);

}



static int sig_ignored(struct task_struct *t, int sig)

static int sig_ignored(struct task_struct *t, int sig, int from_ancestor_ns)

{

	/*

	 * Blocked signals are never ignored, since the
@@ -78,7 +79,7 @@ static int sig_ignored(struct task_struct *t, int sig) 
	if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))

		return 0;



	if (!sig_task_ignored(t, sig))

	if (!sig_task_ignored(t, sig, from_ancestor_ns))

		return 0;



	/*
@@ -634,7 +635,7 @@ static int check_kill_permission(int sig, struct siginfo *info, 
 * Returns true if the signal should be actually delivered, otherwise

 * it should be dropped.

 */

static int prepare_signal(int sig, struct task_struct *p)

static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)

{

	struct signal_struct *signal = p->signal;

	struct task_struct *t;
@@ -718,7 +719,7 @@ static int prepare_signal(int sig, struct task_struct *p) 
		}

	}



	return !sig_ignored(p, sig);

	return !sig_ignored(p, sig, from_ancestor_ns);

}



/*
@@ -832,7 +833,8 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t, 
	trace_sched_signal_send(sig, t);



	assert_spin_locked(&t->sighand->siglock);

	if (!prepare_signal(sig, t))



	if (!prepare_signal(sig, t, from_ancestor_ns))

		return 0;



	pending = group ? &t->signal->shared_pending : &t->pending;
@@ -902,7 +904,15 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t, 
static int send_signal(int sig, struct siginfo *info, struct task_struct *t,

			int group)

{

	return __send_signal(sig, info, t, group, 0);

	int from_ancestor_ns = 0;



#ifdef CONFIG_PID_NS

	if (!is_si_special(info) && SI_FROMUSER(info) &&

			task_pid_nr_ns(current, task_active_pid_ns(t)) <= 0)

		from_ancestor_ns = 1;

#endif



	return __send_signal(sig, info, t, group, from_ancestor_ns);

}



int print_fatal_signals;
@@ -1336,7 +1346,7 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group) 
		goto ret;



	ret = 1; /* the signal is ignored */

	if (!prepare_signal(sig, t))

	if (!prepare_signal(sig, t, 0))

		goto out;



	ret = 0;