Commit 8058bd0f authored May 08, 2014 by Mathieu Desnoyers Committed by Steven Rostedt May 08, 2014

tracepoint: Fix use of tracepoint funcs after rcu free

Commit de7b2973 "tracepoint: Use struct pointer instead of name hash
for reg/unreg tracepoints" introduces a use after free by calling
release_probes on the old struct tracepoint array before the newly
allocated array is published with rcu_assign_pointer. There is a race
window where tracepoints (RCU readers) can perform a
"use-after-grace-period-after-free", which shows up as a GPF in
stress-tests.

Link: http://lkml.kernel.org/r/53698021.5020108@oracle.com
Link: http://lkml.kernel.org/p/1399549669-25465-1-git-send-email-mathieu.desnoyers@efficios.com



Reported-by: Sasha Levin <sasha.levin@oracle.com>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Dave Jones <davej@redhat.com>
Fixes: de7b2973 "tracepoint: Use struct pointer instead of name hash for reg/unreg tracepoints"
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

parent 098507ae

kernel/tracepoint.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -188,7 +188,6 @@ static int tracepoint_add_func(struct tracepoint *tp,
		WARN_ON_ONCE(1);
		return PTR_ERR(old);
		}
		release_probes(old);

		/*
		* rcu_assign_pointer has a smp_wmb() which makes sure that the new
		@@ -200,6 +199,7 @@ static int tracepoint_add_func(struct tracepoint *tp,
		rcu_assign_pointer(tp->funcs, tp_funcs);
		if (!static_key_enabled(&tp->key))
		static_key_slow_inc(&tp->key);
		release_probes(old);
		return 0;
		}

		@@ -221,7 +221,6 @@ static int tracepoint_remove_func(struct tracepoint *tp,
		WARN_ON_ONCE(1);
		return PTR_ERR(old);
		}
		release_probes(old);

		if (!tp_funcs) {
		/* Removed last function */
		@@ -232,6 +231,7 @@ static int tracepoint_remove_func(struct tracepoint *tp,
		static_key_slow_dec(&tp->key);
		}
		rcu_assign_pointer(tp->funcs, tp_funcs);
		release_probes(old);
		return 0;
		}