tracepoint: Fix use of tracepoint funcs after rcu free
Commit de7b2973903c "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: de7b2973903c "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>
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index ac5b23c..6620e58 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -188,7 +188,6 @@
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 @@
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 @@
WARN_ON_ONCE(1);
return PTR_ERR(old);
}
- release_probes(old);
if (!tp_funcs) {
/* Removed last function */
@@ -232,6 +231,7 @@
static_key_slow_dec(&tp->key);
}
rcu_assign_pointer(tp->funcs, tp_funcs);
+ release_probes(old);
return 0;
}
