tracing/kprobes: unregister_trace_probe needs to be called under mutex

Comment in unregister_trace_probe() says probe_lock will be held when it
gets called. However there is a case where it might called without the
probe_lock being held. Also since we are traversing the probe_list and
deleting an element from the probe_list, probe_lock should be held.

This was first pointed in uprobes traceevent review by Frederic
Weisbecker here.  (http://lkml.org/lkml/2010/5/12/106)

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20100630084548.GA10325@linux.vnet.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 1b79d1c15726..8b27c9849b42 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -925,14 +925,17 @@ static int create_trace_probe(int argc, char **argv)
                         pr_info("Delete command needs an event name.\n");
                         return -EINVAL;
                 }
+                mutex_lock(&probe_lock);
                 tp = find_probe_event(event, group);
                 if (!tp) {
+                        mutex_unlock(&probe_lock);
                         pr_info("Event %s/%s doesn't exist.\n", group, event);
                         return -ENOENT;
                 }
                 /* delete an event */
                 unregister_trace_probe(tp);
                 free_trace_probe(tp);
+                mutex_unlock(&probe_lock);
                 return 0;
         }