markers: don't risk NULL deref in marker

get_marker() may return NULL, so test for it.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 4 deletions

diff --git a/kernel/marker.c b/kernel/marker.c
index 50effc01d9a2..48a4ea5afffd 100644
--- a/kernel/marker.c
+++ b/kernel/marker.c
@@ -698,14 +698,12 @@ int marker_probe_unregister(const char *name,
 {
         struct marker_entry *entry;
         struct marker_probe_closure *old;
-        int ret = 0;
+        int ret = -ENOENT;
 
         mutex_lock(&markers_mutex);
         entry = get_marker(name);
-        if (!entry) {
-                ret = -ENOENT;
+        if (!entry)
                 goto end;
-        }
         if (entry->rcu_pending)
                 rcu_barrier();
         old = marker_entry_remove_probe(entry, probe, probe_private);
@@ -713,12 +711,15 @@ int marker_probe_unregister(const char *name,
         marker_update_probes();         /* may update entry */
         mutex_lock(&markers_mutex);
         entry = get_marker(name);
+        if (!entry)
+                goto end;
         entry->oldptr = old;
         entry->rcu_pending = 1;
         /* write rcu_pending before calling the RCU callback */
         smp_wmb();
         call_rcu(&entry->rcu, free_old_closure);
         remove_marker(name);    /* Ignore busy error message */
+        ret = 0;
 end:
         mutex_unlock(&markers_mutex);
         return ret;