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>

diff --git a/kernel/marker.c b/kernel/marker.c
index 50effc0..48a4ea5 100644 (file)
--- 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;