[Qemu-trivial] [PATCH] block/qcow2-snapshot: Fix a null pointer dereference in qcow2_free_snapshots

[Hu Chaojian]

From: chaojianhu <address@hidden>

In function qcow2_do_open, if "go fail;" before calling qcow2_read_snapshots, 
then snapshots 
will always be NULL. When dealing with "fail:", qcow2_free_snapshots will be 
called, and 
s->snapshots will be dereferenced without checked.

Reported-by: chaojianhu <address@hidden>
Signed-off-by: chaojianhu <address@hidden>

---
 block/qcow2-snapshot.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 44243e0..4a8128c 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -35,6 +35,10 @@ void qcow2_free_snapshots(BlockDriverState *bs)
     BDRVQcow2State *s = bs->opaque;
     int i;
 
+    if (NULL == s->snapshots) {
+        return;
+    }
+
     for(i = 0; i < s->nb_snapshots; i++) {
         g_free(s->snapshots[i].name);
         g_free(s->snapshots[i].id_str);
-- 
1.9.1