mxfdec: check index_tables before dereferencing in close.

Fixes null pointer dereference

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 6 insertions, 4 deletions

diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index 06bca10c03..921dc427a3 100644
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -2250,10 +2250,12 @@ static int mxf_read_close(AVFormatContext *s)
     av_freep(&mxf->aesc);
     av_freep(&mxf->local_tags);
 
-    for (i = 0; i < mxf->nb_index_tables; i++) {
-        av_freep(&mxf->index_tables[i].segments);
-        av_freep(&mxf->index_tables[i].ptses);
-        av_freep(&mxf->index_tables[i].fake_index);
+    if (mxf->index_tables) {
+        for (i = 0; i < mxf->nb_index_tables; i++) {
+            av_freep(&mxf->index_tables[i].segments);
+            av_freep(&mxf->index_tables[i].ptses);
+            av_freep(&mxf->index_tables[i].fake_index);
+        }
     }
     av_freep(&mxf->index_tables);