[FFmpeg-devel] [PATCH] pngdec: check if previous frame exists instead of trusting sequence_number

[Andreas Cadhalpun]

This fixes a segmentation fault caused by calling memcpy with NULL as
second argument in handle_p_frame_apng.

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
---
 libavcodec/pngdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index 36275ae..a7b330b 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -922,7 +922,7 @@ static int decode_fctl_chunk(AVCodecContext *avctx, PNGDecContext *s,
         return AVERROR_INVALIDDATA;
     }
 
-    if (sequence_number == 0 && dispose_op == APNG_DISPOSE_OP_PREVIOUS) {
+    if (!s->previous_picture.f->data[0] && dispose_op == APNG_DISPOSE_OP_PREVIOUS) {
         // No previous frame to revert to for the first frame
         // Spec says to just treat it as a APNG_DISPOSE_OP_BACKGROUND
         dispose_op = APNG_DISPOSE_OP_BACKGROUND;
-- 
2.10.2