[FFmpeg-devel] [PATCH 29/30] avformat/matroskaenc: Check BlockAdditional size before use

Andreas Rheinhardt andreas.rheinhardt at gmail.com
Sun Jan 26 07:10:27 EET 2020


Don't read a 64bit number before having checked that the data is at
least 8 bytes long.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavformat/matroskaenc.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 444032b431..8fc672a31f 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -2100,9 +2100,13 @@ static void mkv_write_block(AVFormatContext *s, AVIOContext *pb,
                                         AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL,
                                         &side_data_size);
     if (side_data) {
-        additional_id = AV_RB64(side_data);
-        side_data += 8;
-        side_data_size -= 8;
+        if (side_data_size < 8) {
+            side_data_size = 0;
+        } else {
+            additional_id   = AV_RB64(side_data);
+            side_data      += 8;
+            side_data_size -= 8;
+        }
     }
 
     if ((side_data_size && additional_id == 1) || discard_padding) {
-- 
2.20.1



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