flac: fix infinite loops on all-zero input or end-of-stream.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

1 files changed, 9 insertions, 0 deletions

diff --git a/libavcodec/flacdec.c b/libavcodec/flacdec.c
index 2b7f7eeb9e..7454d8b7f7 100644
--- a/libavcodec/flacdec.c
+++ b/libavcodec/flacdec.c
@@ -422,7 +422,16 @@ static inline int decode_subframe(FLACContext *s, int channel)
     type = get_bits(&s->gb, 6);
 
     if (get_bits1(&s->gb)) {
+        int left = get_bits_left(&s->gb);
         wasted = 1;
+        if ( left < 0 ||
+            (left < s->curr_bps && !show_bits_long(&s->gb, left)) ||
+                                   !show_bits_long(&s->gb, s->curr_bps)) {
+            av_log(s->avctx, AV_LOG_ERROR,
+                   "Invalid number of wasted bits > available bits (%d) - left=%d\n",
+                   s->curr_bps, left);
+            return AVERROR_INVALIDDATA;
+        }
         while (!get_bits1(&s->gb))
             wasted++;
         s->curr_bps -= wasted;