[FFmpeg-cvslog] alsdec: check block length

[Reinhard Tartler]

ffmpeg | branch: master | Reinhard Tartler <siretart at tauware.de> | Sun Dec  8 13:24:26 2013 -0500| [2a0fb7286d67c47e44aa76c237ede117b22af616] | committer: Reinhard Tartler

alsdec: check block length

Fix writing over the end

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Addresses: CVE-2013-0845

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2a0fb7286d67c47e44aa76c237ede117b22af616
---

 libavcodec/alsdec.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
index 782a1b8..f7dee7d 100644
--- a/libavcodec/alsdec.c
+++ b/libavcodec/alsdec.c
@@ -1376,6 +1376,11 @@ static int read_frame_data(ALSDecContext *ctx, unsigned int ra_frame)
 
         for (b = 0; b < ctx->num_blocks; b++) {
             bd.block_length = div_blocks[b];
+            if (bd.block_length <= 0) {
+                av_log(ctx->avctx, AV_LOG_WARNING,
+                       "Invalid block length %d in channel data!\n", bd.block_length);
+                continue;
+            }
 
             for (c = 0; c < avctx->channels; c++) {
                 bd.const_block = ctx->const_block + c;