[FFmpeg-cvslog] lagarith: check count before writing zeros.

[Michael Niedermayer]

ffmpeg | branch: release/0.8 | Michael Niedermayer <michaelni at gmx.at> | Sat Apr 14 18:28:31 2012 +0200| [44da556815fc02ed0c763e8e8bda3ea7824b7954] | committer: Reinhard Tartler

lagarith: check count before writing zeros.

Fixes CVE-2012-2793

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Anton Khirnov <anton at khirnov.net>
(cherry picked from commit b631e4ed64f7d1b9ca8f897fda31140e8d1fad81)

Signed-off-by: Reinhard Tartler <siretart at tauware.de>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=44da556815fc02ed0c763e8e8bda3ea7824b7954
---

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

diff --git a/libavcodec/lagarith.c b/libavcodec/lagarith.c
index 3d53536..5e00a75 100644
--- a/libavcodec/lagarith.c
+++ b/libavcodec/lagarith.c
@@ -322,6 +322,11 @@ static int lag_decode_zero_run_line(LagarithContext *l, uint8_t *dst,
 output_zeros:
     if (l->zeros_rem) {
         count = FFMIN(l->zeros_rem, width - i);
+        if (end - dst < count) {
+            av_log(l->avctx, AV_LOG_ERROR, "Too many zeros remaining.\n");
+            return AVERROR_INVALIDDATA;
+        }
+
         memset(dst, 0, count);
         l->zeros_rem -= count;
         dst += count;