[FFmpeg-cvslog] alsdec: validate time diff index

[Andreas Cadhalpun]

ffmpeg | branch: master | Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com> | Sat Apr 18 20:09:28 2015 +0200| [faf9fe2c224ea81a98afd53e2f0be0a2e13aeca9] | committer: Michael Niedermayer

alsdec: validate time diff index

If begin is smaller than t, the subtraction 'begin -= t' wraps around,
because begin is unsigned. The same applies for end < t.

This causes segmentation faults.

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=faf9fe2c224ea81a98afd53e2f0be0a2e13aeca9
---

 libavcodec/alsdec.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
index 787792f..7c652af 100644
--- a/libavcodec/alsdec.c
+++ b/libavcodec/alsdec.c
@@ -1290,8 +1290,16 @@ static int revert_channel_correlation(ALSDecContext *ctx, ALSBlockData *bd,
 
             if (ch[dep].time_diff_sign) {
                 t      = -t;
+                if (t > 0 && begin < t) {
+                    av_log(ctx->avctx, AV_LOG_ERROR, "begin %u smaller than time diff index %d.\n", begin, t);
+                    return AVERROR_INVALIDDATA;
+                }
                 begin -= t;
             } else {
+                if (t > 0 && end < t) {
+                    av_log(ctx->avctx, AV_LOG_ERROR, "end %u smaller than time diff index %d.\n", end, t);
+                    return AVERROR_INVALIDDATA;
+                }
                 end   -= t;
             }