[FFmpeg-cvslog] mp3dec: Fix possibly exploitable crash

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Fri Sep 28 01:38:44 2012 +0200| [94041febc53a6da10e34c2bfff9ff1d580fdce60] | committer: Michael Niedermayer

mp3dec: Fix possibly exploitable crash

I was sadly unable to find a non fuzzed mp3 that uses the
feature that contained the bug (and i searched hard ...), thus
while this fixes the security issue. It may or may not fix
mixed blocks in 8khz mp3s, i cant say due to lack of samples to test.

Security issue exists since: b37d945dd4213cb8e92146571b0374cd45d52286

Reported-by: Dale Curtis <dalecurtis at google.com>
(Probably) Found-by: inferno at chromium.org
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=94041febc53a6da10e34c2bfff9ff1d580fdce60
---

 libavcodec/mpegaudiodec.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/mpegaudiodec.c b/libavcodec/mpegaudiodec.c
index 2393da7..d6de1f7 100644
--- a/libavcodec/mpegaudiodec.c
+++ b/libavcodec/mpegaudiodec.c
@@ -213,7 +213,7 @@ static void ff_compute_band_indexes(MPADecodeContext *s, GranuleDef *g)
             else
                 g->long_end = 6;
 
-            g->short_start = 2 + (s->sample_rate_index != 8);
+            g->short_start = 3;
         } else {
             g->long_end    = 0;
             g->short_start = 0;