[FFmpeg-cvslog] avcodec/aacdec_fixed: Check s for being too small

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Mon Jun 19 14:04:32 2017 +0200| [cbc4f40d137279eac5cea66f21fc99d1d87ccc37] | committer: Michael Niedermayer

avcodec/aacdec_fixed: Check s for being too small

Fixes: runtime error: shift exponent -8 is negative
Fixes: 2286/clusterfuzz-testcase-minimized-5711764169687040

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit cf7edbd6c5d48d7302877352f7b60092d5b65243)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=cbc4f40d137279eac5cea66f21fc99d1d87ccc37
---

 libavcodec/aacdec_fixed.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libavcodec/aacdec_fixed.c b/libavcodec/aacdec_fixed.c
index a72c1e34da..68db8bdcbd 100644
--- a/libavcodec/aacdec_fixed.c
+++ b/libavcodec/aacdec_fixed.c
@@ -180,14 +180,15 @@ static void subband_scale(int *dst, int *src, int scale, int offset, int len)
             out = (int)(((int64_t)src[i] * c) >> 32);
             dst[i] = ((int)(out+round) >> s) * ssign;
         }
-    }
-    else {
+    } else if (s > -32) {
         s = s + 32;
         round = 1 << (s-1);
         for (i=0; i<len; i++) {
             out = (int)((int64_t)((int64_t)src[i] * c + round) >> s);
             dst[i] = out * (unsigned)ssign;
         }
+    } else {
+        av_log(NULL, AV_LOG_ERROR, "Overflow in subband_scale()\n");
     }
 }