avcodec/atrac9dec: Check grad_range[1] more tightly

Alternatively the array could be made bigger but the extra values
would not be read without other changes.

Fixes: Out of array access
Fixes: 15658/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ATRAC9_fuzzer-5738260074070016
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/atrac9dec.c b/libavcodec/atrac9dec.c
index 7e59af8b6dcbf40058f845d0906efd0451d9a2d8..4ea6ff0f315653ef93ee6834611ed65f7459eb7b 100644 (file)
--- a/libavcodec/atrac9dec.c
+++ b/libavcodec/atrac9dec.c
@@ -121,7 +121,7 @@ static inline int parse_gradient(ATRAC9Context *s, ATRAC9BlockData *b,
     }
     b->grad_boundary = get_bits(gb, 4);
 
-    if (grad_range[0] >= grad_range[1] || grad_range[1] > 47)
+    if (grad_range[0] >= grad_range[1] || grad_range[1] > 31)
         return AVERROR_INVALIDDATA;
 
     if (b->grad_boundary > b->q_unit_cnt)