[FFmpeg-devel] [PATCH 2/2] avcodec/aacdec_fixed: fix invalid shift in predict()

[Michael Niedermayer]

Fixes: runtime error: shift exponent -2 is negative
Fixes: 2818/clusterfuzz-testcase-minimized-5062943676825600

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavcodec/aacdec_fixed.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/libavcodec/aacdec_fixed.c b/libavcodec/aacdec_fixed.c
index ccfef7f652..f6a533010f 100644
--- a/libavcodec/aacdec_fixed.c
+++ b/libavcodec/aacdec_fixed.c
@@ -305,8 +305,12 @@ static av_always_inline void predict(PredictorState *ps, int *coef,
     if (output_enable) {
         int shift = 28 - pv.exp;
 
-        if (shift < 31)
-            *coef += (pv.mant + (1 << (shift - 1))) >> shift;
+        if (shift < 31) {
+            if (shift > 0) {
+                *coef += (pv.mant + (1 << (shift - 1))) >> shift;
+            } else
+                *coef += pv.mant << -shift;
+        }
     }
 
     e0 = av_int2sf(*coef, 2);
-- 
2.13.0