[FFmpeg-devel] [PATCH 1/2] avcodec/eac3dec: avoid float noise in fixed mode addition to overflow

[Michael Niedermayer]

Fixes: 2.28595e+09 is outside the range of representable values of type 'int'
Fixes: 54644/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AC3_FIXED_fuzzer-4816961584627712

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/ac3.h     | 2 ++
 libavcodec/eac3dec.c | 4 +++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/libavcodec/ac3.h b/libavcodec/ac3.h
index 24304caa61..2386c15ad0 100644
--- a/libavcodec/ac3.h
+++ b/libavcodec/ac3.h
@@ -53,6 +53,7 @@
 #define AC3_DYNAMIC_RANGE1      0
 
 typedef int                     INTFLOAT;
+typedef unsigned int            UINTFLOAT;
 typedef int16_t                 SHORTFLOAT;
 
 #else /* USE_FIXED */
@@ -73,6 +74,7 @@ typedef int16_t                 SHORTFLOAT;
 #define AC3_DYNAMIC_RANGE1      1.0f
 
 typedef float                   INTFLOAT;
+typedef float                   UINTFLOAT;
 typedef float                   SHORTFLOAT;
 
 #endif /* USE_FIXED */
diff --git a/libavcodec/eac3dec.c b/libavcodec/eac3dec.c
index d360b02691..deca51dd3d 100644
--- a/libavcodec/eac3dec.c
+++ b/libavcodec/eac3dec.c
@@ -138,9 +138,11 @@ static void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)
             // spx_noise_blend and spx_signal_blend are both FP.23
             nscale *= 1.0 / (1<<23);
             sscale *= 1.0 / (1<<23);
+            if (nscale < -1.0)
+                nscale = -1.0;
 #endif
             for (i = 0; i < s->spx_band_sizes[bnd]; i++) {
-                float noise  = nscale * (int32_t)av_lfg_get(&s->dith_state);
+                UINTFLOAT noise = (INTFLOAT)(nscale * (int32_t)av_lfg_get(&s->dith_state));
                 s->transform_coeffs[ch][bin]   *= sscale;
                 s->transform_coeffs[ch][bin++] += noise;
             }
-- 
2.17.1