[FFmpeg-devel] [PATCH] avcodec/bonk: Avoid undefined integer overflow in predictor_calc_error()

[FFmpeg-devel] [PATCH] avcodec/bonk: Avoid undefined integer overflow in predictor_calc_error()

[Michael Niedermayer]

Fixes: signed integer overflow: -159584 * 5105950 cannot be represented in type 'int'
Fixes: 55165/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_BONK_fuzzer-5796023719297024

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/bonk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/bonk.c b/libavcodec/bonk.c
index 5f510e49103..f2baa9c9315 100644
--- a/libavcodec/bonk.c
+++ b/libavcodec/bonk.c
@@ -265,14 +265,14 @@ static inline int shift(int a, int b)
 
 static int predictor_calc_error(int *k, int *state, int order, int error)
 {
-    int i, x = error - shift_down(k[order-1] * state[order-1], LATTICE_SHIFT);
+    int i, x = error - shift_down(k[order-1] * (unsigned)state[order-1], LATTICE_SHIFT);
     int *k_ptr = &(k[order-2]),
         *state_ptr = &(state[order-2]);
 
     for (i = order-2; i >= 0; i--, k_ptr--, state_ptr--) {
         unsigned k_value = *k_ptr, state_value = *state_ptr;
 
-        x -= shift_down(k_value * state_value, LATTICE_SHIFT);
+        x -= shift_down(k_value * (unsigned)state_value, LATTICE_SHIFT);
         state_ptr[1] = state_value + shift_down(k_value * x, LATTICE_SHIFT);
     }
 
-- 
2.17.1

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Re: [FFmpeg-devel] [PATCH] avcodec/bonk: Avoid undefined integer overflow in predictor_calc_error()

[Michael Niedermayer]

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On Sat, Apr 22, 2023 at 11:25:55PM +0200, Michael Niedermayer wrote:
> Fixes: signed integer overflow: -159584 * 5105950 cannot be represented in type 'int'
> Fixes: 55165/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_BONK_fuzzer-5796023719297024
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/bonk.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

will apply

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Observe your enemies, for they first find out your faults. -- Antisthenes

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