Re: [FFmpeg-devel] [PATCH] avcodec/pixlet: Simplify nbits computation

[Paul B Mahol]

On 7/27/17, Michael Niedermayer  wrote:
> Fixes multiple integer overflows
> Fixes: runtime error: signed integer overflow: 1 + 2147483647 cannot be
> represented in type 'int'
>
> Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer 
> ---
>  libavcodec/pixlet.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

LGTM
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[FFmpeg-devel] [PATCH] avcodec/pixlet: Simplify nbits computation

[Michael Niedermayer]

Fixes multiple integer overflows
Fixes: runtime error: signed integer overflow: 1 + 2147483647 cannot be 
represented in type 'int'

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

diff --git a/libavcodec/pixlet.c b/libavcodec/pixlet.c
index 0e541a9ccb..a9661d3ab6 100644
--- a/libavcodec/pixlet.c
+++ b/libavcodec/pixlet.c
@@ -206,8 +206,8 @@ static int read_high_coeffs(AVCodecContext *avctx, uint8_t 
*src, int16_t *dst, i
 if ((ret = init_get_bits8(b, src, bytestream2_get_bytes_left(>gb))) < 
0)
   return ret;
 
-if ((a >= 0) + (a ^ (a >> 31)) - (a >> 31) != 1) {
-nbits = 33 - ff_clz((a >= 0) + (a ^ (a >> 31)) - (a >> 31) - 1);
+if (a ^ (a >> 31)) {
+nbits = 33 - ff_clz(a ^ (a >> 31));
 if (nbits > 16)
 return AVERROR_INVALIDDATA;
 } else {
-- 
2.13.0

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