[FFmpeg-devel] [PATCH 1/3] avcodec/huffyuvdec: avoid undefined behavior with get_vlc2() failure

[FFmpeg-devel] [PATCH 1/3] avcodec/huffyuvdec: avoid undefined behavior with get_vlc2() failure

[Michael Niedermayer]

Fixes: left shift of negative value -1
Fixes: 59889/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HUFFYUV_fuzzer-5472742275940352

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

diff --git a/libavcodec/huffyuvdec.c b/libavcodec/huffyuvdec.c
index 8ba67bbdeb..1a7690da94 100644
--- a/libavcodec/huffyuvdec.c
+++ b/libavcodec/huffyuvdec.c
@@ -755,7 +755,7 @@ static void decode_plane_bitstream(HYuvDecContext *s, int width, int plane)
             }
         }
         if( width&1 && get_bits_left(&s->gb)>0 ) {
-            int dst = get_vlc2(&s->gb, s->vlc[plane].table, VLC_BITS, 3)<<2;
+            int dst = (unsigned)get_vlc2(&s->gb, s->vlc[plane].table, VLC_BITS, 3)<<2;
             s->temp16[0][width-1] = dst + get_bits(&s->gb, 2);
         }
     }
-- 
2.17.1

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[FFmpeg-devel] [PATCH 2/3] tools/target_dec_fuzzer: Adjust threshold for speex

[Michael Niedermayer]

Fixes: Timeout
Fixes: 59731/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SPEEX_fuzzer-4809436670328832

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

diff --git a/tools/target_dec_fuzzer.c b/tools/target_dec_fuzzer.c
index 42de479829..165951dc9d 100644
--- a/tools/target_dec_fuzzer.c
+++ b/tools/target_dec_fuzzer.c
@@ -278,6 +278,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_SCPR:        maxpixels  /= 32;    break;
     case AV_CODEC_ID_SCREENPRESSO:maxpixels  /= 64;    break;
     case AV_CODEC_ID_SIMBIOSIS_IMX:maxpixels /= 16384; break;
+    case AV_CODEC_ID_SPEEX:       maxsamples /= 128;   break;
     case AV_CODEC_ID_SMACKAUDIO:  maxsamples /= 4096;  break;
     case AV_CODEC_ID_SMACKVIDEO:  maxpixels  /= 64;    break;
     case AV_CODEC_ID_SNOW:        maxpixels  /= 128;   break;
-- 
2.17.1

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Re: [FFmpeg-devel] [PATCH 2/3] tools/target_dec_fuzzer: Adjust threshold for speex

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 666 bytes --]

On Tue, Jun 20, 2023 at 01:04:23AM +0200, Michael Niedermayer wrote:
> Fixes: Timeout
> Fixes: 59731/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SPEEX_fuzzer-4809436670328832
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  tools/target_dec_fuzzer.c | 1 +
>  1 file changed, 1 insertion(+)

will apply

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have never wished to cater to the crowd; for what I know they do not
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[FFmpeg-devel] [PATCH 3/3] avutil/softfloat: fix av_sincos_sf()

[Michael Niedermayer]

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavutil/softfloat.h       | 2 +-
 libavutil/tests/softfloat.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavutil/softfloat.h b/libavutil/softfloat.h
index a651406f74..1520027ddc 100644
--- a/libavutil/softfloat.h
+++ b/libavutil/softfloat.h
@@ -281,7 +281,7 @@ static av_unused void av_sincos_sf(int a, int *s, int *c)
                 (int64_t)av_sintbl_4_sf[(idx & 0x1f) + 1] * (a & 0x7ff) +
                 0x400) >> 11);
 
-    *c = (int)(((int64_t)cv * ct + (int64_t)sv * st + 0x20000000) >> 30);
+    *c = (int)(((int64_t)cv * ct - (int64_t)sv * st + 0x20000000) >> 30);
 
     *s = (int)(((int64_t)cv * st + (int64_t)sv * ct + 0x20000000) >> 30);
 }
diff --git a/libavutil/tests/softfloat.c b/libavutil/tests/softfloat.c
index c06de44933..a2e628fe81 100644
--- a/libavutil/tests/softfloat.c
+++ b/libavutil/tests/softfloat.c
@@ -148,7 +148,7 @@ int main(void){
         av_sincos_sf(i*(1ULL<<32)/36/4, &s, &c);
         errs = (double)s/ (1<<30) - sin(i*M_PI/36);
         errc = (double)c/ (1<<30) - cos(i*M_PI/36);
-        if (fabs(errs) > 0.00000002 || fabs(errc) >0.001) {
+        if (fabs(errs) > 0.000000004 || fabs(errc) >0.000000004) {
             printf("sincos FAIL %d %f %f %f %f\n", i, (float)s/ (1<<30), (float)c/ (1<<30), sin(i*M_PI/36), cos(i*M_PI/36));
         }
 
-- 
2.17.1

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Re: [FFmpeg-devel] [PATCH 3/3] avutil/softfloat: fix av_sincos_sf()

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 460 bytes --]

On Tue, Jun 20, 2023 at 01:04:24AM +0200, Michael Niedermayer wrote:
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavutil/softfloat.h       | 2 +-
>  libavutil/tests/softfloat.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)

will apply

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In a rich man's house there is no place to spit but his face.
-- Diogenes of Sinope

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Re: [FFmpeg-devel] [PATCH 1/3] avcodec/huffyuvdec: avoid undefined behavior with get_vlc2() failure

[Paul B Mahol]

 Shouldnt it error out instead?
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Re: [FFmpeg-devel] [PATCH 1/3] avcodec/huffyuvdec: avoid undefined behavior with get_vlc2() failure

[Michael Niedermayer]

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On Tue, Jun 20, 2023 at 01:05:45AM +0200, Paul B Mahol wrote:
>  Shouldnt it error out instead?

yes but that would make it slower. Also i think real files (not fuzzeed files)
would use vlc tables that have no "holes" that can generate invalid returns
so the check might on top of being slow also be not that useful.
But i surely can add a check if thats what people prefer?

thx

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Re: [FFmpeg-devel] [PATCH 1/3] avcodec/huffyuvdec: avoid undefined behavior with get_vlc2() failure

[Michael Niedermayer]

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On Tue, Jun 20, 2023 at 01:36:40AM +0200, Michael Niedermayer wrote:
> On Tue, Jun 20, 2023 at 01:05:45AM +0200, Paul B Mahol wrote:
> >  Shouldnt it error out instead?
> 
> yes but that would make it slower. Also i think real files (not fuzzeed files)
> would use vlc tables that have no "holes" that can generate invalid returns
> so the check might on top of being slow also be not that useful.
> But i surely can add a check if thats what people prefer?

no reply so ill apply the original patch, so this is fixed


[...]

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Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data

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