Re: [FFmpeg-devel] [PATCH 2/2] avcodec/vc1_block: Fix invalid shifts in vc1_decode_i_blocks()
On Sat, Jun 22, 2019 at 02:21:43PM +0200, Michael Niedermayer wrote: > Fixes: left shift of negative value -9 > Fixes: > 15299/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSS2_fuzzer-5660922678345728 > > Found-by: continuous fuzzing process > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > Signed-off-by: Michael Niedermayer > --- > libavcodec/vc1_block.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) Will apply these 2 in a few days unless there are further objections, benchmarks, disassemblies showing a slowdown My tests indicate as already stated that the asm code generated is identical [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB There will always be a question for which you do not know the correct answer. signature.asc Description: PGP signature ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-devel] [PATCH 2/2] avcodec/vc1_block: Fix invalid shifts in vc1_decode_i_blocks()
On Thu, Jun 27, 2019 at 12:40:58AM +0200, Michael Niedermayer wrote:
> On Sat, Jun 22, 2019 at 04:55:47PM +0200, Paul B Mahol wrote:
> > On 6/22/19, Michael Niedermayer wrote:
> > > Fixes: left shift of negative value -9
> > > Fixes:
> > > 15299/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSS2_fuzzer-5660922678345728
> > >
> > > Found-by: continuous fuzzing process
> > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > > Signed-off-by: Michael Niedermayer
> > > ---
> > > libavcodec/vc1_block.c | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c
> > > index 7e41791832..6137252580 100644
> > > --- a/libavcodec/vc1_block.c
> > > +++ b/libavcodec/vc1_block.c
> > > @@ -2600,13 +2600,13 @@ static void vc1_decode_i_blocks(VC1Context *v)
> > > if (v->rangeredfrm)
> > > for (k = 0; k < 6; k++)
> > > for (j = 0; j < 64; j++)
> > > -v->block[v->cur_blk_idx][block_map[k]][j] <<=
> > > 1;
> > > +v->block[v->cur_blk_idx][block_map[k]][j] *=
> > > 2;
> > > vc1_put_blocks_clamped(v, 1);
> > > } else {
> > > if (v->rangeredfrm)
> > > for (k = 0; k < 6; k++)
> > > for (j = 0; j < 64; j++)
> > > -v->block[v->cur_blk_idx][block_map[k]][j] =
> > > (v->block[v->cur_blk_idx][block_map[k]][j] - 64) << 1;
> > > +v->block[v->cur_blk_idx][block_map[k]][j] =
> > > (v->block[v->cur_blk_idx][block_map[k]][j] - 64) * 2;
> > > vc1_put_blocks_clamped(v, 0);
> > > }
> > >
> > > --
> > > 2.22.0
> > >
> > > ___
> > > ffmpeg-devel mailing list
> > > ffmpeg-devel@ffmpeg.org
> > > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > >
> > > To unsubscribe, visit link above, or email
> > > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
> >
> >
> > This is much slower.
>
> please provide your testcase and benchmarks or disassmbly
Noone ?
people just claim "This is much slower." without having tested it ?
ok heres the disassmbly of the 2 inner loops from the code with the patch
applied
(that is with the multiplications in the source tested with gcc (4.8.5)
as you can see all multiplications are optimized to shifts or additions
even the old gcc used optmizes it to a shift
.p2align 4,,10
.p2align 3
.L1034:
salw(%rax)
addq$2, %rax
cmpq%rdx, %rax
jne .L1034
...
.p2align 4,,10
.p2align 3
.L1039:
movswl (%rax), %edx
addq$2, %rax
leal-128(%rdx,%rdx), %edx
movw%dx, -2(%rax)
cmpq%rcx, %rax
jne .L1039
before the patch it looked like this:
.p2align 4,,10
.p2align 3
.L1034:
salw(%rax)
addq$2, %rax
cmpq%rdx, %rax
jne .L1034
...
.p2align 4,,10
.p2align 3
.L1039:
movswl (%rax), %edx
addq$2, %rax
leal-128(%rdx,%rdx), %edx
movw%dx, -2(%rax)
cmpq%rcx, %rax
jne .L1039
I used this patch for testing and finding the parts of the code:
--- a/libavcodec/vc1_block.c
+++ b/libavcodec/vc1_block.c
@@ -2579,16 +2579,20 @@ static void vc1_decode_i_blocks(VC1Context *v)
if (v->overlap && v->pq >= 9) {
ff_vc1_i_overlap_filter(v);
+__asm volatile ("MARKA\n\t");
if (v->rangeredfrm)
for (k = 0; k < 6; k++)
for (j = 0; j < 64; j++)
-v->block[v->cur_blk_idx][block_map[k]][j] *= 2;
+v->block[v->cur_blk_idx][block_map[k]][j] <<= 1;
+__asm volatile ("MARKB\n\t");
vc1_put_blocks_clamped(v, 1);
} else {
+__asm volatile ("MARKC\n\t");
if (v->rangeredfrm)
for (k = 0; k < 6; k++)
for (j = 0; j < 64; j++)
-v->block[v->cur_blk_idx][block_map[k]][j] =
(v->block[v->cur_blk_idx][block_map[k]][j] - 64) * 2;
+v->block[v->cur_blk_idx][block_map[k]][j] =
(v->block[v->cur_blk_idx][block_map[k]][j] - 64) << 1;
+__asm volatile ("MARKD\n\t");
vc1_put_blocks_clamped(v, 0);
}
[...]
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If you think the mosad wants you dead since a long time then you are either
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Re: [FFmpeg-devel] [PATCH 2/2] avcodec/vc1_block: Fix invalid shifts in vc1_decode_i_blocks()
On Sat, Jun 22, 2019 at 04:55:47PM +0200, Paul B Mahol wrote:
> On 6/22/19, Michael Niedermayer wrote:
> > Fixes: left shift of negative value -9
> > Fixes:
> > 15299/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSS2_fuzzer-5660922678345728
> >
> > Found-by: continuous fuzzing process
> > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer
> > ---
> > libavcodec/vc1_block.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c
> > index 7e41791832..6137252580 100644
> > --- a/libavcodec/vc1_block.c
> > +++ b/libavcodec/vc1_block.c
> > @@ -2600,13 +2600,13 @@ static void vc1_decode_i_blocks(VC1Context *v)
> > if (v->rangeredfrm)
> > for (k = 0; k < 6; k++)
> > for (j = 0; j < 64; j++)
> > -v->block[v->cur_blk_idx][block_map[k]][j] <<=
> > 1;
> > +v->block[v->cur_blk_idx][block_map[k]][j] *= 2;
> > vc1_put_blocks_clamped(v, 1);
> > } else {
> > if (v->rangeredfrm)
> > for (k = 0; k < 6; k++)
> > for (j = 0; j < 64; j++)
> > -v->block[v->cur_blk_idx][block_map[k]][j] =
> > (v->block[v->cur_blk_idx][block_map[k]][j] - 64) << 1;
> > +v->block[v->cur_blk_idx][block_map[k]][j] =
> > (v->block[v->cur_blk_idx][block_map[k]][j] - 64) * 2;
> > vc1_put_blocks_clamped(v, 0);
> > }
> >
> > --
> > 2.22.0
> >
> > ___
> > ffmpeg-devel mailing list
> > ffmpeg-devel@ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
>
>
> This is much slower.
please provide your testcase and benchmarks or disassmbly
thanks
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
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people will find a way around the laws. -- Plato
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Re: [FFmpeg-devel] [PATCH 2/2] avcodec/vc1_block: Fix invalid shifts in vc1_decode_i_blocks()
On 6/22/19, Michael Niedermayer wrote:
> Fixes: left shift of negative value -9
> Fixes:
> 15299/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSS2_fuzzer-5660922678345728
>
> Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer
> ---
> libavcodec/vc1_block.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c
> index 7e41791832..6137252580 100644
> --- a/libavcodec/vc1_block.c
> +++ b/libavcodec/vc1_block.c
> @@ -2600,13 +2600,13 @@ static void vc1_decode_i_blocks(VC1Context *v)
> if (v->rangeredfrm)
> for (k = 0; k < 6; k++)
> for (j = 0; j < 64; j++)
> -v->block[v->cur_blk_idx][block_map[k]][j] <<=
> 1;
> +v->block[v->cur_blk_idx][block_map[k]][j] *= 2;
> vc1_put_blocks_clamped(v, 1);
> } else {
> if (v->rangeredfrm)
> for (k = 0; k < 6; k++)
> for (j = 0; j < 64; j++)
> -v->block[v->cur_blk_idx][block_map[k]][j] =
> (v->block[v->cur_blk_idx][block_map[k]][j] - 64) << 1;
> +v->block[v->cur_blk_idx][block_map[k]][j] =
> (v->block[v->cur_blk_idx][block_map[k]][j] - 64) * 2;
> vc1_put_blocks_clamped(v, 0);
> }
>
> --
> 2.22.0
>
> ___
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> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
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> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
This is much slower.
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[FFmpeg-devel] [PATCH 2/2] avcodec/vc1_block: Fix invalid shifts in vc1_decode_i_blocks()
Fixes: left shift of negative value -9
Fixes:
15299/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSS2_fuzzer-5660922678345728
Found-by: continuous fuzzing process
https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer
---
libavcodec/vc1_block.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c
index 7e41791832..6137252580 100644
--- a/libavcodec/vc1_block.c
+++ b/libavcodec/vc1_block.c
@@ -2600,13 +2600,13 @@ static void vc1_decode_i_blocks(VC1Context *v)
if (v->rangeredfrm)
for (k = 0; k < 6; k++)
for (j = 0; j < 64; j++)
-v->block[v->cur_blk_idx][block_map[k]][j] <<= 1;
+v->block[v->cur_blk_idx][block_map[k]][j] *= 2;
vc1_put_blocks_clamped(v, 1);
} else {
if (v->rangeredfrm)
for (k = 0; k < 6; k++)
for (j = 0; j < 64; j++)
-v->block[v->cur_blk_idx][block_map[k]][j] =
(v->block[v->cur_blk_idx][block_map[k]][j] - 64) << 1;
+v->block[v->cur_blk_idx][block_map[k]][j] =
(v->block[v->cur_blk_idx][block_map[k]][j] - 64) * 2;
vc1_put_blocks_clamped(v, 0);
}
--
2.22.0
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