| Message ID | 20170510003722.30567-1-michael@niedermayer.cc |
|---|---|
| State | New |
| Headers | show |
Hi, On Tue, May 9, 2017 at 8:37 PM, Michael Niedermayer <michael@niedermayer.cc> wrote: > Fixes: out of array access > Fixes: 1434/clusterfuzz-testcase-minimized-6314998085189632 > Fixes: 1435/clusterfuzz-testcase-minimized-6483783723253760 > > Found-by: continuous fuzzing process https://github.com/google/oss- > fuzz/tree/master/targets/ffmpeg > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> > --- > libavcodec/webp.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/libavcodec/webp.c b/libavcodec/webp.c > index 16c3ae2662..23ed4bc26f 100644 > --- a/libavcodec/webp.c > +++ b/libavcodec/webp.c > @@ -1330,12 +1330,17 @@ static int vp8_lossy_decode_frame(AVCodecContext > *avctx, AVFrame *p, > WebPContext *s = avctx->priv_data; > AVPacket pkt; > int ret; > + enum AVPixelFormat wanted_pix_fmt = s->has_alpha ? > AV_PIX_FMT_YUVA420P : AV_PIX_FMT_YUV420P; > + > + if (s->initialized && wanted_pix_fmt != avctx->pix_fmt) { > + ff_vp8_decode_free(avctx); > + s->initialized = 0; > + } > > if (!s->initialized) { > ff_vp8_decode_init(avctx); > s->initialized = 1; > - if (s->has_alpha) > - avctx->pix_fmt = AV_PIX_FMT_YUVA420P; > + avctx->pix_fmt = wanted_pix_fmt; > } > s->lossless = 0; What is the out of array access? webp is intra only and the only thing that is initialized with memory in that call is reference frames. What's going on here? Ronald
On Tue, May 09, 2017 at 09:08:08PM -0400, Ronald S. Bultje wrote: > Hi, > > On Tue, May 9, 2017 at 8:37 PM, Michael Niedermayer <michael@niedermayer.cc> > wrote: > > > Fixes: out of array access > > Fixes: 1434/clusterfuzz-testcase-minimized-6314998085189632 > > Fixes: 1435/clusterfuzz-testcase-minimized-6483783723253760 > > > > Found-by: continuous fuzzing process https://github.com/google/oss- > > fuzz/tree/master/targets/ffmpeg > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> > > --- > > libavcodec/webp.c | 9 +++++++-- > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > diff --git a/libavcodec/webp.c b/libavcodec/webp.c > > index 16c3ae2662..23ed4bc26f 100644 > > --- a/libavcodec/webp.c > > +++ b/libavcodec/webp.c > > @@ -1330,12 +1330,17 @@ static int vp8_lossy_decode_frame(AVCodecContext > > *avctx, AVFrame *p, > > WebPContext *s = avctx->priv_data; > > AVPacket pkt; > > int ret; > > + enum AVPixelFormat wanted_pix_fmt = s->has_alpha ? > > AV_PIX_FMT_YUVA420P : AV_PIX_FMT_YUV420P; > > + > > + if (s->initialized && wanted_pix_fmt != avctx->pix_fmt) { > > + ff_vp8_decode_free(avctx); > > + s->initialized = 0; > > + } > > > > if (!s->initialized) { > > ff_vp8_decode_init(avctx); > > s->initialized = 1; > > - if (s->has_alpha) > > - avctx->pix_fmt = AV_PIX_FMT_YUVA420P; > > + avctx->pix_fmt = wanted_pix_fmt; > > } > > s->lossless = 0; > > > What is the out of array access? webp is intra only and the only thing that > is initialized with memory in that call is reference frames. What's going > on here? webp uses the same context as VP8, and it changes the pixel format as it needs. Vp8 doesnt work if its format is changed under its feet the reinit seemed reasonable cleanish to handle it. There are a few other ways the same can be achived Do you have a better idea or see something missing ? thx [...]
Hi, On Tue, May 9, 2017 at 9:24 PM, Michael Niedermayer <michael@niedermayer.cc> wrote: > On Tue, May 09, 2017 at 09:08:08PM -0400, Ronald S. Bultje wrote: > > Hi, > > > > On Tue, May 9, 2017 at 8:37 PM, Michael Niedermayer > <michael@niedermayer.cc> > > wrote: > > > > > Fixes: out of array access > > > Fixes: 1434/clusterfuzz-testcase-minimized-6314998085189632 > > > Fixes: 1435/clusterfuzz-testcase-minimized-6483783723253760 > > > > > > Found-by: continuous fuzzing process https://github.com/google/oss- > > > fuzz/tree/master/targets/ffmpeg > > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> > > > --- > > > libavcodec/webp.c | 9 +++++++-- > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > diff --git a/libavcodec/webp.c b/libavcodec/webp.c > > > index 16c3ae2662..23ed4bc26f 100644 > > > --- a/libavcodec/webp.c > > > +++ b/libavcodec/webp.c > > > @@ -1330,12 +1330,17 @@ static int vp8_lossy_decode_frame( > AVCodecContext > > > *avctx, AVFrame *p, > > > WebPContext *s = avctx->priv_data; > > > AVPacket pkt; > > > int ret; > > > + enum AVPixelFormat wanted_pix_fmt = s->has_alpha ? > > > AV_PIX_FMT_YUVA420P : AV_PIX_FMT_YUV420P; > > > + > > > + if (s->initialized && wanted_pix_fmt != avctx->pix_fmt) { > > > + ff_vp8_decode_free(avctx); > > > + s->initialized = 0; > > > + } > > > > > > if (!s->initialized) { > > > ff_vp8_decode_init(avctx); > > > s->initialized = 1; > > > - if (s->has_alpha) > > > - avctx->pix_fmt = AV_PIX_FMT_YUVA420P; > > > + avctx->pix_fmt = wanted_pix_fmt; > > > } > > > s->lossless = 0; > > > > > > What is the out of array access? webp is intra only and the only thing > that > > is initialized with memory in that call is reference frames. What's going > > on here? > > webp uses the same context as VP8, and it changes the pixel format > as it needs. Vp8 doesnt work if its format is changed under its feet > > the reinit seemed reasonable cleanish to handle it. There are a few > other ways the same can be achived What is the out of array access? Ronald
Hi, On Tue, May 9, 2017 at 9:24 PM, Michael Niedermayer <michael@niedermayer.cc> wrote: > On Tue, May 09, 2017 at 09:08:08PM -0400, Ronald S. Bultje wrote: > > Hi, > > > > On Tue, May 9, 2017 at 8:37 PM, Michael Niedermayer > <michael@niedermayer.cc> > > wrote: > > > > > Fixes: out of array access > > > Fixes: 1434/clusterfuzz-testcase-minimized-6314998085189632 > > > Fixes: 1435/clusterfuzz-testcase-minimized-6483783723253760 > > > > > > Found-by: continuous fuzzing process https://github.com/google/oss- > > > fuzz/tree/master/targets/ffmpeg > > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> > > > --- > > > libavcodec/webp.c | 9 +++++++-- > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > diff --git a/libavcodec/webp.c b/libavcodec/webp.c > > > index 16c3ae2662..23ed4bc26f 100644 > > > --- a/libavcodec/webp.c > > > +++ b/libavcodec/webp.c > > > @@ -1330,12 +1330,17 @@ static int vp8_lossy_decode_frame( > AVCodecContext > > > *avctx, AVFrame *p, > > > WebPContext *s = avctx->priv_data; > > > AVPacket pkt; > > > int ret; > > > + enum AVPixelFormat wanted_pix_fmt = s->has_alpha ? > > > AV_PIX_FMT_YUVA420P : AV_PIX_FMT_YUV420P; > > > + > > > + if (s->initialized && wanted_pix_fmt != avctx->pix_fmt) { > > > + ff_vp8_decode_free(avctx); > > > + s->initialized = 0; > > > + } > > > > > > if (!s->initialized) { > > > ff_vp8_decode_init(avctx); > > > s->initialized = 1; > > > - if (s->has_alpha) > > > - avctx->pix_fmt = AV_PIX_FMT_YUVA420P; > > > + avctx->pix_fmt = wanted_pix_fmt; > > > } > > > s->lossless = 0; > > > > > > What is the out of array access? webp is intra only and the only thing > that > > is initialized with memory in that call is reference frames. What's going > > on here? > > webp uses the same context as VP8, and it changes the pixel format > as it needs. Vp8 doesnt work if its format is changed under its feet I think what you're trying to say is that it doesn't work with RGBA as pixel format (it shouldn't need a reset between yuv420p and yuv420pa). We indeed don't set pix_fmt if has_alpha = 0, which seems like the core of the issue. I'm not sure you need to call ff_vp8_decode_init() twice, in fact I'm pretty sure you don't have to. It may also help to assert that pix_fmt is yuv420p(a) when calling vp8 functions. Ronald
On Wed, May 10, 2017 at 08:10:23AM -0400, Ronald S. Bultje wrote: > Hi, > > On Tue, May 9, 2017 at 9:24 PM, Michael Niedermayer <michael@niedermayer.cc> > wrote: > > > On Tue, May 09, 2017 at 09:08:08PM -0400, Ronald S. Bultje wrote: > > > Hi, > > > > > > On Tue, May 9, 2017 at 8:37 PM, Michael Niedermayer > > <michael@niedermayer.cc> > > > wrote: > > > > > > > Fixes: out of array access > > > > Fixes: 1434/clusterfuzz-testcase-minimized-6314998085189632 > > > > Fixes: 1435/clusterfuzz-testcase-minimized-6483783723253760 > > > > > > > > Found-by: continuous fuzzing process https://github.com/google/oss- > > > > fuzz/tree/master/targets/ffmpeg > > > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> > > > > --- > > > > libavcodec/webp.c | 9 +++++++-- > > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/libavcodec/webp.c b/libavcodec/webp.c > > > > index 16c3ae2662..23ed4bc26f 100644 > > > > --- a/libavcodec/webp.c > > > > +++ b/libavcodec/webp.c > > > > @@ -1330,12 +1330,17 @@ static int vp8_lossy_decode_frame( > > AVCodecContext > > > > *avctx, AVFrame *p, > > > > WebPContext *s = avctx->priv_data; > > > > AVPacket pkt; > > > > int ret; > > > > + enum AVPixelFormat wanted_pix_fmt = s->has_alpha ? > > > > AV_PIX_FMT_YUVA420P : AV_PIX_FMT_YUV420P; > > > > + > > > > + if (s->initialized && wanted_pix_fmt != avctx->pix_fmt) { > > > > + ff_vp8_decode_free(avctx); > > > > + s->initialized = 0; > > > > + } > > > > > > > > if (!s->initialized) { > > > > ff_vp8_decode_init(avctx); > > > > s->initialized = 1; > > > > - if (s->has_alpha) > > > > - avctx->pix_fmt = AV_PIX_FMT_YUVA420P; > > > > + avctx->pix_fmt = wanted_pix_fmt; > > > > } > > > > s->lossless = 0; > > > > > > > > > What is the out of array access? webp is intra only and the only thing > > that > > > is initialized with memory in that call is reference frames. What's going > > > on here? > > > > webp uses the same context as VP8, and it changes the pixel format > > as it needs. Vp8 doesnt work if its format is changed under its feet > > > I think what you're trying to say is that it doesn't work with RGBA as > pixel format (it shouldn't need a reset between yuv420p and yuv420pa). We > indeed don't set pix_fmt if has_alpha = 0, which seems like the core of the > issue. I'm not sure you need to call ff_vp8_decode_init() twice, in fact > I'm pretty sure you don't have to. It may also help to assert that pix_fmt > is yuv420p(a) when calling vp8 functions. The reason why i replied privatly is because the details of security issues should not be discussed in public before the fixes are available in releases. As these details are usefull not only to us understanding an issue but also to an attacker understanding and expoiting it Ill reply privatly again to awnser your questions thx [...]
On Wed, 10 May 2017 15:39:45 +0200 Michael Niedermayer <michael@niedermayer.cc> wrote: > On Wed, May 10, 2017 at 08:10:23AM -0400, Ronald S. Bultje wrote: > > Hi, > > > > On Tue, May 9, 2017 at 9:24 PM, Michael Niedermayer <michael@niedermayer.cc> > > wrote: > > > > > On Tue, May 09, 2017 at 09:08:08PM -0400, Ronald S. Bultje wrote: > > > > Hi, > > > > > > > > On Tue, May 9, 2017 at 8:37 PM, Michael Niedermayer > > > <michael@niedermayer.cc> > > > > wrote: > > > > > > > > > Fixes: out of array access > > > > > Fixes: 1434/clusterfuzz-testcase-minimized-6314998085189632 > > > > > Fixes: 1435/clusterfuzz-testcase-minimized-6483783723253760 > > > > > > > > > > Found-by: continuous fuzzing process https://github.com/google/oss- > > > > > fuzz/tree/master/targets/ffmpeg > > > > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> > > > > > --- > > > > > libavcodec/webp.c | 9 +++++++-- > > > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/libavcodec/webp.c b/libavcodec/webp.c > > > > > index 16c3ae2662..23ed4bc26f 100644 > > > > > --- a/libavcodec/webp.c > > > > > +++ b/libavcodec/webp.c > > > > > @@ -1330,12 +1330,17 @@ static int vp8_lossy_decode_frame( > > > AVCodecContext > > > > > *avctx, AVFrame *p, > > > > > WebPContext *s = avctx->priv_data; > > > > > AVPacket pkt; > > > > > int ret; > > > > > + enum AVPixelFormat wanted_pix_fmt = s->has_alpha ? > > > > > AV_PIX_FMT_YUVA420P : AV_PIX_FMT_YUV420P; > > > > > + > > > > > + if (s->initialized && wanted_pix_fmt != avctx->pix_fmt) { > > > > > + ff_vp8_decode_free(avctx); > > > > > + s->initialized = 0; > > > > > + } > > > > > > > > > > if (!s->initialized) { > > > > > ff_vp8_decode_init(avctx); > > > > > s->initialized = 1; > > > > > - if (s->has_alpha) > > > > > - avctx->pix_fmt = AV_PIX_FMT_YUVA420P; > > > > > + avctx->pix_fmt = wanted_pix_fmt; > > > > > } > > > > > s->lossless = 0; > > > > > > > > > > > > What is the out of array access? webp is intra only and the only thing > > > that > > > > is initialized with memory in that call is reference frames. What's going > > > > on here? > > > > > > webp uses the same context as VP8, and it changes the pixel format > > > as it needs. Vp8 doesnt work if its format is changed under its feet > > > > > > I think what you're trying to say is that it doesn't work with RGBA as > > pixel format (it shouldn't need a reset between yuv420p and yuv420pa). We > > indeed don't set pix_fmt if has_alpha = 0, which seems like the core of the > > issue. I'm not sure you need to call ff_vp8_decode_init() twice, in fact > > I'm pretty sure you don't have to. It may also help to assert that pix_fmt > > is yuv420p(a) when calling vp8 functions. > > The reason why i replied privatly is because the details of security > issues should not be discussed in public before the fixes are available > in releases. As these details are usefull not only to us understanding > an issue but also to an attacker understanding and expoiting it > > Ill reply privatly again to awnser your questions Uh, just no.
diff --git a/libavcodec/webp.c b/libavcodec/webp.c index 16c3ae2662..23ed4bc26f 100644 --- a/libavcodec/webp.c +++ b/libavcodec/webp.c @@ -1330,12 +1330,17 @@ static int vp8_lossy_decode_frame(AVCodecContext *avctx, AVFrame *p, WebPContext *s = avctx->priv_data; AVPacket pkt; int ret; + enum AVPixelFormat wanted_pix_fmt = s->has_alpha ? AV_PIX_FMT_YUVA420P : AV_PIX_FMT_YUV420P; + + if (s->initialized && wanted_pix_fmt != avctx->pix_fmt) { + ff_vp8_decode_free(avctx); + s->initialized = 0; + } if (!s->initialized) { ff_vp8_decode_init(avctx); s->initialized = 1; - if (s->has_alpha) - avctx->pix_fmt = AV_PIX_FMT_YUVA420P; + avctx->pix_fmt = wanted_pix_fmt; } s->lossless = 0;
Fixes: out of array access Fixes: 1434/clusterfuzz-testcase-minimized-6314998085189632 Fixes: 1435/clusterfuzz-testcase-minimized-6483783723253760 Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> --- libavcodec/webp.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)