On Tue, Jan 17, 2017 at 6:48 PM, Xiang, Haihao <haihao.xi...@intel.com> wrote:
> On Tue, 2017-01-17 at 13:15 -0800, Sean V Kelley wrote: > > From: Kuang-che Wu <k...@chromium.org> > > > > shift uint32_t by 32 bits is undefined behavior. > > > > For this particular case: when invoke avc_bitstream_put_ui() with 32 > > bits value at byte position of multiple of 4, existing 32 bits garbage > > data in the buffer may be retained instead of cleared. The result is, > > the position of NALU start code (0x00000001) looks like overwritten by > > garbage value. > > > > Patch has been tested and used upstream: > > https://chromium-review.googlesource.com/#/c/410541/ > > > > Signed-off-by: Kuang-che Wu <k...@chromium.org> > > Signed-off-by: Sean V Kelley <sea...@posteo.de> > > --- > > src/i965_encoder_utils.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/src/i965_encoder_utils.c b/src/i965_encoder_utils.c > > index ac58cd1a..e061d071 100644 > > --- a/src/i965_encoder_utils.c > > +++ b/src/i965_encoder_utils.c > > @@ -134,7 +134,11 @@ avc_bitstream_put_ui(avc_bitstream *bs, unsigned > int val, int size_in_bits) > > bs->buffer[pos] = (bs->buffer[pos] << size_in_bits | val); > > } else { > > size_in_bits -= bit_left; > > - bs->buffer[pos] = (bs->buffer[pos] << bit_left) | (val >> > size_in_bits); > > + if (bit_left == 32) { > > + bs->buffer[pos] = (val >> size_in_bits); > > The input value of size_in_bits should be less than or equal to 32, so now > the > value of size_in_bits is 0 for this case, I think "bs->buffer[pos] = val" > is > more clear. > That's a reasonable change. Thanks Haihao. I'll update the patch. Sean > > > + } else { > > + bs->buffer[pos] = (bs->buffer[pos] << bit_left) | (val >> > size_in_bits); > > + } > > bs->buffer[pos] = swap32(bs->buffer[pos]); > > > > if (pos + 1 == bs->max_size_in_dword) { > _______________________________________________ > Libva mailing list > Libva@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/libva > -- Sean V. Kelley <sean.v.kel...@intel.com> Open Source Technology Center / SSG Intel Corp.
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