Re: [FFmpeg-devel] [PATCH v3 2/5] avcodec/golomb: Prevent shift by negative number
On Mon, Jul 27, 2020 at 11:08:07AM +0200, Andreas Rheinhardt wrote: > This happened in get_ue_golomb() if the cached bitstream reader was in > use, because there was no check to handle the case of the read value > not being in the supported range. > For consistency with the uncached bitstream reader and for compliance > with the documentation, every value not in the 0-8190 range is treated as > error although the cached bitstream reader could actually read values in > the range 0..65534 without problems. > > Signed-off-by: Andreas Rheinhardt > --- > v3: Besides accepting the same range as the uncached version this > version also consumes bits in case of error like the uncached version. > Unfortunately it is not possible to always consume the same number of > bits, because the uncached version will consume 63 bits as soon as all > valid bits are zero, whereas the cached version will only consume 63 > bits if the next 31 bits are zero. > > libavcodec/golomb.h | 5 - > 1 file changed, 4 insertions(+), 1 deletion(-) probably ok thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Modern terrorism, a quick summary: Need oil, start war with country that has oil, kill hundread thousand in war. Let country fall into chaos, be surprised about raise of fundamantalists. Drop more bombs, kill more people, be surprised about them taking revenge and drop even more bombs and strip your own citizens of their rights and freedoms. to be continued 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".
[FFmpeg-devel] [PATCH v3 2/5] avcodec/golomb: Prevent shift by negative number
This happened in get_ue_golomb() if the cached bitstream reader was in
use, because there was no check to handle the case of the read value
not being in the supported range.
For consistency with the uncached bitstream reader and for compliance
with the documentation, every value not in the 0-8190 range is treated as
error although the cached bitstream reader could actually read values in
the range 0..65534 without problems.
Signed-off-by: Andreas Rheinhardt
---
v3: Besides accepting the same range as the uncached version this
version also consumes bits in case of error like the uncached version.
Unfortunately it is not possible to always consume the same number of
bits, because the uncached version will consume 63 bits as soon as all
valid bits are zero, whereas the cached version will only consume 63
bits if the next 31 bits are zero.
libavcodec/golomb.h | 5 -
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/libavcodec/golomb.h b/libavcodec/golomb.h
index 1f988d74aa..aed9b22471 100644
--- a/libavcodec/golomb.h
+++ b/libavcodec/golomb.h
@@ -66,9 +66,12 @@ static inline int get_ue_golomb(GetBitContext *gb)
return ff_ue_golomb_vlc_code[buf];
} else {
int log = 2 * av_log2(buf) - 31;
+
+skip_bits_long(gb, 32 - log);
+if (log < 7)
+return AVERROR_INVALIDDATA;
buf >>= log;
buf--;
-skip_bits_long(gb, 32 - log);
return buf;
}
--
2.20.1
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