[FFmpeg-devel] [PATCH 2/2] avcodec/h2645_parse: Check HEVC NAL size
Andreas Rheinhardt
andreas.rheinhardt at outlook.com
Sat Apr 30 23:45:04 EEST 2022
Michael Niedermayer:
> Fixes: Assertion failure
> Fixes: 46662/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-4947860854013952
>
> This also results in more frames to be decoded from fate samples
>
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
> libavcodec/h2645_parse.c | 2 +-
> .../ref/fate/hevc-conformance-NoOutPrior_A_Qualcomm_1 | 10 ++++++++++
> tests/ref/fate/hevc-conformance-RAP_B_Bossen_1 | 3 +++
> 3 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/h2645_parse.c b/libavcodec/h2645_parse.c
> index 03780680c6..78ab22b76e 100644
> --- a/libavcodec/h2645_parse.c
> +++ b/libavcodec/h2645_parse.c
> @@ -292,7 +292,7 @@ static int hevc_parse_nal_header(H2645NAL *nal, void *logctx)
> {
> GetBitContext *gb = &nal->gb;
>
> - if (get_bits1(gb) != 0)
> + if (get_bits_left(gb) < 16 || get_bits1(gb) != 0)
> return AVERROR_INVALIDDATA;
>
> nal->type = get_bits(gb, 6);
> diff --git a/tests/ref/fate/hevc-conformance-NoOutPrior_A_Qualcomm_1 b/tests/ref/fate/hevc-conformance-NoOutPrior_A_Qualcomm_1
> index 0c930f6556..3283925e38 100644
> --- a/tests/ref/fate/hevc-conformance-NoOutPrior_A_Qualcomm_1
> +++ b/tests/ref/fate/hevc-conformance-NoOutPrior_A_Qualcomm_1
> @@ -25,6 +25,16 @@
> 0, 19, 19, 1, 599040, 0x4227009b
> 0, 20, 20, 1, 599040, 0x1bda8be4
> 0, 21, 21, 1, 599040, 0xd1d5dcb4
> +0, 22, 22, 1, 599040, 0x58b2edb3
> +0, 23, 23, 1, 599040, 0xd1f795d8
> +0, 24, 24, 1, 599040, 0x3331d5e6
> +0, 25, 25, 1, 599040, 0x5e5ec2c9
> +0, 26, 26, 1, 599040, 0x3b907bf5
> +0, 27, 27, 1, 599040, 0xefcbf471
> +0, 28, 28, 1, 599040, 0x2769a578
> +0, 29, 29, 1, 599040, 0x812ce986
> +0, 30, 30, 1, 599040, 0xf07c212c
> +0, 31, 31, 1, 599040, 0xb5476890
> 0, 32, 32, 1, 599040, 0x00a0249f
> 0, 33, 33, 1, 599040, 0x7263f7cf
> 0, 34, 34, 1, 599040, 0x47054be4
> diff --git a/tests/ref/fate/hevc-conformance-RAP_B_Bossen_1 b/tests/ref/fate/hevc-conformance-RAP_B_Bossen_1
> index e661ff245e..776267b59c 100644
> --- a/tests/ref/fate/hevc-conformance-RAP_B_Bossen_1
> +++ b/tests/ref/fate/hevc-conformance-RAP_B_Bossen_1
> @@ -70,6 +70,9 @@
> 0, 64, 64, 1, 149760, 0x3362678b
> 0, 65, 65, 1, 149760, 0x6e7fc851
> 0, 66, 66, 1, 149760, 0x33f96449
> +0, 67, 67, 1, 149760, 0xd9d05007
> +0, 75, 75, 1, 149760, 0x477f2cf2
> +0, 76, 76, 1, 149760, 0xe1f9ccd0
> 0, 77, 77, 1, 149760, 0xb3ba8cfb
> 0, 78, 78, 1, 149760, 0x64787995
> 0, 79, 79, 1, 149760, 0xc10de4c4
get_bit_length currently presumes every NALU to contain
rbsp_trailing_bits. Yet this is not true for the End of
Sequence/Bitstream units which are just headers without RBSP. For these
units, get_bit_length might truncate them -- it does so for end of
sequence units in H.264. It would not be a serious issue for H.265, as
the semantics of nuh_temporal_id_plus1 require nuh_temporal_id_plus1 to
be 1 for End of Sequence/Bitstream units. Nevertheless I think this
should be coupled with a patch that does not truncate the NAL unit if it
is just a header.
- Andreas
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