On Wed, Jun 19, 2019 at 12:54:25PM -0300, James Almer wrote: > On 6/19/2019 6:22 AM, Michael Niedermayer wrote: > > On Mon, Jun 17, 2019 at 07:55:45PM -0300, James Almer wrote: > >> On 6/17/2019 6:54 PM, Michael Niedermayer wrote: > >>> On Sun, Jun 16, 2019 at 11:10:43PM -0300, James Almer wrote: > >>>> On 6/13/2019 3:32 PM, Michael Niedermayer wrote: > >>>>> Fixes: signed integer overflow: -2147483648 - 1 cannot be represented > >>>>> in type 'int' > >>>>> Fixes: > >>>>> 14880/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_HEVC_fuzzer-5130977304641536 > >>>>> > >>>>> Found-by: continuous fuzzing process > >>>>> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > >>>>> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > >>>>> --- > >>>>> libavcodec/hevc_ps.c | 2 +- > >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>>> > >>>>> diff --git a/libavcodec/hevc_ps.c b/libavcodec/hevc_ps.c > >>>>> index 80df417e4f..0ed6682bb4 100644 > >>>>> --- a/libavcodec/hevc_ps.c > >>>>> +++ b/libavcodec/hevc_ps.c > >>>>> @@ -1596,7 +1596,7 @@ int ff_hevc_decode_nal_pps(GetBitContext *gb, > >>>>> AVCodecContext *avctx, > >>>>> if (pps->num_tile_rows <= 0 || > >>>>> pps->num_tile_rows >= sps->height) { > >>>>> av_log(avctx, AV_LOG_ERROR, "num_tile_rows_minus1 out of > >>>>> range: %d\n", > >>>>> - pps->num_tile_rows - 1); > >>>>> + pps->num_tile_rows - 1U); > >>>> > >>>> The proper fix for this is making pps->num_tile_rows/cols unsigned. > > [...] > >>> > >>> is this here ok if num_tile_rows is 0 ? > >>> for (i = 0; i < pps->num_tile_rows - 1; i++) { (example line from ffmpeg > >>> git) > >>> > >>> i would guess nearly everyone wold say yes without having seen the > >>> discussion about the type. but of course if this is unsigned its not > >>> going to be safe with it being 0. > >> > >> pps->num_tile_rows is set to a value returned by "get_ue_golomb_long() + > >> 1", which will always be in the 1..UINT32_MAX range. It can't be 0, as > >> it would be a bug. Int is definitely not the right type for it. > > > > i dont think num_tile_rows of more than 2^31 (that is the negative when > > signed range) > > makes much sense but sure i can change it to unsigned if preferred. > > Of course it doesn't. In pretty much any sample it will be at least 1 > and at most 22, which is the max value allowed by hevc level 6.2 in > table A.6. Only if the stream reports an undefined level it could go up > to, if i'm reading this right, sps->ctb_height and not sps->height as > the decoder is currently checking. This means you can even replace > get_ue_golomb_long() for a get_ue_golomb(). That would also fix this. > > In any case, the bitstream value is unsigned, so the struct field should > be unsigned as well. Having it be signed and assigning it a value using > a function that potentially returns huge unsigned values introduced this > issue to being with, so instead of working around it using type > promotion, just make it follow the spec.
what would be your feeling/oppinon about making the field uint16_t ? this would make it unsigned in the struct but avoid the problems with unsigned int ? Thanks [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB it is not once nor twice but times without number that the same ideas make their appearance in the world. -- Aristotle
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