On Thu, Oct 08, 2020 at 09:48:41PM +0200, Andreas Rheinhardt wrote: > Michael Niedermayer: > > Fixes: shift exponent -1 is negative > > Fixes: > > 26107/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PGX_fuzzer-5378790047612928 > > > > Found-by: continuous fuzzing process > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > --- > > libavcodec/pgxdec.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/libavcodec/pgxdec.c b/libavcodec/pgxdec.c > > index 150f8bbf66..5c735894ab 100644 > > --- a/libavcodec/pgxdec.c > > +++ b/libavcodec/pgxdec.c > > @@ -133,14 +133,14 @@ static int pgx_decode_frame(AVCodecContext *avctx, > > void *data, > > if ((ret = ff_set_dimensions(avctx, width, height)) < 0) > > return ret; > > > > - if (depth <= 8) { > > + if (depth > 0 && depth <= 8) { > > avctx->pix_fmt = AV_PIX_FMT_GRAY8; > > bpp = 8; > > - } else if (depth <= 16) { > > + } else if (depth > 0 && depth <= 16) { > > avctx->pix_fmt = AV_PIX_FMT_GRAY16; > > bpp = 16; > > } else { > > - av_log(avctx, AV_LOG_ERROR, "Maximum depth of 16 bits > > supported.\n"); > > + av_log(avctx, AV_LOG_ERROR, "depth %d is invalid or > > unsupported.\n", depth); > > return AVERROR_PATCHWELCOME; > > } > > if (bytestream2_get_bytes_left(&g) < width * height * (bpp >> 3)) > > > I presume the parsed depth to be zero in your testcase. Said number > comes from pgx_get_number() which is only used to parse values for which > a value of zero makes no sense. Wouldn't it make more sense to error out > there if the number is zero?
I was considering that too when i wrote the patch the reason why i picked this is thats where depth is checked already. Checking for depth == 0 in one function and depth > 16 in another feels like its not the clearest way to implement that ... thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB There will always be a question for which you do not know the correct answer.
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