| Message ID | 20200220185056.10900-2-michael@niedermayer.cc |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [FFmpeg-devel,1/2] avcodec/cdtoons: Correct several end of data checks in cdtoons_render_sprite() | expand |
| Context | Check | Description |
|---|---|---|
| andriy/ffmpeg-patchwork | success | Make fate finished |
Are you sure this is correct? Does asan reports exactly overread by 4? On 2/20/20, Michael Niedermayer <michael@niedermayer.cc> wrote: > Fixes: out of array read > Fixes: > 20742/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CDTOONS_fuzzer-5738148607033344 > > Found-by: continuous fuzzing process > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> > --- > libavcodec/cdtoons.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/libavcodec/cdtoons.c b/libavcodec/cdtoons.c > index dc4fa6bf0b..d5dce6351f 100644 > --- a/libavcodec/cdtoons.c > +++ b/libavcodec/cdtoons.c > @@ -269,7 +269,7 @@ static int cdtoons_decode_frame(AVCodecContext *avctx, > void *data, > diff_size = bytestream_get_be32(&buf); > width = bytestream_get_be16(&buf); > height = bytestream_get_be16(&buf); > - if (diff_size < 4 || diff_size - 4 > eod - buf) { > + if (diff_size < 8 || diff_size - 4 > eod - buf) { > av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of > data for Diff frame data.\n"); > return AVERROR_INVALIDDATA; > } > -- > 2.17.1 > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
On Thu, Feb 20, 2020 at 08:11:34PM +0100, Paul B Mahol wrote: > Are you sure this is correct? > Does asan reports exactly overread by 4? the next line passes diff_size - 8 as a unsigned data size if diff_size is smaller than 8, diff_size - 8 is very big and the overread checks which use that will misbehave [...] > > @@ -269,7 +269,7 @@ static int cdtoons_decode_frame(AVCodecContext *avctx, > > void *data, > > diff_size = bytestream_get_be32(&buf); > > width = bytestream_get_be16(&buf); > > height = bytestream_get_be16(&buf); > > - if (diff_size < 4 || diff_size - 4 > eod - buf) { > > + if (diff_size < 8 || diff_size - 4 > eod - buf) { > > av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of > > data for Diff frame data.\n"); > > return AVERROR_INVALIDDATA; > > } [...]
On 2/20/20, Michael Niedermayer <michaelni@gmx.at> wrote: > On Thu, Feb 20, 2020 at 08:11:34PM +0100, Paul B Mahol wrote: >> Are you sure this is correct? >> Does asan reports exactly overread by 4? > > the next line passes diff_size - 8 as a unsigned data size > if diff_size is smaller than 8, diff_size - 8 is very big and > the overread checks which use that will misbehave > OK then. > > [...] >> > @@ -269,7 +269,7 @@ static int cdtoons_decode_frame(AVCodecContext >> > *avctx, >> > void *data, >> > diff_size = bytestream_get_be32(&buf); >> > width = bytestream_get_be16(&buf); >> > height = bytestream_get_be16(&buf); >> > - if (diff_size < 4 || diff_size - 4 > eod - buf) { >> > + if (diff_size < 8 || diff_size - 4 > eod - buf) { >> > av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out >> > of >> > data for Diff frame data.\n"); >> > return AVERROR_INVALIDDATA; >> > } > > [...] > -- > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB > > The misfortune of the wise is better than the prosperity of the fool. > -- Epicurus >
On Thu, Feb 20, 2020 at 11:29:51PM +0100, Paul B Mahol wrote: > On 2/20/20, Michael Niedermayer <michaelni@gmx.at> wrote: > > On Thu, Feb 20, 2020 at 08:11:34PM +0100, Paul B Mahol wrote: > >> Are you sure this is correct? > >> Does asan reports exactly overread by 4? > > > > the next line passes diff_size - 8 as a unsigned data size > > if diff_size is smaller than 8, diff_size - 8 is very big and > > the overread checks which use that will misbehave > > > > OK then. will apply thx [...]
diff --git a/libavcodec/cdtoons.c b/libavcodec/cdtoons.c index dc4fa6bf0b..d5dce6351f 100644 --- a/libavcodec/cdtoons.c +++ b/libavcodec/cdtoons.c @@ -269,7 +269,7 @@ static int cdtoons_decode_frame(AVCodecContext *avctx, void *data, diff_size = bytestream_get_be32(&buf); width = bytestream_get_be16(&buf); height = bytestream_get_be16(&buf); - if (diff_size < 4 || diff_size - 4 > eod - buf) { + if (diff_size < 8 || diff_size - 4 > eod - buf) { av_log(avctx, AV_LOG_WARNING, "Ran (seriously) out of data for Diff frame data.\n"); return AVERROR_INVALIDDATA; }
Fixes: out of array read Fixes: 20742/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_CDTOONS_fuzzer-5738148607033344 Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> --- libavcodec/cdtoons.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)