On Fri, Jan 22, 2021 at 07:16:58PM -0300, James Almer wrote: > On 1/22/2021 7:10 PM, Michael Niedermayer wrote: > > On Fri, Jan 22, 2021 at 11:23:09AM -0300, James Almer wrote: > > > On 1/22/2021 11:09 AM, Michael Niedermayer wrote: > > > > Fixes: signed integer overflow: 9223372036854775723 + 8192 cannot be > > > > represented in type 'long' > > > > Fixes: > > > > 29072/clusterfuzz-testcase-minimized-ffmpeg_dem_MXF_fuzzer-4812604904177664 > > > > > > > > Found-by: continuous fuzzing process > > > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > > > --- > > > > libavformat/mxfdec.c | 4 +++- > > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c > > > > index 4c932e954c..f1167761f9 100644 > > > > --- a/libavformat/mxfdec.c > > > > +++ b/libavformat/mxfdec.c > > > > @@ -2865,8 +2865,10 @@ static int mxf_read_local_tags(MXFContext *mxf, > > > > KLVPacket *klv, MXFMetadataReadF > > > > int ret; > > > > int tag = avio_rb16(pb); > > > > int size = avio_rb16(pb); /* KLV specified by 0x53 */ > > > > - uint64_t next = avio_tell(pb) + size; > > > > + uint64_t next = avio_tell(pb); > > > > UID uid = {0}; > > > > + if (next > INT64_MAX - size) > > > > + size = 0; > > > > > > You're discarding the tag's size. The code below could misbehave as it > > > will > > > assume it's an empty tag when it's not. Not to mention the log message > > > will > > > print a bogus value. > > > > > > Abort instead (Invalid data or erange) in this scenario since going beyond > > > INT64_MAX is clearly not supported by avio, and then do next += size to > > > ensure the avio_seek() at the end works as expected. > > > > I dont think this strictly implies being beyond INT64_MAX. > > but i wanted to redo this patch anyway as it contained another bug > > so next suggestion: > > > > @@ -2865,8 +2865,11 @@ static int mxf_read_local_tags(MXFContext *mxf, > > KLVPacket *klv, MXFMetadataReadF > > int ret; > > int tag = avio_rb16(pb); > > int size = avio_rb16(pb); /* KLV specified by 0x53 */ > > - uint64_t next = avio_tell(pb) + size; > > + int64_t next = avio_tell(pb); > > UID uid = {0}; > > + if (next < 0 || next > INT64_MAX - size) > > + return next < 0 ? next : AVERROR_INVALIDDATA; > > + next += size; > > av_log(mxf->fc, AV_LOG_TRACE, "local tag %#04x size %d\n", tag, > > size); > > if (!size) { /* ignore empty tag, needed for some files with > > empty UMID tag */ > > > > > > thx > > That's better, yes.
will apply thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB When you are offended at any man's fault, turn to yourself and study your own failings. Then you will forget your anger. -- Epictetus
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