[FFmpeg-devel] [PATCH 3/3] avformat/mov: Check for EOF in mov_read_meta()

[Michael Niedermayer]

On Sat, Aug 31, 2019 at 10:36:32AM -0300, James Almer wrote:
> On 8/31/2019 5:47 AM, Michael Niedermayer wrote:
> > On Fri, Aug 30, 2019 at 08:57:29PM -0300, James Almer wrote:
> >> On 8/30/2019 8:25 PM, Michael Niedermayer wrote:
> >>> Fixes: Timeout (195sec -> 2ms)
> >>> Fixes: 16735/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5090676403863552
> >>>
> >>> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> >>> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> >>> ---
> >>>  libavformat/mov.c | 5 ++++-
> >>>  1 file changed, 4 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/libavformat/mov.c b/libavformat/mov.c
> >>> index 675b915906..46c544b61f 100644
> >>> --- a/libavformat/mov.c
> >>> +++ b/libavformat/mov.c
> >>> @@ -4419,7 +4419,10 @@ static int mov_read_custom(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> >>>  static int mov_read_meta(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> >>>  {
> >>>      while (atom.size > 8) {
> >>> -        uint32_t tag = avio_rl32(pb);
> >>> +        uint32_t tag;
> >>> +        if (avio_feof(pb))
> >>> +            return AVERROR_EOF;
> >>> +        tag = avio_rl32(pb);
> >>>          atom.size -= 4;
> >>>          if (tag == MKTAG('h','d','l','r')) {
> >>>              avio_seek(pb, -8, SEEK_CUR);
> >>
> >> Maybe do something like "while (atom.size > 8 && !avio_feof(pb))"
> >> instead, which is similar to the loop in mov_read_default.
> > 
> > Can do but why ?
> > the code in the patch returns an error if the atom is truncated
> > the change suggested does not return an error if the atom is truncated
> > on its own this doesnt sound better
> > 
> > Thanks
> 
> There's Marton's "avformat/utils: return pending IO error on EOF in
> av_read_frame()" patch to check in generic code if avio_feof() != 0 is
> an actual EOF or an IO error, so if you make this code here simply break
> the loop, same as it's done in mov_read_default(), then said generic
> code would be triggered and return the proper error code once the
> current packet is done processing.

are you against the original patch in this thread ?
from reading this its not clear to me if you dislike the original
patch or not ?

thanks

[...]
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