On Tue, Mar 06, 2018 at 11:27:54PM -0300, James Almer wrote:
> On 3/6/2018 11:03 PM, James Almer wrote:
> > On 3/6/2018 10:47 PM, Michael Niedermayer wrote:
> >> On Tue, Mar 06, 2018 at 01:42:36AM -0300, James Almer wrote:
> >>> This prevents leaks in the rare cases the function is called when
> >>> extradata
> >>> already exists.
> >>>
> >>> Signed-off-by: James Almer <jamr...@gmail.com>
> >>> ---
> >>> libavformat/utils.c | 1 +
> >>> 1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/libavformat/utils.c b/libavformat/utils.c
> >>> index 72531d4185..31340a484b 100644
> >>> --- a/libavformat/utils.c
> >>> +++ b/libavformat/utils.c
> >>> @@ -3245,6 +3245,7 @@ int ff_alloc_extradata(AVCodecParameters *par, int
> >>> size)
> >>> {
> >>> int ret;
> >>>
> >>> + av_freep(&par->extradata);
> >>> if (size < 0 || size >= INT32_MAX - AV_INPUT_BUFFER_PADDING_SIZE) {
> >>> par->extradata = NULL;
> >>> par->extradata_size = 0;
> >>
> >> This causes memory corruption
> >> ...
> >> [mpegts @ 0x7f8c74000a80] PES packet size mismatch
> >> *** Error in `./ffplay': double free or corruption (fasttop):
> >> 0x00007f8c7402d9c0 ***
> >> Aborted (core dumped)
> >
> > Is something freeing extradata and leaving a dangling pointer before
> > eventually calling ff_alloc_extradata()?
> > At least the two calls in mpegts.c don't seem to do that.
> >
> >>
> >> I think this should not have been applied so quickly, i tested it as soon
> >> as i
> >> had time and saw it but it was applied already
> >
> > Fate passed when i tested it, and i got a positive review from the
> > author of the function in question, that's why i pushed it. Sorry.
> >
> >>
> >> If it helps i can debug the cases i see to find out which calls cause them
> >> but
> >> someone will still have to review all call sites probably for this change
> >> to
> >> be safe
> >
> > Yes, help would be welcome. Crashes like this probably hint at frees
> > leaving dangling pointers across the codebase.
>
> Does the attached patch fix this crash?yes, thanks! [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In a rich man's house there is no place to spit but his face. -- Diogenes of Sinope
signature.asc
Description: PGP signature
_______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
