[FFmpeg-devel] [PATCH]lavf/mov: Do not blindly allocate stts entries

[Carl Eugen Hoyos]

2017-12-31 22:17 GMT+01:00 Michael Niedermayer <michael at niedermayer.cc>:
> On Sat, Dec 30, 2017 at 02:36:39PM +0100, Carl Eugen Hoyos wrote:
>> 2017-12-29 23:37 GMT+01:00 Carl Eugen Hoyos <ceffmpeg at gmail.com>:
>> > 2017-11-28 21:32 GMT+01:00 Michael Niedermayer <michael at niedermayer.cc>:
>> >> On Mon, Nov 27, 2017 at 05:24:14AM +0100, Carl Eugen Hoyos wrote:
>> >
>> >>>      for (i = 0; i < entries && !pb->eof_reached; i++) {
>> >>> -        int sample_duration;
>> >>> +        int sample_duration, ret;
>> >>>          unsigned int sample_count;
>> >>> +        if (i > sc->stts_count) {
>> >>> +            ret = av_reallocp_array(&sc->stts_data,
>> >>> +                                    FFMIN(sc->stts_count * 2LL, entries),
>> >>> +                                    sizeof(*sc->stts_data));
>> >>
>> >> this should use a variant of av_fast_realloc
>> >
>> > Do you prefer the new patch?
>> > The old variant here looks slightly saner to me.
>>
>> Attached is what you possibly had in mind.
>>
>> Please review, Carl Eugen
>
>>  mov.c |   13 +++++++++++--
>>  1 file changed, 11 insertions(+), 2 deletions(-)
>> cc7986179fe0ddc394457e8543d9ae907b49373c  0001-lavf-mov-Use-av_fast_realloc-in-mov_read_stts.patch
>> From f5fcd9ed1e5ce604c358a3787f1977277005ebb5 Mon Sep 17 00:00:00 2001
>> From: Carl Eugen Hoyos <ceffmpeg at gmail.com>
>> Date: Sat, 30 Dec 2017 14:34:41 +0100
>> Subject: [PATCH] lavf/mov: Use av_fast_realloc() in mov_read_stts().
>>
>> Avoids large allocations for short files with invalid stts entry.
>> Fixes bugzilla 1102.
>> ---
>>  libavformat/mov.c |   13 +++++++++++--
>>  1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index 2064473..1e97652 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -2850,13 +2850,22 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>          av_log(c->fc, AV_LOG_WARNING, "Duplicated STTS atom\n");
>>      av_free(sc->stts_data);
>>      sc->stts_count = 0;
>> -    sc->stts_data = av_malloc_array(entries, sizeof(*sc->stts_data));
>> -    if (!sc->stts_data)
>> +    if (entries >= INT_MAX / sizeof(*sc->stts_data))
>>          return AVERROR(ENOMEM);
>
> this leaves a stale pointer on error in sc->stts_data

New patch attached.

Thank you, Carl Eugen
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-lavf-mov-Use-av_fast_realloc-in-mov_read_stts.patch
Type: text/x-patch
Size: 1679 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20171231/9985c518/attachment.bin>