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

[Carl Eugen Hoyos]

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:
>> Hi!
>>
>> Attached patch avoids allocations >1GB for (short and) invalid mov
>> files with only reasonable speed impact.
>>
>> Please review, Carl Eugen
>
>>  mov.c |   16 +++++++++++++---
>>  1 file changed, 13 insertions(+), 3 deletions(-)
>> 980861e4c47c80c850d4e849043df2510a3d1d32  0001-lavf-mov-Do-not-blindly-allocate-huge-memory-blocks-.patch
>> From 0d243bad5fdd9850ff41d49a32a06274a3cd9756 Mon Sep 17 00:00:00 2001
>> From: Carl Eugen Hoyos <ceffmpeg at gmail.com>
>> Date: Mon, 27 Nov 2017 05:13:25 +0100
>> Subject: [PATCH] lavf/mov: Do not blindly allocate huge memory blocks for
>>  stts entries.
>>
>> Fixes large allocations for short files with invalid stts entry.
>> Fixes bugzilla 1102.
>> ---
>>  libavformat/mov.c |   16 +++++++++++++---
>>  1 file changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index ddb1e59..9d353bf 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -2838,14 +2838,24 @@ static int mov_read_stts(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>      if (sc->stts_data)
>>          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));
>> +    sc->stts_count = FFMIN(1024 * 1024, entries);
>> +    sc->stts_data = av_realloc_array(NULL, sc->stts_count, sizeof(*sc->stts_data));
>>      if (!sc->stts_data)
>>          return AVERROR(ENOMEM);
>
> i dont know if leaving stts_count random on return is a good idea

Fixed.

>>      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

New patch attached, only tested with fate.

Thank you, Carl Eugen
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