On 17.10.2016 15:44, James Almer wrote:
> On 10/17/2016 4:47 AM, Benoit Fouet wrote:
>> On 17/10/2016 06:49, James Almer wrote:
>>> On 10/16/2016 9:30 PM, James Almer wrote:
>>>> On 10/16/2016 5:11 PM, Andreas Cadhalpun wrote:
>>>>> The problem was introduced in commit 1273bc6.
>>>>>
>>>>> Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
>>>>> ---
>>>>> libavformat/matroskadec.c | 2 +-
>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
>>>>> index 8847c62..a5d3c0e 100644
>>>>> --- a/libavformat/matroskadec.c
>>>>> +++ b/libavformat/matroskadec.c
>>>>> @@ -1759,7 +1759,7 @@ static int mkv_field_order(MatroskaDemuxContext
>>>>> *matroska, int64_t field_order)
>>>>> /* workaround a bug in our Matroska muxer, introduced in version
>>>>> 57.36 alongside
>>>>> * this function, and fixed in 57.52 */
>>>>> - if (sscanf(matroska->muxingapp, "Lavf%d.%d.%d", &major, &minor,
>>>>> µ) == 3)
>>>>> + if (matroska->muxingapp && sscanf(matroska->muxingapp,
>>>>> "Lavf%d.%d.%d", &major, &minor, µ) == 3)
>>>> LGTM.
>>>>
>>>> Matroska files are supposed to always have that element, but even ffmpeg
>>>> used
>>>> to mux files without it at some point when bitexact flag was enabled, so i
>>>> guess plenty of files out there are missing it.
>>>>
>>>>> bttb = (major == 57 && minor >= 36 && minor <= 51 && micro >=
>>>>> 100);
>>>>> switch (field_order) {
>>>>>
>>> Just tried a file missing the muxingapp element, meaning matroska->muxingapp
>>> is NULL, and sscanf simply returns -1 and sets errno to EINVAL.
>>>
>>> Where does it crash for you and using what file?
>>
>> FWIW, I've just written a quick test on my machine, and an "sscanf(NULL,
>> "%d", &i)" segfaults.
With glibc it crashes:
$ gdb --batch -ex r -ex bt -ex q --args ./ffmpeg_g -i
./id_b42167853bffe74a3a93ea312837dd8a2a25a951.matroska -f null /dev/null
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
ffmpeg version N-82012-gd3874b7 Copyright (c) 2000-2016 the FFmpeg developers
built with gcc 6.2.0 (Debian 6.2.0-6) 20161010
configuration: --disable-optimizations
libavutil 55. 32.100 / 55. 32.100
libavcodec 57. 61.103 / 57. 61.103
libavformat 57. 52.100 / 57. 52.100
libavdevice 57. 0.102 / 57. 0.102
libavfilter 6. 64.100 / 6. 64.100
libswscale 4. 1.100 / 4. 1.100
libswresample 2. 2.100 / 2. 2.100
[matroska,webm @ 0x2380fc0] Unknown EBML doctype 'ma@roUka'
Truncating packet of size 134217728 to 1551
Truncating packet of size 1431346 to 1507
Truncating packet of size 4467 to 1401
[matroska,webm @ 0x2380fc0] Duplicate element
[matroska,webm @ 0x2380fc0] Unknown/unsupported AVCodecID ��OPU=.
Ignoring attempt to set invalid timebase 0/1 for st:0
Program received signal SIGSEGV, Segmentation fault.
rawmemchr () at ../sysdeps/x86_64/rawmemchr.S:37
37 ../sysdeps/x86_64/rawmemchr.S: Datei oder Verzeichnis nicht gefunden.
#0 rawmemchr () at ../sysdeps/x86_64/rawmemchr.S:37
#1 0x00007ffff4b383a2 in _IO_str_init_static_internal
(sf=sf@entry=0x7fffffffd360, ptr=ptr@entry=0x0, size=size@entry=0,
pstart=pstart@entry=0x0) at strops.c:41
#2 0x00007ffff4b27567 in __GI___isoc99_vsscanf (string=0x0, format=0x15e597c
"Lavf%d.%d.%d", args=args@entry=0x7fffffffd488) at isoc99_vsscanf.c:41
#3 0x00007ffff4b27507 in __isoc99_sscanf (s=<optimized out>, format=<optimized
out>) at isoc99_sscanf.c:31
#4 0x00000000006ca2eb in mkv_field_order (matroska=0x2381ba0, field_order=2)
at src/libavformat/matroskadec.c:1762
#5 0x00000000006cc0c2 in matroska_parse_tracks (s=0x2380fc0) at
src/libavformat/matroskadec.c:2293
#6 0x00000000006ccc83 in matroska_read_header (s=0x2380fc0) at
src/libavformat/matroskadec.c:2470
#7 0x00000000007bbd13 in avformat_open_input (ps=0x7fffffffd948,
filename=0x7fffffffe3a4
"./id_b42167853bffe74a3a93ea312837dd8a2a25a951.matroska", fmt=0x0,
options=0x2380d68) at src/libavformat/utils.c:587
#8 0x0000000000411aeb in open_input_file (o=0x7fffffffda50,
filename=0x7fffffffe3a4
"./id_b42167853bffe74a3a93ea312837dd8a2a25a951.matroska") at
src/ffmpeg_opt.c:997
#9 0x000000000041a9af in open_files (l=0x2380c98, inout=0x154c797 "input",
open_file=0x411330 <open_input_file>) at src/ffmpeg_opt.c:3135
#10 0x000000000041ab10 in ffmpeg_parse_options (argc=6, argv=0x7fffffffe048) at
src/ffmpeg_opt.c:3175
#11 0x000000000042e78a in main (argc=6, argv=0x7fffffffe048) at
src/ffmpeg.c:4564
> Guess it's up to the implementation, then. I tried with mingw-w64 only.
> The documentation for sscanf says it sets errno to EINVAL if *format is NULL,
> but doesn't mention *str.
>
> Patch still LGTM. It doesn't hurt either way.
Pushed.
Best regards,
Andreas
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