Segfault after video open error

[jonnor]

Happened on 2 out of 2 .mp4 files. Probably x264 encoded.

Expected: to get a helpful error message, and no crash.
Got: a quite uninformative error, and segfault.

Should possibly be fixed in GEGL, idk. In general we don't have a very good mechanism to report error and let consuming applications catch it? Hit that issue also in imgflo

Stacktrace attached.

[jon@jon-laptop iconographer]$ gdb --args ./iconographer ./kdenlive/printed-electret-microphone.mp4
GNU gdb (GDB) 7.10
...
Reading symbols from ./iconographer...done.
(gdb) y
Undefined command: "y".  Try "help".
(gdb) r
Starting program: /home/jon/contrib/code/iconographer/iconographer ./kdenlive/printed-electret-microphone.mp4
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
Failed to release test userptr object! (9) i915 kernel driver may not be sane!
Failed to release test userptr object! (9) i915 kernel driver may not be sane!
Failed to release test userptr object! (9) i915 kernel driver may not be sane!

(iconographer:2360): GEGL-ff-load.c-WARNING **: ./kdenlive/printed-electret-microphone.mp4: Error while opening file


Program received signal SIGSEGV, Segmentation fault.
0x00007fffd541550d in prepare (operation=0x1256190) at ff-load.c:396
396       fprintf (stderr, "[%lu]\n", p->video_fcontext->start_time_realtime);
(gdb) print p
$1 = (Priv *) 0x12a5e80
(gdb) print *p
$2 = {width = 320, height = 200, fps = 0, loadedfilename = 0x0, audio_fcontext = 0x0, audio_codec = 0x0, audio_index = 0, audio_track = 0x0, audio_cursor_pos = 0, audio_pos = 0, 
  prevapts = 0, a_prevframe = 0, video_fcontext = 0x0, video_index = 0, video_stream = 0x0, audio_stream = 0x0, video_codec = 0x0, lavc_frame = 0x0, prevframe = 0, prevpts = 0}
(gdb) 

[jonnor]

This crash also happens on entirely invalid data.

[jon@jon-laptop iconographer]$ touch zerobytes.mp4
[jon@jon-laptop iconographer]$ gdb --args ./iconographer zerobytes.mp4 
...
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x12a5ee0] Format mov,mp4,m4a,3gp,3g2,mj2 detected only with low score of 1, misdetection possible!
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x12a5ee0] moov atom not found
...
(iconographer:2950): GEGL-ff-load.c-WARNING **: zerobytes.mp4: Error while parsing header or unknown format

Program received signal SIGSEGV, Segmentation fault.
0x00007fffd541550d in prepare (operation=0x1256190) at ff-load.c:396
396       fprintf (stderr, "[%lu]\n", p->video_fcontext->start_time_realtime);

[jonnor]

Here is the failing MP4 file: ftp://vps.jonnor.com/imgflo/printed-electret-microphone.mp4

[jonnor]

Turns out for that MP4 I was just inputting the wrong path. Bug still stands though, should not crash, and error message should be more helpful.