[alsa-devel] snd_device_name_hint segfaults

[Forest Bond]

Hi,

I'm seeing segfaults with VLC similar to those reported here:

  http://mailman.alsa-project.org/pipermail/alsa-devel/2013-January/059168.html

This is on Ubuntu 12.04 with the latest alsa-lib package (1.0.25-1ubuntu10.2)
and the following patches also applied:

* 2cfc8b9b44a8e493c41b3d63d5a00b306a18a5ed
  snd_pcm_direct_parse_open_conf(): use thread-safe getgrnam_r()
* 44c1a623dd1fc9e831616b663bebc54ca98df994
  Add snd_lib_error_set_local() to install a thread-local error handler.
* 25dbb102810b31c02358904d70d53c960fb0a10e
  snd_device_name_hint(): do not change the global error handler.
* f49b2dc522a2564315c76d075203b15a39941e8a
  snd_device_name_hint(): do not use global snd_config.
* 7f2b2c8c1650a1883b48abfcdb455138943854f9
  conf: Fix a memory access violation resulting from improper error propogation

So I think there are still issues when calling snd_device_name_hint(-1, ...).

Here is the backtrace:

#0  0x003f0e78 in __strcpy_chk () from /lib/i386-linux-gnu/libc.so.6
#1  0x0625084b in strcpy (__src=0x0, __dest=0xb6025e80 "pcm.(null)") at /usr/include/i386-li
nux-gnu/bits/string3.h:105
#2  try_config (config=0xaf1c4df0, list=0xb52fe804, base=0x323e962 "pcm", name=0x0) at nameh
int.c:243
#3  0x06251bc5 in add_software_devices (list=0xb52fe804, config=0xaf1c4df0) at namehint.c:51
2
#4  snd_device_name_hint (card=-1, iface=<optimized out>, hints=0xb52fe90c) at namehint.c:59
1
#5  0x0323c9bb in GetDevices (obj=0xb6271700, item=0x0, prefs_dev=<optimized out>) at alsa.c
:721
#6  0x0323d4c0 in Probe (dev=0xb6011df8 "default", obj=0xb6271700) at alsa.c:161
#7  Open (obj=0xb6271700) at alsa.c:539
#8  0x0a6c73d0 in generic_start (func=0x323cd10, ap=0xb52fed98 "\273") at modules/modules.c:422
#9  0x0a6c7a3a in vlc_module_load (p_this=0xb6271700, psz_capability=0xa70b959 "audio output", psz_name=<optimized out>, b_strict=false,
    probe=0xa6c73c0 <generic_start>) at modules/modules.c:347
#10 0x0a6c8002 in module_need (obj=0xb6271700, cap=0xa70b959 "audio output", name=0xa70d2bd "$aout", strict=false) at modules/modules.c:437
#11 0x0a6b1242 in aout_OutputNew (p_aout=0xb6271700, p_format=0xb52feeac) at audio_output/output.c:59
#12 0x0a6ad77f in aout_DecNew (p_aout=0xb6271700, p_format=0xb52feeac, p_replay_gain=0xaef02a14, p_request_vout=0xb52feed0)
    at audio_output/dec.c:112
#13 0x0a67066e in aout_new_buffer (p_dec=0xaef02870, i_samples=1024) at input/decoder.c:2286
#14 0x0a672690 in decoder_NewAudioBuffer (p_decoder=0xaef02870, i_size=1024) at input/decoder.c:213
#15 0x04032f8c in DecodeBlock (p_dec=0xaef02870, pp_block=0xb52ff05c) at faad.c:464
#16 0x0a670891 in DecoderDecodeAudio (p_dec=0xaef02870, p_block=0xaef03000) at input/decoder.c:1291
#17 0x0a6716f5 in DecoderProcessAudio (b_flush=false, p_block=0xaef03000, p_dec=0xaef02870) at input/decoder.c:1936
#18 DecoderProcess (p_dec=0xaef02870, p_block=<optimized out>) at input/decoder.c:2059
#19 0x0a671959 in DecoderThread (p_data=0xaef02870) at input/decoder.c:938
#20 0x001fbd4c in start_thread () from /lib/i386-linux-gnu/libpthread.so.0
#21 0x003ddace in clone () from /lib/i386-linux-gnu/libc.so.6

As a work around I will probably patch VLC to not call snd_device_name_hint this
way.  I see this has been done for other applications:

http://code.google.com/p/chromium/issues/detail?id=95797
http://code.mythtv.org/trac/ticket/10809

But I wanted to try diagnosing the issue first.  Thoughts?

Thanks,
Forest
-- 
Forest Bond
http://www.alittletooquiet.net
http://www.rapidrollout.com
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