[alsa-devel] [PATCH v2] ALSA: ASoC: soc-compress.c: fix NULL dereference

[Qais Yousef]

On 01/13/2015 02:59 PM, Vinod Koul wrote:
> On Tue, Jan 13, 2015 at 11:18:53AM +0000, Qais Yousef wrote:
>> In soc_new_compress() when rtd->dai_link->daynmic is set, we create the pcm
> 					   ^^^^^^^^
> typo
>> substreams with this call:
>>
>>     ret = snd_pcm_new_internal(rtd->card->snd_card, new_name, num,
>>                                     1, 0, &be_pcm);
>>
>> which passes 0 as capture_count leading to
>>
>>     be_pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream
>>
>> being NULL, hence when trying to set rtd a few lines below we get an oops.
> It is a good practice to add the oops here

Will this really be helpful? I think it'll be more clutter (the 
backtrace on metag arch is not great):

Oops: err 8007 (Unknown fault) addr 00000008 [#1]
  Modules linked in:
  CPU: 0 PID: 6 Comm: kworker/u2:0 Not tainted 3.18.0-rc4+ #1904
  Workqueue: deferwq _deferred_probe_work_func
  task: 4f030780 ti: 4f044000 task.ti: 4f044000
   pt_regs @ 4f044388
   SaveMask = 0x4041
   Flags = 0x0008 (Znoc)
   TXRPT = 0x00000000
   PC = 0x402e6c58
   A0StP = 0x4f044388     A1GbP = 0x60001000
   A0FrP = 0x4f044110     A1LbP = 0x40000048
   A0.2  = 0x00000000     A1.2  = 0x00000000
   A0.3  = 0x40090000     A1.3  = 0x00000001
   D0Re0 = 0x00000000     D1Re0 = 0x00000001
   D0Ar6 = 0x00000000     D1Ar5 = 0x4b5c1a00
   D0Ar4 = 0x4f044330     D1Ar3 = 0x405833a8
   D0Ar2 = 0x4f1d7170     D1Ar1 = 0x4b5c25a0
   D0FrT = 0x00000001     D1RtP = 0x402e6c20
   D0.5  = 0x00000000     D1.5  = 0x4f1f65c4
   D0.6  = 0x4f1f65c4     D1.6  = 0x4f1d0500
   D0.7  = 0x00000001     D1.7  = 0x4f1e3e40

  Call trace:
  [<40410004>] _ieee80211_change_bss+0x1b4/0x220
  [<400f8034>] _kernfs_add_one+0x10c/0x17c
  [<400fa2b0>] ___kernfs_create_file+0x94/0xdc
  [<402d8bf0>] _snd_soc_register_card+0x12b8/0x1380
  [<400170e8>] ___request_region+0x58/0x150
  [<402068b4>] _devres_add+0x14/0x2c
  [<402e97f0>] _zero1xx_probe+0x2b8/0x37c
  [<40205004>] _platform_drv_probe+0x4c/0xc0
  [<40204fb4>] _platform_drv_remove+0x3c/0x40
  [<402032e0>] _driver_probe_device+0xc8/0x294
  [<40204fb4>] _platform_drv_remove+0x3c/0x40
  [<40203624>] _wait_for_device_probe+0x7c/0x80
  [<40201cac>] _bus_for_each_drv+0x5c/0xb0
  [<40203708>] _device_attach+0x84/0x9c
  [<40202258>] _bus_probe_device+0x90/0xd0
  [<4020354c>] _deferred_probe_work_func+0x70/0xac
  [<40025d84>] _process_one_work+0x110/0x364
  [<402034d8>] _device_bind_driver+0x2c/0x30
  [<40046150>] _mod_timer+0xc4/0x178
  [<400286a4>] _worker_thread+0x14c/0x4d4
  [<4002b90c>] _kthread_parkme+0x14/0x18
  [<40028554>] _pool_mayday_timeout+0xe8/0xec
  [<4002ba08>] _kthread+0xf8/0x100
  [<4000aeb4>] _ret_from_fork+0x44/0x110
  [<4002b90c>] _kthread_parkme+0x14/0x18
  [<40000044>] _text+0x44/0x48
  [<40000044>] _text+0x44/0x48
  [<4002b90c>] _kthread_parkme+0x14/0x18

  Process: kworker/u2:0 (pid: 6, stack limit = 4f046000)
  ---[ end trace fabdbb359f5c60d8 ]---

>
>> Fix by using rtd->dai_link->dpcm_playback and rtd->dai_link->dpcm_capture as
>> playback_count and capture_count to snd_pcm_new_internal().
>>
>> Signed-off-by: Qais Yousef <qais.yousef at imgtec.com>
>> Cc: Vinod Koul <vinod.koul at intel.com>
>> Cc: Liam Girdwood <lgirdwood at gmail.com>
>> Cc: Mark Brown <broonie at kernel.org>
>> Cc: Jaroslav Kysela <perex at perex.cz>
>> Cc: Takashi Iwai <tiwai at suse.de>
>> Cc: linux-kernel at vger.kernel.org
>> ---
>> v2->v1:
>>     - use better way to fix it than just removing the line that caused the oops
>>
>>   sound/soc/soc-compress.c | 9 ++++++---
>>   1 file changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/sound/soc/soc-compress.c b/sound/soc/soc-compress.c
>> index 590a82f01d0b..27a668463ad7 100644
>> --- a/sound/soc/soc-compress.c
>> +++ b/sound/soc/soc-compress.c
>> @@ -659,7 +659,8 @@ int soc_new_compress(struct snd_soc_pcm_runtime *rtd, int num)
>>   			rtd->dai_link->stream_name);
>>   
>>   		ret = snd_pcm_new_internal(rtd->card->snd_card, new_name, num,
>> -				1, 0, &be_pcm);
>> +				rtd->dai_link->dpcm_playback,
>> +				rtd->dai_link->dpcm_capture, &be_pcm);
>>   		if (ret < 0) {
>>   			dev_err(rtd->card->dev, "ASoC: can't create compressed for %s\n",
>>   				rtd->dai_link->name);
>> @@ -668,8 +669,10 @@ int soc_new_compress(struct snd_soc_pcm_runtime *rtd, int num)
>>   
>>   		rtd->pcm = be_pcm;
>>   		rtd->fe_compr = 1;
>> -		be_pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream->private_data = rtd;
>> -		be_pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream->private_data = rtd;
>> +		if (rtd->dai_link->dpcm_playback)
>> +			be_pcm->streams[SNDRV_PCM_STREAM_PLAYBACK].substream->private_data = rtd;
>> +		if (rtd->dai_link->dpcm_capture)
> this should be else if, as for compressed device we can have playback or
> capture not both
>
>> +			be_pcm->streams[SNDRV_PCM_STREAM_CAPTURE].substream->private_data = rtd;
>>   		memcpy(compr->ops, &soc_compr_dyn_ops, sizeof(soc_compr_dyn_ops));
>>   	} else
>>   		memcpy(compr->ops, &soc_compr_ops, sizeof(soc_compr_ops));
>> -- 
>> 2.1.0
>>