Message-ID: <56F0C39B.6090802@osg.samsung.com>
Date:	Mon, 21 Mar 2016 22:01:31 -0600
From:	Shuah Khan <shuahkh@....samsung.com>
To:	Mauro Carvalho Chehab <mchehab@....samsung.com>
Cc:	tiwai@...e.com, perex@...ex.cz, linux-media@...r.kernel.org,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH] sound/usb: fix to release stream resources from
 media_snd_device_delete()

On 03/19/2016 07:31 AM, Shuah Khan wrote:
> On 03/19/2016 06:10 AM, Mauro Carvalho Chehab wrote:
>> Em Fri, 18 Mar 2016 20:50:31 -0600
>> Shuah Khan <shuahkh@....samsung.com> escreveu:
>>
>>> Fix to release stream resources from media_snd_device_delete() before
>>> media device is unregistered. Without this change, stream resource free
>>> is attempted after the media device is unregistered which would result
>>> in use-after-free errors.
>>>
>>> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
>>> ---
>>>
>>> - Ran bind/unbind loop (1000 iteration) test on snd-usb-audio
>>>   while running mc_nextgen_test loop (1000 iterations) in parallel.
>>> - Ran bind/unbind and rmmod/modprobe tests on both drivers. Also
>>>   generated graphs when after bind/unbind, rmmod/modprobe. Graphs
>>>   look good.
>>> - Note: Please apply the following patch to fix memory leak:
>>>   sound/usb: Fix memory leak in media_snd_stream_delete() during unbind
>>>   https://lkml.org/lkml/2016/3/16/1050
>>
>> Yeah, a way better!
>>
>> For normal bind/unbind, it seems to be working fine. Also
>> for driver's rmmod, so:
>>
>> Tested-by: Mauro Carvalho Chehab <mchehab@....samsung.com>
>>
>> PS.:
>> ===
>>
>> There are still some troubles if we run an infinite loop
>> binding/unbinding au0828 and another one binding/unbinding
>> snd-usb-audio, like this one:
> 
> Yes. I noticed this one when I was running a loop of 1000 on au0828.
> I couldn't reproduce this when I tested this patch.
> 
> P.S: au08282 loops takes longer btw since au0828 initialization is lot more
> complex. We have to look at this one.
> 
>>
>>
>> [   91.556188] ------------[ cut here ]------------
>> [   91.556500] WARNING: CPU: 1 PID: 2920 at drivers/media/media-entity.c:392 __media_entity_pipeline_start+0x271/0xce0 [media]()
>> [   91.556626] Modules linked in: ir_lirc_codec lirc_dev au8522_dig xc5000 tuner au8522_decoder au8522_common au0828 videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core tveeprom dvb_core rc_core v4l2_common videodev snd_usb_audio snd_usbmidi_lib snd_rawmidi snd_seq_device media cpufreq_powersave cpufreq_conservative cpufreq_userspace cpufreq_stats parport_pc ppdev lp parport snd_hda_codec_hdmi intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel iTCO_wdt kvm iTCO_vendor_support irqbypass crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel sha256_ssse3 sha256_generic hmac drbg snd_hda_codec_realtek i915 snd_hda_codec_generic aesni_intel aes_x86_64 btusb lrw btrtl gf128mul snd_hda_intel glue_helper ablk_helper btbcm btintel cryptd psmouse snd_hda_codec bluetooth
>> [   91.556693]  snd_hwdep i2c_algo_bit sg snd_hda_core serio_raw pcspkr evdev drm_kms_helper snd_pcm rfkill drm snd_timer mei_me snd i2c_i801 soundcore lpc_ich mei mfd_core battery video dw_dmac i2c_designware_platform dw_dmac_core i2c_designware_core acpi_pad button tpm_tis tpm ext4 crc16 mbcache jbd2 dm_mod sd_mod hid_generic usbhid ahci libahci libata e1000e xhci_pci ptp scsi_mod ehci_pci ehci_hcd pps_core xhci_hcd fan thermal sdhci_acpi sdhci mmc_core i2c_hid hid
>> [   91.556748] CPU: 1 PID: 2920 Comm: v4l_id Tainted: G      D W       4.5.0+ #62
>> [   91.556751] Hardware name:                  /NUC5i7RYB, BIOS RYBDWi35.86A.0350.2015.0812.1722 08/12/2015
>> [   91.556754]  ffffffffa0e247a0 ffff8803a3d17b08 ffffffff819447c1 0000000000000000
>> [   91.556759]  ffff88009bbe17c0 ffff8803a3d17b48 ffffffff8114fd16 ffffffffa0e20651
>> [   91.556763]  ffff8803a47c9c58 ffff8803a477d2c8 ffff8803a5ac96f8 dffffc0000000000
>> [   91.556768] Call Trace:
>> [   91.556774]  [<ffffffff819447c1>] dump_stack+0x85/0xc4
>> [   91.556778]  [<ffffffff8114fd16>] warn_slowpath_common+0xc6/0x120
>> [   91.556783]  [<ffffffffa0e20651>] ? __media_entity_pipeline_start+0x271/0xce0 [media]
>> [   91.556786]  [<ffffffff8114feea>] warn_slowpath_null+0x1a/0x20
>> [   91.556790]  [<ffffffffa0e20651>] __media_entity_pipeline_start+0x271/0xce0 [media]
>> [   91.556794]  [<ffffffff822d9aca>] ? __schedule+0x78a/0x2570
>> [   91.556797]  [<ffffffff8156e428>] ? memset+0x28/0x30
>> [   91.556802]  [<ffffffffa0e203e0>] ? media_entity_pipeline_stop+0x60/0x60 [media]
>> [   91.556806]  [<ffffffff8124a73d>] ? trace_hardirqs_on+0xd/0x10
>> [   91.556810]  [<ffffffffa1430a05>] ? au0828_enable_source+0x55/0x9f0 [au0828]
>> [   91.556813]  [<ffffffff822ddb20>] ? mutex_trylock+0x400/0x400
>> [   91.556818]  [<ffffffffa1440833>] ? au0828_v4l2_close+0xb3/0x590 [au0828]
>> [   91.556822]  [<ffffffffa1430da4>] au0828_enable_source+0x3f4/0x9f0 [au0828]
>> [   91.556824]  [<ffffffff822ddb20>] ? mutex_trylock+0x400/0x400
>> [   91.556834]  [<ffffffffa133acf6>] v4l_enable_media_source+0x66/0x90 [videodev]
>> [   91.556839]  [<ffffffffa14409da>] au0828_v4l2_close+0x25a/0x590 [au0828]
>> [   91.556846]  [<ffffffffa1301270>] v4l2_release+0xf0/0x210 [videodev]
>> [   91.556849]  [<ffffffff815c2c4f>] __fput+0x20f/0x6d0
>> [   91.556853]  [<ffffffff815c317e>] ____fput+0xe/0x10
>> [   91.556856]  [<ffffffff811acde7>] task_work_run+0x137/0x200
>> [   91.556859]  [<ffffffff81005d54>] exit_to_usermode_loop+0x154/0x180
>> [   91.556863]  [<ffffffff8124a1b6>] ? trace_hardirqs_on_caller+0x16/0x590
>> [   91.556866]  [<ffffffff810073a6>] syscall_return_slowpath+0x186/0x1c0
>> [   91.556869]  [<ffffffff822e7a1c>] entry_SYSCALL_64_fastpath+0xbf/0xc1
>> [   91.556872] ---[ end trace 3e95e11ff0b9efad ]---
>>
>> I suspect that something is not properly protected by the graph mutex at
>> either ALSA or au0828 driver.
>>
>> I also got a GPF:
>>
>> [   95.398931] au0828: Start Pipeline: Xceive XC5000->au0828a vbi Error -16
>> [   95.398936] au0828: Deactivate link Error 0
>> [   95.398943] tuner 6-0061: Putting tuner to sleep
>> [   95.398960] kasan: CONFIG_KASAN_INLINE enabled
>> [   95.398962] kasan: GPF could be caused by NULL-ptr deref or user memory access
>> [   95.398967] general protection fault: 0000 [#2] SMP KASAN
>> [   95.399020] Modules linked in: ir_lirc_codec lirc_dev au8522_dig xc5000 tuner au8522_decoder au8522_common au0828 videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core tveeprom dvb_core rc_core v4l2_common videodev snd_usb_audio snd_usbmidi_lib snd_rawmidi snd_seq_device media cpufreq_powersave cpufreq_conservative cpufreq_userspace cpufreq_stats parport_pc ppdev lp parport snd_hda_codec_hdmi intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel iTCO_wdt kvm iTCO_vendor_support irqbypass crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel sha256_ssse3 sha256_generic hmac drbg snd_hda_codec_realtek i915 snd_hda_codec_generic aesni_intel aes_x86_64 btusb lrw btrtl gf128mul snd_hda_intel glue_helper ablk_helper btbcm btintel cryptd psmouse snd_hda_codec bluetooth
>> [   95.399853]  snd_hwdep i2c_algo_bit sg snd_hda_core serio_raw pcspkr evdev drm_kms_helper snd_pcm rfkill drm snd_timer mei_me snd i2c_i801 soundcore lpc_ich mei mfd_core battery video dw_dmac i2c_designware_platform dw_dmac_core i2c_designware_core acpi_pad button tpm_tis tpm ext4 crc16 mbcache jbd2 dm_mod sd_mod hid_generic usbhid ahci libahci libata e1000e xhci_pci ptp scsi_mod ehci_pci ehci_hcd pps_core xhci_hcd fan thermal sdhci_acpi sdhci mmc_core i2c_hid hid
>> [   95.400389] CPU: 2 PID: 2966 Comm: v4l_id Tainted: G      D W       4.5.0+ #62
>> [   95.400455] Hardware name:                  /NUC5i7RYB, BIOS RYBDWi35.86A.0350.2015.0812.1722 08/12/2015
>> [   95.400541] task: ffff88009bbe4740 ti: ffff8803a45a0000 task.ti: ffff8803a45a0000
>> [   95.400610] RIP: 0010:[<ffffffff81db0aa4>]  [<ffffffff81db0aa4>] usb_set_interface+0x34/0x9c0
>> [   95.400694] RSP: 0018:ffff8803a45a7d18  EFLAGS: 00010202
>> [   95.400744] RAX: dffffc0000000000 RBX: ffff8803a3cbab2c RCX: 1ffff10006ba18e2
>> [   95.400809] RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000000040
>> [   95.400873] RBP: ffff8803a45a7d88 R08: 0000000000000001 R09: 0000000000000001
>> [   95.400938] R10: ffff8803a4414a38 R11: 0000000000000000 R12: ffff8803bc482400
>> [   95.401004] R13: dffffc0000000000 R14: ffff8803a3cb8000 R15: 0000000000000000
>> [   95.401069] FS:  00007f19fbd19700(0000) GS:ffff8803c6900000(0000) knlGS:0000000000000000
>> [   95.401141] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [   95.401190] CR2: 0000558300d51d44 CR3: 000000009af29000 CR4: 00000000003406e0
>> [   95.401255] Stack:
>> [   95.401277]  ffff8803a5b5ea20 ffff8803a45a7d40 ffffffffa1490f0f 0000000000000061
>> [   95.401358]  ffff8803a5b5e510 ffff8803a45a7d58 ffffffffa147003c ffff880300000000
>> [   95.401438]  ffff880300000000 ffff8803a3cbab2c ffff8803bc482400 dffffc0000000000
>> [   95.401518] Call Trace:
>> [   95.401547]  [<ffffffffa1490f0f>] ? xc5000_sleep+0x8f/0xd0 [xc5000]
>> [   95.405722]  [<ffffffffa147003c>] ? fe_standby+0x3c/0x50 [tuner]
>> [   95.409842]  [<ffffffffa1440b20>] au0828_v4l2_close+0x3a0/0x590 [au0828]
>> [   95.412140]  [<ffffffffa1301270>] v4l2_release+0xf0/0x210 [videodev]
>> [   95.414119]  [<ffffffff815c2c4f>] __fput+0x20f/0x6d0
>> [   95.416046]  [<ffffffff815c317e>] ____fput+0xe/0x10
>> [   95.417879]  [<ffffffff811acde7>] task_work_run+0x137/0x200
>> [   95.419656]  [<ffffffff81005d54>] exit_to_usermode_loop+0x154/0x180
>> [   95.421420]  [<ffffffff8124a1b6>] ? trace_hardirqs_on_caller+0x16/0x590
>> [   95.423177]  [<ffffffff810073a6>] syscall_return_slowpath+0x186/0x1c0
>> [   95.424911]  [<ffffffff822e7a1c>] entry_SYSCALL_64_fastpath+0xbf/0xc1
>> [   95.426629] Code: 00 00 00 00 fc ff df 48 89 e5 41 57 41 56 41 55 41 54 49 89 ff 53 48 83 c7 40 48 83 ec 48 89 55 c8 48 89 fa 48 c1 ea 03 89 75 d0 <80> 3c 02 00 0f 85 67 07 00 00 49 8d 7f 18 48 b8 00 00 00 00 00 
>> [   95.428560] RIP  [<ffffffff81db0aa4>] usb_set_interface+0x34/0x9c0
>> [   95.430358]  RSP <ffff8803a45a7d18>
>> [   95.432566] ---[ end trace 3e95e11ff0b9efaf ]---
>>
>> As nobody expects someone to do infinite loops binding/unbinding
>> both drivers, I guess it is ok to keep it for Kernel 4.6, but
>> we need to find a way fix those locking issues for dynamic graph
>> changes.
>>
> 
> Yes. Right. We have to look at these closely. I agree nobody runs a stress
> bin/ubind and rmmod/modprobe like we are doing. I think there is some lock
> and race type issue in au0828 v4l2 release path. I have had to fix some issues
> there in the past. I agree with you that we are good for 4.6-rc1 and I can 
> continue to look at this. We can get this fixed for rc2 or rc3.
> 

I isolated this problem to an existing race condition between au0828_v4l2_open()
and  au0828_v4l2_close(). It won't show up in normal scenarios. The bind/unbind
loop test triggers it.

au0828_v4l2_close() check for dev_state == DEV_DISCONNECTED will fail to
detect the device disconnected state correctly, if au0828_v4l2_open() runs
to set the DEV_INITIALIZED bit. A loop test of bind/unbind found this bug
by increasing the likelihood of au0828_v4l2_open() occurring while unbind
is in progress. When au0828_v4l2_close() fails to detect that the device
is in disconnect state, it attempts to power down the device and fails with
the both of the above problems.

The second one from xc5000_sleep() would trigger without any of the new
patches. I am building Linux 4.5 to verify that.

I am sending one line fix patch. I ran the loop test 1000 times and didn't
see the above two issues.

thanks,
-- Shuah

-- 
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@....samsung.com | (970) 217-8978

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