On 2016/4/6 19:37, Baozeng Ding wrote:
>
>
> On 2016/4/5 22:18, Takashi Iwai wrote:
>> On Tue, 05 Apr 2016 15:51:30 +0200,
>> Baozeng Ding wrote:
>>> Hi all,
>>> I've got the following report (use-after-free in kill_fasync) while
>>> running syzkaller.
>>> Unfortunately no reproducer.The kernel version is 4.5 (on Mar 16 commit
>>> 09fd671ccb2475436bd5f597f751ca4a7d177aea).
>>>
>>> ==================================================================
>>> BUG: KASAN: use-after-free in kill_fasync+0x3fb/0x420 at addr
>>> ffff880067691d88
>>> Read of size 8 by task swapper/2/0
>>> =============================================================================
>>>
>>> BUG kmalloc-2048 (Not tainted): kasan: bad access detected
>>> -----------------------------------------------------------------------------
>>>
>>>
>>> Disabling lock debugging due to kernel taint
>>> INFO: Allocated in 0xbbbbbbbbbbbbbbbb age=18446678412249576073
>>> cpu=2245704320 pid=-1
>>> [< inline >] kmalloc /kernel/include/linux/slab.h:472
>>> [< inline >] kzalloc /kernel/include/linux/slab.h:616
>>> [< none >] snd_pcm_attach_substream+0x3b4/0xb10
>>> /kernel/sound/core/pcm.c:966
>>> [< none >] ___slab_alloc+0x4c7/0x500 /kernel/mm/slub.c:2446
>>> [< none >] __slab_alloc+0x4c/0x90 /kernel/mm/slub.c:2475
>>> [< inline >] slab_alloc_node /kernel/mm/slub.c:2538
>>> [< inline >] slab_alloc /kernel/mm/slub.c:2580
>>> [< none >] kmem_cache_alloc_trace+0x262/0x300
>>> /kernel/mm/slub.c:2597
>>> [< inline >] kmalloc /kernel/include/linux/slab.h:472
>>> [< inline >] kzalloc /kernel/include/linux/slab.h:616
>>> [< none >] snd_pcm_attach_substream+0x3b4/0xb10
>>> /kernel/sound/core/pcm.c:966
>>> [< none >] snd_pcm_open_substream+0x84/0x450
>>> /kernel/sound/core/pcm_native.c:2262
>>> [< inline >] snd_pcm_oss_open_file
>>> /kernel/sound/core/oss/pcm_oss.c:2346
>>> [< none >] snd_pcm_oss_open.part.17+0x5a4/0x1100
>>> /kernel/sound/core/oss/pcm_oss.c:2428
>>> [< none >] snd_pcm_oss_open+0x35/0x50
>>> /kernel/sound/core/oss/pcm_oss.c:2392
>>> [< none >] soundcore_open+0x30f/0x640
>>> /kernel/sound/sound_core.c:639
>>> [< none >] chrdev_open+0x22a/0x4c0 /kernel/fs/char_dev.c:388
>>> [< none >] do_dentry_open+0x6a2/0xcb0 /kernel/fs/open.c:736
>>> [< none >] vfs_open+0x17b/0x1f0 /kernel/fs/open.c:853
>>> [< inline >] do_last /kernel/fs/namei.c:3258
>>> [< none >] path_openat+0x4837/0x5830 /kernel/fs/namei.c:3394
>>> [< none >] do_filp_open+0x18e/0x250 /kernel/fs/namei.c:3429
>>> [< none >] do_sys_open+0x201/0x420 /kernel/fs/open.c:1022
>>> [< inline >] SYSC_open /kernel/fs/open.c:1040
>>> [< none >] SyS_open+0x2d/0x40 /kernel/fs/open.c:1035
>>> INFO: Freed in 0x10000b076 age=18446678416544543380 cpu=0 pid=0
>>> [< none >] snd_pcm_detach_substream+0x134/0x280
>>> /kernel/sound/core/pcm.c:1017
>>> [< none >] __slab_free+0x1e8/0x300 /kernel/mm/slub.c:2657
>>> [< inline >] slab_free /kernel/mm/slub.c:2810
>>> [< none >] kfree+0x24e/0x2d0 /kernel/mm/slub.c:3661
>>> [< none >] snd_pcm_detach_substream+0x134/0x280
>>> /kernel/sound/core/pcm.c:1017
>>> [< none >] snd_pcm_release_substream.part.38+0x219/0x2f0
>>> /kernel/sound/core/pcm_native.c:2250
>>> [< none >] snd_pcm_release_substream+0x59/0x70
>>> /kernel/sound/core/pcm_native.c:2251
>>> [< none >] snd_pcm_oss_release_file+0x45/0xb0
>>> /kernel/sound/core/oss/pcm_oss.c:2305
>>> [< none >] snd_pcm_oss_release+0xfa/0x250
>>> /kernel/sound/core/oss/pcm_oss.c:2485
>>> [< none >] __fput+0x236/0x780 /kernel/fs/file_table.c:208
>>> [< none >] ____fput+0x15/0x20 /kernel/fs/file_table.c:244
>>> [< none >] task_work_run+0x16b/0x200
>>> /kernel/kernel/task_work.c:115
>>> [< inline >] exit_task_work
>>> /kernel/include/linux/task_work.h:21
>>> [< none >] do_exit+0x87f/0x2c90 /kernel/kernel/exit.c:748
>>> [< none >] do_group_exit+0x108/0x330
>>> /kernel/kernel/exit.c:878
>>> [< inline >] SYSC_exit_group /kernel/kernel/exit.c:889
>>> [< none >] SyS_exit_group+0x1d/0x20 /kernel/kernel/exit.c:887
>>> [< none >] entry_SYSCALL_64_fastpath+0x23/0xc1
>>> /kernel/arch/x86/entry/entry_64.S:207
>>> INFO: Slab 0xffffea00019da400 objects=13 used=8 fp=0xffff880067691be0
>>> flags=0x5fffc0000004080
>>> INFO: Object 0xffff880067691bd8 @offset=7128 fp=0xbbbbbbbbbbbbbbbb
>>> Call Trace:
>>> <IRQ> [< inline >] __dump_stack /kernel/lib/dump_stack.c:15
>>> <IRQ> [<ffffffff82945051>] dump_stack+0xb3/0x112
>>> /kernel/lib/dump_stack.c:51
>>> [<ffffffff817009ad>] print_trailer+0x10d/0x190 /kernel/mm/slub.c:668
>>> [<ffffffff817074af>] object_err+0x2f/0x40 /kernel/mm/slub.c:675
>>> [< inline >] print_address_description
>>> /kernel/mm/kasan/report.c:138
>>> [<ffffffff81709ca5>] kasan_report_error+0x215/0x530
>>> /kernel/mm/kasan/report.c:236
>>> [< inline >] ? spin_lock
>>> /kernel/include/linux/spinlock.h:302
>>> [<ffffffff84a1c550>] ? snd_pcm_stream_lock+0x80/0xd0
>>> /kernel/sound/core/pcm_native.c:104
>>> [< inline >] kasan_report /kernel/mm/kasan/report.c:259
>>> [<ffffffff8170a0be>] __asan_report_load8_noabort+0x3e/0x40
>>> /kernel/mm/kasan/report.c:280
>>> [<ffffffff81792a0b>] ? kill_fasync+0x3fb/0x420
>>> /kernel/fs/fcntl.c:729
>>> [<ffffffff81792a0b>] kill_fasync+0x3fb/0x420 /kernel/fs/fcntl.c:729
>>> [<ffffffff84a36e08>] snd_pcm_period_elapsed+0x1c8/0x230
>>> /kernel/sound/core/pcm_lib.c:1890
>>> [<ffffffff84b6e2e0>] ? get_bound_vga.isra.21.part.22+0x140/0x140
>>> /kernel/sound/pci/hda/hda_intel.c:1327
>>> [<ffffffff84b0637d>] stream_update+0xad/0xe0
>>> /kernel/sound/pci/hda/hda_controller.c:923
>>> [<ffffffff84c1583e>] snd_hdac_bus_handle_stream_irq+0x24e/0x350
>>> /kernel/sound/hda/hdac_controller.c:449
>>> [<ffffffff84b062d0>] ? azx_init_chip+0x100/0x100
>>> /kernel/sound/pci/hda/hda_controller.c:890
>>> [<ffffffff84b04d24>] ? azx_interrupt+0x14/0x4d0
>>> /kernel/sound/pci/hda/hda_controller.c:929
>>> [<ffffffff84b04eee>] azx_interrupt+0x1de/0x4d0
>>> /kernel/sound/pci/hda/hda_controller.c:954
>>> [<ffffffff84b04d10>] ? azx_stop_chip+0x20/0x20
>>> /kernel/sound/pci/hda/hda_controller.c:908
>>> [<ffffffff8143d9e3>] handle_irq_event_percpu+0xf3/0x790
>>> /kernel/kernel/irq/handle.c:145
>>> [<ffffffff8143e127>] handle_irq_event+0xa7/0x140
>>> /kernel/kernel/irq/handle.c:192
>>> [<ffffffff81447f81>] handle_edge_irq+0x1e1/0x8d0
>>> /kernel/kernel/irq/chip.c:623
>>> [< inline >] generic_handle_irq_desc
>>> /kernel/include/linux/irqdesc.h:146
>>> [<ffffffff811ad739>] handle_irq+0x109/0x2a0
>>> /kernel/arch/x86/kernel/irq_64.c:78
>>> [< inline >] ? rcu_lock_release
>>> /kernel/include/linux/rcupdate.h:491
>>> [< inline >] ? rcu_read_unlock
>>> /kernel/include/linux/rcupdate.h:926
>>> [< inline >] ? __atomic_notifier_call_chain
>>> /kernel/kernel/notifier.c:184
>>> [<ffffffff81369c4f>] ? atomic_notifier_call_chain+0xbf/0x140
>>> /kernel/kernel/notifier.c:193
>>> [<ffffffff81369b90>] ? __atomic_notifier_call_chain+0x150/0x150
>>> /kernel/include/linux/rcupdate.h:922
>>> [<ffffffff811ac36d>] do_IRQ+0x7d/0x1a0
>>> /kernel/arch/x86/kernel/irq.c:240
>>> [<ffffffff85dac40c>] common_interrupt+0x8c/0x8c
>>> /kernel/arch/x86/entry/entry_64.S:454
>>> <EOI> [<ffffffff812245c6>] ? native_safe_halt+0x6/0x10
>>> /kernel/./arch/x86/include/asm/irqflags.h:49
>>> [<ffffffff81405ced>] ? trace_hardirqs_on+0xd/0x10
>>> /kernel/kernel/locking/lockdep.c:2635
>>> [< inline >] arch_safe_halt
>>> /kernel/./arch/x86/include/asm/paravirt.h:117
>>> [<ffffffff811bf152>] default_idle+0x22/0x2d0
>>> /kernel/arch/x86/kernel/process.c:307
>>> [<ffffffff811c053a>] arch_cpu_idle+0xa/0x10
>>> /kernel/arch/x86/kernel/process.c:298
>>> [<ffffffff813eb618>] default_idle_call+0x48/0x70
>>> /kernel/kernel/sched/idle.c:93
>>> [< inline >] cpuidle_idle_call
>>> /kernel/kernel/sched/idle.c:151
>>> [< inline >] cpu_idle_loop /kernel/kernel/sched/idle.c:242
>>> [<ffffffff813ebaa7>] cpu_startup_entry+0x467/0x600
>>> /kernel/kernel/sched/idle.c:291
>>> [<ffffffff81201432>] start_secondary+0x2b2/0x380
>>> /kernel/arch/x86/kernel/smpboot.c:259
>>> [<ffffffff81201180>] ? set_cpu_sibling_map+0x18a0/0x18a0
>>> /kernel/include/linux/topology.h:80
>>> Memory state around the buggy address:
>>> ffff880067691c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ffff880067691d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> >ffff880067691d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ^
>>> ffff880067691e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ffff880067691e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ==================================================================
>>>
>>> It seems that in function snd_pcm_detach_substream, when freeing
>>> runtime
>>> structure, it did not handle its fasync
>>> data pointer. Any ideas? Thanks.
>> Well, fasync doesn't need a cleanup usually. Do you have a proper
>> reproducer code?
> Sorry, I cannot reproduce it. I will apply your patch and test it. I
> will tell you the result whether it is okay a few days later.
> Thanks.
>
>> In anyway, try the patch below. I'm not sure whether this would help,
>> but if the path is via kill_fasync(), it'd be good to put in the
>> protected context.
>>
During the last few weeks, I have not seen the bug any more after
applying your patch. Thanks.
>>
>> Takashi
>>
>> ---
>> diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
>> index 3a9b66c6e09c..0aca39762ed0 100644
>> --- a/sound/core/pcm_lib.c
>> +++ b/sound/core/pcm_lib.c
>> @@ -1886,8 +1886,8 @@ void snd_pcm_period_elapsed(struct
>> snd_pcm_substream *substream)
>> snd_timer_interrupt(substream->timer, 1);
>> #endif
>> _end:
>> - snd_pcm_stream_unlock_irqrestore(substream, flags);
>> kill_fasync(&runtime->fasync, SIGIO, POLL_IN);
>> + snd_pcm_stream_unlock_irqrestore(substream, flags);
>> }
>> EXPORT_SYMBOL(snd_pcm_period_elapsed);
>
On Thu, 21 Apr 2016 04:13:13 +0200,
Baozeng Ding wrote:
>
>
>
> On 2016/4/6 19:37, Baozeng Ding wrote:
> >
> >
> > On 2016/4/5 22:18, Takashi Iwai wrote:
> >> On Tue, 05 Apr 2016 15:51:30 +0200,
> >> Baozeng Ding wrote:
> >>> Hi all,
> >>> I've got the following report (use-after-free in kill_fasync) while
> >>> running syzkaller.
> >>> Unfortunately no reproducer.The kernel version is 4.5 (on Mar 16 commit
> >>> 09fd671ccb2475436bd5f597f751ca4a7d177aea).
> >>>
> >>> ==================================================================
> >>> BUG: KASAN: use-after-free in kill_fasync+0x3fb/0x420 at addr
> >>> ffff880067691d88
> >>> Read of size 8 by task swapper/2/0
> >>> =============================================================================
> >>>
> >>> BUG kmalloc-2048 (Not tainted): kasan: bad access detected
> >>> -----------------------------------------------------------------------------
> >>>
> >>>
> >>> Disabling lock debugging due to kernel taint
> >>> INFO: Allocated in 0xbbbbbbbbbbbbbbbb age=18446678412249576073
> >>> cpu=2245704320 pid=-1
> >>> [< inline >] kmalloc /kernel/include/linux/slab.h:472
> >>> [< inline >] kzalloc /kernel/include/linux/slab.h:616
> >>> [< none >] snd_pcm_attach_substream+0x3b4/0xb10
> >>> /kernel/sound/core/pcm.c:966
> >>> [< none >] ___slab_alloc+0x4c7/0x500 /kernel/mm/slub.c:2446
> >>> [< none >] __slab_alloc+0x4c/0x90 /kernel/mm/slub.c:2475
> >>> [< inline >] slab_alloc_node /kernel/mm/slub.c:2538
> >>> [< inline >] slab_alloc /kernel/mm/slub.c:2580
> >>> [< none >] kmem_cache_alloc_trace+0x262/0x300
> >>> /kernel/mm/slub.c:2597
> >>> [< inline >] kmalloc /kernel/include/linux/slab.h:472
> >>> [< inline >] kzalloc /kernel/include/linux/slab.h:616
> >>> [< none >] snd_pcm_attach_substream+0x3b4/0xb10
> >>> /kernel/sound/core/pcm.c:966
> >>> [< none >] snd_pcm_open_substream+0x84/0x450
> >>> /kernel/sound/core/pcm_native.c:2262
> >>> [< inline >] snd_pcm_oss_open_file
> >>> /kernel/sound/core/oss/pcm_oss.c:2346
> >>> [< none >] snd_pcm_oss_open.part.17+0x5a4/0x1100
> >>> /kernel/sound/core/oss/pcm_oss.c:2428
> >>> [< none >] snd_pcm_oss_open+0x35/0x50
> >>> /kernel/sound/core/oss/pcm_oss.c:2392
> >>> [< none >] soundcore_open+0x30f/0x640
> >>> /kernel/sound/sound_core.c:639
> >>> [< none >] chrdev_open+0x22a/0x4c0 /kernel/fs/char_dev.c:388
> >>> [< none >] do_dentry_open+0x6a2/0xcb0 /kernel/fs/open.c:736
> >>> [< none >] vfs_open+0x17b/0x1f0 /kernel/fs/open.c:853
> >>> [< inline >] do_last /kernel/fs/namei.c:3258
> >>> [< none >] path_openat+0x4837/0x5830 /kernel/fs/namei.c:3394
> >>> [< none >] do_filp_open+0x18e/0x250 /kernel/fs/namei.c:3429
> >>> [< none >] do_sys_open+0x201/0x420 /kernel/fs/open.c:1022
> >>> [< inline >] SYSC_open /kernel/fs/open.c:1040
> >>> [< none >] SyS_open+0x2d/0x40 /kernel/fs/open.c:1035
> >>> INFO: Freed in 0x10000b076 age=18446678416544543380 cpu=0 pid=0
> >>> [< none >] snd_pcm_detach_substream+0x134/0x280
> >>> /kernel/sound/core/pcm.c:1017
> >>> [< none >] __slab_free+0x1e8/0x300 /kernel/mm/slub.c:2657
> >>> [< inline >] slab_free /kernel/mm/slub.c:2810
> >>> [< none >] kfree+0x24e/0x2d0 /kernel/mm/slub.c:3661
> >>> [< none >] snd_pcm_detach_substream+0x134/0x280
> >>> /kernel/sound/core/pcm.c:1017
> >>> [< none >] snd_pcm_release_substream.part.38+0x219/0x2f0
> >>> /kernel/sound/core/pcm_native.c:2250
> >>> [< none >] snd_pcm_release_substream+0x59/0x70
> >>> /kernel/sound/core/pcm_native.c:2251
> >>> [< none >] snd_pcm_oss_release_file+0x45/0xb0
> >>> /kernel/sound/core/oss/pcm_oss.c:2305
> >>> [< none >] snd_pcm_oss_release+0xfa/0x250
> >>> /kernel/sound/core/oss/pcm_oss.c:2485
> >>> [< none >] __fput+0x236/0x780 /kernel/fs/file_table.c:208
> >>> [< none >] ____fput+0x15/0x20 /kernel/fs/file_table.c:244
> >>> [< none >] task_work_run+0x16b/0x200
> >>> /kernel/kernel/task_work.c:115
> >>> [< inline >] exit_task_work
> >>> /kernel/include/linux/task_work.h:21
> >>> [< none >] do_exit+0x87f/0x2c90 /kernel/kernel/exit.c:748
> >>> [< none >] do_group_exit+0x108/0x330
> >>> /kernel/kernel/exit.c:878
> >>> [< inline >] SYSC_exit_group /kernel/kernel/exit.c:889
> >>> [< none >] SyS_exit_group+0x1d/0x20 /kernel/kernel/exit.c:887
> >>> [< none >] entry_SYSCALL_64_fastpath+0x23/0xc1
> >>> /kernel/arch/x86/entry/entry_64.S:207
> >>> INFO: Slab 0xffffea00019da400 objects=13 used=8 fp=0xffff880067691be0
> >>> flags=0x5fffc0000004080
> >>> INFO: Object 0xffff880067691bd8 @offset=7128 fp=0xbbbbbbbbbbbbbbbb
> >>> Call Trace:
> >>> <IRQ> [< inline >] __dump_stack /kernel/lib/dump_stack.c:15
> >>> <IRQ> [<ffffffff82945051>] dump_stack+0xb3/0x112
> >>> /kernel/lib/dump_stack.c:51
> >>> [<ffffffff817009ad>] print_trailer+0x10d/0x190 /kernel/mm/slub.c:668
> >>> [<ffffffff817074af>] object_err+0x2f/0x40 /kernel/mm/slub.c:675
> >>> [< inline >] print_address_description
> >>> /kernel/mm/kasan/report.c:138
> >>> [<ffffffff81709ca5>] kasan_report_error+0x215/0x530
> >>> /kernel/mm/kasan/report.c:236
> >>> [< inline >] ? spin_lock
> >>> /kernel/include/linux/spinlock.h:302
> >>> [<ffffffff84a1c550>] ? snd_pcm_stream_lock+0x80/0xd0
> >>> /kernel/sound/core/pcm_native.c:104
> >>> [< inline >] kasan_report /kernel/mm/kasan/report.c:259
> >>> [<ffffffff8170a0be>] __asan_report_load8_noabort+0x3e/0x40
> >>> /kernel/mm/kasan/report.c:280
> >>> [<ffffffff81792a0b>] ? kill_fasync+0x3fb/0x420
> >>> /kernel/fs/fcntl.c:729
> >>> [<ffffffff81792a0b>] kill_fasync+0x3fb/0x420 /kernel/fs/fcntl.c:729
> >>> [<ffffffff84a36e08>] snd_pcm_period_elapsed+0x1c8/0x230
> >>> /kernel/sound/core/pcm_lib.c:1890
> >>> [<ffffffff84b6e2e0>] ? get_bound_vga.isra.21.part.22+0x140/0x140
> >>> /kernel/sound/pci/hda/hda_intel.c:1327
> >>> [<ffffffff84b0637d>] stream_update+0xad/0xe0
> >>> /kernel/sound/pci/hda/hda_controller.c:923
> >>> [<ffffffff84c1583e>] snd_hdac_bus_handle_stream_irq+0x24e/0x350
> >>> /kernel/sound/hda/hdac_controller.c:449
> >>> [<ffffffff84b062d0>] ? azx_init_chip+0x100/0x100
> >>> /kernel/sound/pci/hda/hda_controller.c:890
> >>> [<ffffffff84b04d24>] ? azx_interrupt+0x14/0x4d0
> >>> /kernel/sound/pci/hda/hda_controller.c:929
> >>> [<ffffffff84b04eee>] azx_interrupt+0x1de/0x4d0
> >>> /kernel/sound/pci/hda/hda_controller.c:954
> >>> [<ffffffff84b04d10>] ? azx_stop_chip+0x20/0x20
> >>> /kernel/sound/pci/hda/hda_controller.c:908
> >>> [<ffffffff8143d9e3>] handle_irq_event_percpu+0xf3/0x790
> >>> /kernel/kernel/irq/handle.c:145
> >>> [<ffffffff8143e127>] handle_irq_event+0xa7/0x140
> >>> /kernel/kernel/irq/handle.c:192
> >>> [<ffffffff81447f81>] handle_edge_irq+0x1e1/0x8d0
> >>> /kernel/kernel/irq/chip.c:623
> >>> [< inline >] generic_handle_irq_desc
> >>> /kernel/include/linux/irqdesc.h:146
> >>> [<ffffffff811ad739>] handle_irq+0x109/0x2a0
> >>> /kernel/arch/x86/kernel/irq_64.c:78
> >>> [< inline >] ? rcu_lock_release
> >>> /kernel/include/linux/rcupdate.h:491
> >>> [< inline >] ? rcu_read_unlock
> >>> /kernel/include/linux/rcupdate.h:926
> >>> [< inline >] ? __atomic_notifier_call_chain
> >>> /kernel/kernel/notifier.c:184
> >>> [<ffffffff81369c4f>] ? atomic_notifier_call_chain+0xbf/0x140
> >>> /kernel/kernel/notifier.c:193
> >>> [<ffffffff81369b90>] ? __atomic_notifier_call_chain+0x150/0x150
> >>> /kernel/include/linux/rcupdate.h:922
> >>> [<ffffffff811ac36d>] do_IRQ+0x7d/0x1a0
> >>> /kernel/arch/x86/kernel/irq.c:240
> >>> [<ffffffff85dac40c>] common_interrupt+0x8c/0x8c
> >>> /kernel/arch/x86/entry/entry_64.S:454
> >>> <EOI> [<ffffffff812245c6>] ? native_safe_halt+0x6/0x10
> >>> /kernel/./arch/x86/include/asm/irqflags.h:49
> >>> [<ffffffff81405ced>] ? trace_hardirqs_on+0xd/0x10
> >>> /kernel/kernel/locking/lockdep.c:2635
> >>> [< inline >] arch_safe_halt
> >>> /kernel/./arch/x86/include/asm/paravirt.h:117
> >>> [<ffffffff811bf152>] default_idle+0x22/0x2d0
> >>> /kernel/arch/x86/kernel/process.c:307
> >>> [<ffffffff811c053a>] arch_cpu_idle+0xa/0x10
> >>> /kernel/arch/x86/kernel/process.c:298
> >>> [<ffffffff813eb618>] default_idle_call+0x48/0x70
> >>> /kernel/kernel/sched/idle.c:93
> >>> [< inline >] cpuidle_idle_call
> >>> /kernel/kernel/sched/idle.c:151
> >>> [< inline >] cpu_idle_loop /kernel/kernel/sched/idle.c:242
> >>> [<ffffffff813ebaa7>] cpu_startup_entry+0x467/0x600
> >>> /kernel/kernel/sched/idle.c:291
> >>> [<ffffffff81201432>] start_secondary+0x2b2/0x380
> >>> /kernel/arch/x86/kernel/smpboot.c:259
> >>> [<ffffffff81201180>] ? set_cpu_sibling_map+0x18a0/0x18a0
> >>> /kernel/include/linux/topology.h:80
> >>> Memory state around the buggy address:
> >>> ffff880067691c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >>> ffff880067691d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >>> >ffff880067691d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >>> ^
> >>> ffff880067691e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >>> ffff880067691e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >>> ==================================================================
> >>>
> >>> It seems that in function snd_pcm_detach_substream, when freeing
> >>> runtime
> >>> structure, it did not handle its fasync
> >>> data pointer. Any ideas? Thanks.
> >> Well, fasync doesn't need a cleanup usually. Do you have a proper
> >> reproducer code?
> > Sorry, I cannot reproduce it. I will apply your patch and test it. I
> > will tell you the result whether it is okay a few days later.
> > Thanks.
> >
> >> In anyway, try the patch below. I'm not sure whether this would help,
> >> but if the path is via kill_fasync(), it'd be good to put in the
> >> protected context.
> >>
> During the last few weeks, I have not seen the bug any more after
> applying your patch. Thanks.
Thanks, good to hear!
The patch has been queued in for-next branch, so it'll be merged in
4.7.
Takashi