On Thu, Dec 12, 2019 at 10:09 PM Marek Szyprowski
<m.szyprowski@xxxxxxxxxxx> wrote:
> -> #1 (&card->controls_rwsem){++++}:
> snd_ctl_add_replace+0x3c/0x84
> dapm_create_or_share_kcontrol+0x24c/0x2e0
> snd_soc_dapm_new_widgets+0x308/0x594
> snd_soc_bind_card+0x80c/0xac8
> devm_snd_soc_register_card+0x34/0x6c
> asoc_simple_probe+0x244/0x4a0
> platform_drv_probe+0x6c/0xa4
> really_probe+0x200/0x490
> driver_probe_device+0x78/0x1f8
> bus_for_each_drv+0x74/0xb8
> __device_attach+0xd4/0x16c
> bus_probe_device+0x88/0x90
> deferred_probe_work_func+0x3c/0xd0
> process_one_work+0x22c/0x7c4
> worker_thread+0x44/0x524
> kthread+0x130/0x164
> ret_from_fork+0x14/0x20
> 0x0
A key observation here is: the card registration got deferred.
>
> -> #0 (&card->dapm_mutex){+.+.}:
> lock_acquire+0xe8/0x270
> __mutex_lock+0x9c/0xb18
> mutex_lock_nested+0x1c/0x24
> max98090_shdn_save+0x1c/0x28
> max98090_put_enum_double+0x20/0x40
> snd_ctl_ioctl+0x190/0xbb8
> do_vfs_ioctl+0xb0/0xab0
> ksys_ioctl+0x34/0x5c
> ret_fast_syscall+0x0/0x28
> 0xbe9094dc
And this is an ioctl( ) on a control (e.g. controlC0).
I have no enough resources to test and trace the code temporarily.
But is it possible:
- snd_card_new( ) succeed in snd_soc_bind_card( ), so that userspace
can see the control
- code in later snd_soc_bind_card( ) decided to defer the probe
- soc_cleanup_card_resources( ) may forget to clean the control? (not
sure about this)
Then, when the card is instantiating next time, some userspace program
tries to ioctl( ) to get the deadlock possibility and the NULL
dereference.
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