ALSA PCM may still have a leftover instance after disconnection and it delays its release. The problem is that the PCM close code path of USB-audio driver has a call of snd_usb_autosuspend(). This involves with the call of usb_autopm_put_interface() and it may lead to a kernel Oops due to the NULL object like:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000190 IP: [<ffffffff815ae7ef>] usb_autopm_put_interface+0xf/0x30 PGD 0 Call Trace: [<ffffffff8173bd94>] snd_usb_autosuspend+0x14/0x20 [<ffffffff817461bc>] snd_usb_pcm_close.isra.14+0x5c/0x90 [<ffffffff8174621f>] snd_usb_playback_close+0xf/0x20 [<ffffffff816ef58a>] snd_pcm_release_substream.part.36+0x3a/0x90 [<ffffffff816ef6b3>] snd_pcm_release+0xa3/0xb0 [<ffffffff816debb0>] snd_disconnect_release+0xd0/0xe0 [<ffffffff8114d417>] __fput+0x97/0x1d0 [<ffffffff8114d589>] ____fput+0x9/0x10 [<ffffffff8109e452>] task_work_run+0x72/0x90 [<ffffffff81088510>] do_exit+0x280/0xa80 [<ffffffff8108996a>] do_group_exit+0x3a/0xa0 [<ffffffff8109261f>] get_signal+0x1df/0x540 [<ffffffff81040903>] do_signal+0x23/0x620 [<ffffffff8114c128>] ? do_readv_writev+0x128/0x200 [<ffffffff810012e1>] prepare_exit_to_usermode+0x91/0xd0 [<ffffffff810013ba>] syscall_return_slowpath+0x9a/0x120 [<ffffffff817587cd>] ? __sys_recvmsg+0x5d/0x70 [<ffffffff810d2765>] ? ktime_get_ts64+0x45/0xe0 [<ffffffff8115dea0>] ? SyS_poll+0x60/0xf0 [<ffffffff818d2327>] int_ret_from_sys_call+0x25/0x8f

We have already a check of disconnection in snd_usb_autoresume(), but the check is missing its counterpart. The fix is just to put the same check in snd_usb_autosuspend(), too.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=109431 Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/usb/card.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/sound/usb/card.c b/sound/usb/card.c index 18f56646ce86..1f09d9591276 100644 --- a/sound/usb/card.c +++ b/sound/usb/card.c @@ -675,6 +675,8 @@ int snd_usb_autoresume(struct snd_usb_audio *chip)

void snd_usb_autosuspend(struct snd_usb_audio *chip) { + if (atomic_read(&chip->shutdown)) + return; if (atomic_dec_and_test(&chip->active)) usb_autopm_put_interface(chip->pm_intf); }