From 5c06d68bc2a174a6b82dce9f100f55173b9a5189 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 12 Jan 2016 14:03:33 +0100 Subject: [PATCH] ALSA: usb-audio: Avoid calling usb_autopm_put_interface() at disconnect 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: [] usb_autopm_put_interface+0xf/0x30 PGD 0 Call Trace: [] snd_usb_autosuspend+0x14/0x20 [] snd_usb_pcm_close.isra.14+0x5c/0x90 [] snd_usb_playback_close+0xf/0x20 [] snd_pcm_release_substream.part.36+0x3a/0x90 [] snd_pcm_release+0xa3/0xb0 [] snd_disconnect_release+0xd0/0xe0 [] __fput+0x97/0x1d0 [] ____fput+0x9/0x10 [] task_work_run+0x72/0x90 [] do_exit+0x280/0xa80 [] do_group_exit+0x3a/0xa0 [] get_signal+0x1df/0x540 [] do_signal+0x23/0x620 [] ? do_readv_writev+0x128/0x200 [] prepare_exit_to_usermode+0x91/0xd0 [] syscall_return_slowpath+0x9a/0x120 [] ? __sys_recvmsg+0x5d/0x70 [] ? ktime_get_ts64+0x45/0xe0 [] ? SyS_poll+0x60/0xf0 [] 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: Signed-off-by: Takashi Iwai --- 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); }