[PATCH 5.15 006/207] ALSA: usb-audio: Add spinlock to stop_urbs()

Greg Kroah-Hartman
2021-12-06T15:49:53Z

From: Takashi Iwai <tiwai@suse.de>

commit 0ef74366bc150dda4f53c546dfa6e8f7c707e087 upstream.

In theory, stop_urbs() may be called concurrently.
Although we have the state check beforehand, it's safer to apply
ep->lock during the critical list head manipulations.

Link: https://lore.kernel.org/r/20210929080844.11583-8-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/usb/endpoint.c | 3 +++
1 file changed, 3 insertions(+)

--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -927,6 +927,7 @@ void snd_usb_endpoint_sync_pending_stop(
static int stop_urbs(struct snd_usb_endpoint *ep, bool force)
{
unsigned int i;
+ unsigned long flags;

if (!force && atomic_read(&ep->running))
return -EBUSY;
@@ -934,9 +935,11 @@ static int stop_urbs(struct snd_usb_endp
if (!ep_state_update(ep, EP_STATE_RUNNING, EP_STATE_STOPPING))
return 0;

+ spin_lock_irqsave(&ep->lock, flags);
INIT_LIST_HEAD(&ep->ready_playback_urbs);
ep->next_packet_head = 0;
ep->next_packet_queued = 0;
+ spin_unlock_irqrestore(&ep->lock, flags);

for (i = 0; i < ep->nurbs; i++) {
if (test_bit(i, &ep->active_mask)) {