ALSA: usb-audio: Add spinlock to stop_urbs()

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>

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 1f757a7..c320226 100644 (file)
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -927,6 +927,7 @@ void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
 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_endpoint *ep, bool force)
        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)) {