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ALSA: usb-audio: Fix racy list management in output queue

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[ Upstream commit 5b6cc38f3f3f37109ce72b60bda215a5f6892c0b ]

The linked list entry from FIFO is peeked at
queue_pending_output_urbs() but the actual element pop-out is
performed outside the spinlock, and it's potentially racy.

Do delete the link at the right place inside the spinlock.

Fixes: 8fdff6a319 ("ALSA: snd-usb: implement new endpoint streaming model")
Link: https://lore.kernel.org/r/20200424074016.14301-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Takashi Iwai
2020-04-24 09:40:16 +02:00
committed by Greg Kroah-Hartman
parent 2d50acd7db
commit d3a9803bc7
1 changed files with 3 additions and 3 deletions
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6
sound/usb/endpoint.c
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@@ -359,17 +359,17 @@ static void queue_pending_output_urbs(struct snd_usb_endpoint *ep)
ep->next_packet_read_pos %= MAX_URBS; ep->next_packet_read_pos %= MAX_URBS;
/* take URB out of FIFO */ /* take URB out of FIFO */
if (!list_empty(&ep->ready_playback_urbs)) if (!list_empty(&ep->ready_playback_urbs)) {
ctx = list_first_entry(&ep->ready_playback_urbs, ctx = list_first_entry(&ep->ready_playback_urbs,
struct snd_urb_ctx, ready_list); struct snd_urb_ctx, ready_list);
list_del_init(&ctx->ready_list);
}
} }
spin_unlock_irqrestore(&ep->lock, flags); spin_unlock_irqrestore(&ep->lock, flags);
if (ctx == NULL) if (ctx == NULL)
return; return;
list_del_init(&ctx->ready_list);
/* copy over the length information */ /* copy over the length information */
for (i = 0; i < packet->packets; i++) for (i = 0; i < packet->packets; i++)
ctx->packet_size[i] = packet->packet_size[i]; ctx->packet_size[i] = packet->packet_size[i];