ALSA: fireworks: accessing to user space outside spinlock

In hwdep interface of fireworks driver, accessing to user space is in a
critical section with disabled local interrupt. Depending on architecture,
accessing to user space can cause page fault exception. Then local
processor stores machine status and handles the synchronous event. A
handler corresponding to the event can call task scheduler to wait for
preparing pages. In a case of usage of single core processor, the state to
disable local interrupt is worse because it don't handle usual interrupts
from hardware.

This commit fixes this bug, performing the accessing outside spinlock. This
commit also gives up counting the number of queued response messages to
simplify ring-buffer management.

Reported-by: Vaishali Thakkar <vaishali.thakkar@oracle.com>
Cc: stable@vger.kernel.org
Fixes: 555e8a8f7f14('ALSA: fireworks: Add command/response functionality into hwdep interface')
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 2 insertions, 3 deletions

diff --git a/sound/firewire/fireworks/fireworks_transaction.c b/sound/firewire/fireworks/fireworks_transaction.c
index f550808..36a08ba 100644
--- a/sound/firewire/fireworks/fireworks_transaction.c
+++ b/sound/firewire/fireworks/fireworks_transaction.c
@@ -121,11 +121,11 @@ copy_resp_to_buf(struct snd_efw *efw, void *data, size_t length, int *rcode)
 	size_t capacity, till_end;
 	struct snd_efw_transaction *t;
 
-	spin_lock_irq(&efw->lock);
-
 	t = (struct snd_efw_transaction *)data;
 	length = min_t(size_t, be32_to_cpu(t->length) * sizeof(u32), length);
 
+	spin_lock_irq(&efw->lock);
+
 	if (efw->push_ptr < efw->pull_ptr)
 		capacity = (unsigned int)(efw->pull_ptr - efw->push_ptr);
 	else
@@ -155,7 +155,6 @@ copy_resp_to_buf(struct snd_efw *efw, void *data, size_t length, int *rcode)
 	}
 
 	/* for hwdep */
-	efw->resp_queues++;
 	wake_up(&efw->hwdep_wait);
 
 	*rcode = RCODE_COMPLETE;