ALSA: fireface: fix locking bug in ff400_copy_msg_to_user()

The ff400_copy_msg_to_user() function drops the spin lock to call
copy_to_user().  However, if the copy_to_user() fails, then it must
take the lock again before returning.  Failure to take the lock leads
to a double unlock in the caller, hwdep_read().

Fixes: acdebd8b4c0c ("ALSA: fireface: implement message parser for Fireface 400")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/Y8at+W/7OGvEBY8O@kili
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/firewire/fireface/ff-protocol-former.c b/sound/firewire/fireface/ff-protocol-former.c
index f58008762fe661145e89ec0814e0699db4ee6894..fa41de978756035fe29ac8c43d82b8724a3ef92a 100644 (file)
--- a/sound/firewire/fireface/ff-protocol-former.c
+++ b/sound/firewire/fireface/ff-protocol-former.c
@@ -680,28 +680,30 @@ static long ff400_copy_msg_to_user(struct snd_ff *ff, char __user *buf, long cou
        struct ff400_msg_parser *parser = ff->msg_parser;
        u32 type = SNDRV_FIREWIRE_EVENT_FF400_MESSAGE;
        long consumed = 0;
+       int ret = 0;
 
        if (count < 8)
                return 0;
 
        spin_unlock_irq(&ff->lock);
-
        if (copy_to_user(buf, &type, sizeof(type)))
-               return -EFAULT;
-
+               ret = -EFAULT;
        spin_lock_irq(&ff->lock);
+       if (ret)
+               return ret;
 
        count -= sizeof(type);
        consumed += sizeof(type);
 
        while (count >= sizeof(*parser->msgs) && parser->pull_pos != parser->push_pos) {
                spin_unlock_irq(&ff->lock);
-
                if (copy_to_user(buf + consumed, parser->msgs + parser->pull_pos,
                                 sizeof(*parser->msgs)))
-                       return -EFAULT;
-
+                       ret = -EFAULT;
                spin_lock_irq(&ff->lock);
+               if (ret)
+                       return ret;
+
                ++parser->pull_pos;
                if (parser->pull_pos >= FF400_QUEUE_SIZE)
                        parser->pull_pos = 0;