ALSA: rawmidi: Fix kvfree() call in spinlock

At the conversion of locking with guard(), I overlooked that kvfree()
must not be called inside the spinlock unlike kfree(), and this was
caught by syzkaller now.

This patch reverts the conversion partially for restoring the kvfree()
call outside the spinlock.  It's not trivial to use guard() in this
context, unfortunately.

Fixes: 84bb065 ("ALSA: rawmidi: Use guard() for locking")
Reported-by: syzbot+351f8764833934c68836@syzkaller.appspotmail.com
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Closes: https://lore.kernel.org/6744737b.050a0220.1cc393.007e.GAE@google.com
Cc: <stable@vger.kernel.org>
Link: https://patch.msgid.link/20241125142041.16578-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: tiwai

sound/core/rawmidi.c

@@ -724,15 +724,17 @@ static int resize_runtime_buffer(struct snd_rawmidi_substream *substream,
 		newbuf = kvzalloc(params->buffer_size, GFP_KERNEL);
 		if (!newbuf)
 			return -ENOMEM;
-		guard(spinlock_irq)(&substream->lock);
+		spin_lock_irq(&substream->lock);
 		if (runtime->buffer_ref) {
+			spin_unlock_irq(&substream->lock);
 			kvfree(newbuf);
 			return -EBUSY;
 		}
 		oldbuf = runtime->buffer;
 		runtime->buffer = newbuf;
 		runtime->buffer_size = params->buffer_size;
 		__reset_runtime_ptrs(runtime, is_input);
+		spin_unlock_irq(&substream->lock);
 		kvfree(oldbuf);
 	}
 	runtime->avail_min = params->avail_min;