linux-kernel - Re: [syzbot] [sound?] possible deadlock in snd_pcm_period

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Date: Sat, 16 Mar 2024 09:23:02 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+28c1a5a5b041a754b947@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [sound?] possible deadlock in snd_pcm_period_elapsed (4)

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  master

--- x/sound/core/timer.c
+++ y/sound/core/timer.c
@@ -409,8 +409,9 @@ static void snd_timer_close_locked(struc
 	struct snd_timer *timer = timeri->timer;
 
 	if (timer) {
-		guard(spinlock)(&timer->lock);
+		spin_lock_irq(&timer->lock);
 		timeri->flags |= SNDRV_TIMER_IFLG_DEAD;
+		spin_unlock_irq(&timer->lock);
 	}
 
 	if (!list_empty(&timeri->open_list)) {
--- x/drivers/virtio/virtio_ring.c
+++ y/drivers/virtio/virtio_ring.c
@@ -316,7 +316,13 @@ static void *vring_alloc_queue(struct vi
 		return dma_alloc_coherent(dma_dev, size,
 					  dma_handle, flag);
 	} else {
-		void *queue = alloc_pages_exact(PAGE_ALIGN(size), flag);
+		void *queue;
+		unsigned long sz = PAGE_ALIGN(size);
+		unsigned int order = 0;
+
+		while ((PAGE_SIZE << order) < sz)
+			order++;
+		queue = (void *) __get_free_pages(flag, order);
 
 		if (queue) {
 			phys_addr_t phys_addr = virt_to_phys(queue);
@@ -334,7 +340,7 @@ static void *vring_alloc_queue(struct vi
 			 * unrepresentable address.
 			 */
 			if (WARN_ON_ONCE(*dma_handle != phys_addr)) {
-				free_pages_exact(queue, PAGE_ALIGN(size));
+				free_pages((unsigned long) queue, order);
 				return NULL;
 			}
 		}
@@ -348,8 +354,14 @@ static void vring_free_queue(struct virt
 {
 	if (vring_use_dma_api(vdev))
 		dma_free_coherent(dma_dev, size, queue, dma_handle);
-	else
-		free_pages_exact(queue, PAGE_ALIGN(size));
+	else {
+		unsigned long sz = PAGE_ALIGN(size);
+		unsigned int order = 0;
+
+		while ((PAGE_SIZE << order) < sz)
+			order++;
+		free_pages((unsigned long) queue, order);
+	}
 }
 
 /*
--