From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Zizhi Wo <wozizhi@huawei.com>,
	Nilay Shroff <nilay@linux.ibm.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Jens Axboe <axboe@kernel.dk>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.12 1153/1376] null_blk: free zones array on device power-off
Date: Sat, 12 Sep 2026 08:59:39 +0200
Message-ID: <20260912065633.252466699@linuxfoundation.org>
In-Reply-To: <20260912065607.535295758@linuxfoundation.org>
References: <20260912065607.535295758@linuxfoundation.org>
User-Agent: quilt/0.69
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zizhi Wo <wozizhi@huawei.com>

[ Upstream commit 2a6357a9b935a34f5508618fee8a7fffbf7722a8 ]

null_init_zoned_dev() allocates dev->zones when a zoned device is powered
on, but null_del_dev() never frees it on power-off; dev->zones is only
freed later in null_free_dev(), when the configfs directory is removed. If
the device is powered off and then on again, null_init_zoned_dev()
allocates a new array and overwrites the dev->zones pointer, leaking the
previous allocation each power cycle.

Free dev->zones in null_del_dev() via null_free_zoned_dev() to solve it.
And calling null_free_zoned_dev() in null_free_dev() is no longer necessary
because every caller already invokes null_del_dev() first: via
nullb_group_drop_item() before nullb_device_release(), in the
null_add_dev() error path of null_create_dev(), and in null_destroy_dev().
Remove the redundant call.

And take &lock around zone_cond_store() in the two store wrappers to
serialize dev->zones check-and-deref against its alloc/free, which already
run under &lock. The reason there was no problem before is that only
nullb_device_release() or null_exit() frees the dev->zones, which
guarantees that subsequent users won't access the configfs interface.

Fixes: ca4b2a011948 ("null_blk: add zone support")
Assisted-by: Claude-Code:GLM-5.2
Signed-off-by: Zizhi Wo <wozizhi@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://patch.msgid.link/20260725022509.714271-6-wozizhi@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/block/null_blk/main.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index bde38a4696fef..cf8b3283c48e8 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -572,8 +572,13 @@ static ssize_t nullb_device_zone_readonly_store(struct config_item *item,
 						const char *page, size_t count)
 {
 	struct nullb_device *dev = to_nullb_device(item);
+	ssize_t ret;
+
+	mutex_lock(&lock);
+	ret = zone_cond_store(dev, page, count, BLK_ZONE_COND_READONLY);
+	mutex_unlock(&lock);
 
-	return zone_cond_store(dev, page, count, BLK_ZONE_COND_READONLY);
+	return ret;
 }
 CONFIGFS_ATTR_WO(nullb_device_, zone_readonly);
 
@@ -581,8 +586,13 @@ static ssize_t nullb_device_zone_offline_store(struct config_item *item,
 					       const char *page, size_t count)
 {
 	struct nullb_device *dev = to_nullb_device(item);
+	ssize_t ret;
 
-	return zone_cond_store(dev, page, count, BLK_ZONE_COND_OFFLINE);
+	mutex_lock(&lock);
+	ret = zone_cond_store(dev, page, count, BLK_ZONE_COND_OFFLINE);
+	mutex_unlock(&lock);
+
+	return ret;
 }
 CONFIGFS_ATTR_WO(nullb_device_, zone_offline);
 
@@ -812,7 +822,6 @@ static void null_free_dev(struct nullb_device *dev)
 	if (!dev)
 		return;
 
-	null_free_zoned_dev(dev);
 	badblocks_exit(&dev->badblocks);
 	kfree(dev);
 }
@@ -1721,6 +1730,7 @@ static void null_del_dev(struct nullb *nullb)
 	}
 
 	put_disk(nullb->disk);
+	null_free_zoned_dev(dev);
 	if (nullb->tag_set == &nullb->__tag_set)
 		blk_mq_free_tag_set(nullb->tag_set);
 	kfree(nullb->queues);
-- 
2.53.0