[PATCH V5 5/9] null_blk: free zones array on device power-off

[Zizhi Wo <wozizhi@huaweicloud.com>]

From: Zizhi Wo <wozizhi@huawei.com>

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>
---
 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 df85189f0b69..e063c931dfca 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -579,8 +579,13 @@ 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);
 
@@ -588,8 +593,13 @@ 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);
 
@@ -836,7 +846,6 @@ static void null_free_dev(struct nullb_device *dev)
 	if (!dev)
 		return;
 
-	null_free_zoned_dev(dev);
 	badblocks_exit(&dev->badblocks);
 	kfree(dev);
 }
@@ -1777,6 +1786,7 @@ 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);
-- 
2.52.0