[PATCH 5/6] s390/dcssblk: initialize device semaphore before sysfs registration

[Jiale Yao <yaojiale02@163.com>]

device_create_file() makes the add and remove attributes writable before
the device list semaphore is initialized. A sysfs write racing module
initialization can therefore acquire an uninitialized rwsem.

Initialize the semaphore before registering the root device and its
attributes.

Fixes: c369527f18f8 ("[S390] pm: dcssblk power management callbacks.")
Cc: stable@vger.kernel.org
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 drivers/s390/block/dcssblk.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index e5a02c2990d0..46dd7eb9ca7d 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -1013,6 +1013,8 @@ dcssblk_init(void)
 {
 	int rc;
 
+	init_rwsem(&dcssblk_devices_sem);
+
 	dcssblk_root_dev = root_device_register("dcssblk");
 	if (IS_ERR(dcssblk_root_dev))
 		return PTR_ERR(dcssblk_root_dev);
@@ -1026,7 +1028,6 @@ dcssblk_init(void)
 	if (rc < 0)
 		goto out_root;
 	dcssblk_major = rc;
-	init_rwsem(&dcssblk_devices_sem);
 
 	dcssblk_check_params();
 	return 0;
-- 
2.34.1