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

[Heiko Carstens <hca@linux.ibm.com>]

On Wed, Oct 28, 2026 at 12:48:25PM +0800, Jiale Yao wrote:
> 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);

I changed this to use a static DECLARE_RWSEM() declaration; and also
removed the incorrect Fixes tag - this is probably broken since the
driver exists.

Applied, thanks!