[PATCH 0/6] Initialize device state before userspace registration

[PATCH 0/6] Initialize device state before userspace registration

[Jiale Yao]

Several drivers register character devices or sysfs attributes before
initializing synchronization objects and related state used by their
userspace entry points. Registration makes those entry points immediately
available, so a concurrent access can reach partially initialized state.

Move each initialization ahead of the corresponding registration. The
patches are independent and cover AoE, fsl-mc, MSHV, IBM VMC, DCSSBLK,
and the RDC321x watchdog.

Jiale Yao (6):
  aoe: initialize error message synchronization before registration
  bus: fsl-mc: initialize UAPI state before device registration
  Drivers: hv: initialize partition table before device registration
  misc: ibmvmc: initialize HMC state before device registration
  s390/dcssblk: initialize device semaphore before sysfs registration
  watchdog: rdc321x: initialize device state before registration

 drivers/block/aoe/aoechr.c       |  6 +++---
 drivers/bus/fsl-mc/fsl-mc-uapi.c |  6 ++----
 drivers/hv/mshv_root_main.c      |  6 +++---
 drivers/misc/ibmvmc.c            | 16 ++++++++--------
 drivers/s390/block/dcssblk.c     |  3 ++-
 drivers/watchdog/rdc321x_wdt.c   | 12 ++++++------
 6 files changed, 24 insertions(+), 25 deletions(-)

-- 
2.34.1

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

[Jiale Yao]

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

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

[sashiko-bot]

> 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>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261028044828.96177-2-yaojiale02@163.com?part=5

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

[Heiko Carstens]

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!