[PATCH 0/1] s390/dasd: fix locking error

[PATCH 0/1] s390/dasd: fix locking error

[Stefan Haberland]

Hi Jens,

please apply the following patch that fixes a locking error in the DASD
driver. Thanks.

Jan Höppner (1):
  s390/dasd: Use correct lock while counting channel queue length

 drivers/s390/block/dasd_ioctl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.39.2

[PATCH 1/1] s390/dasd: Use correct lock while counting channel queue length

[Stefan Haberland]

From: Jan Höppner <hoeppner@linux.ibm.com>

The lock around counting the channel queue length in the BIODASDINFO
ioctl was incorrectly changed to the dasd_block->queue_lock with commit
583d6535cb9d ("dasd: remove dead code"). This can lead to endless list
iterations and a subsequent crash.

The queue_lock is supposed to be used only for queue lists belonging to
dasd_block. For dasd_device related queue lists the ccwdev lock must be
used.

Fix the mentioned issues by correctly using the ccwdev lock instead of
the queue lock.

Fixes: 583d6535cb9d ("dasd: remove dead code")
Cc: stable@vger.kernel.org # v5.0+
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
---
 drivers/s390/block/dasd_ioctl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c
index 9327dcdd6e5e..8fca725b3dae 100644
--- a/drivers/s390/block/dasd_ioctl.c
+++ b/drivers/s390/block/dasd_ioctl.c
@@ -552,10 +552,10 @@ static int __dasd_ioctl_information(struct dasd_block *block,
 
 	memcpy(dasd_info->type, base->discipline->name, 4);
 
-	spin_lock_irqsave(&block->queue_lock, flags);
+	spin_lock_irqsave(get_ccwdev_lock(base->cdev), flags);
 	list_for_each(l, &base->ccw_queue)
 		dasd_info->chanq_len++;
-	spin_unlock_irqrestore(&block->queue_lock, flags);
+	spin_unlock_irqrestore(get_ccwdev_lock(base->cdev), flags);
 	return 0;
 }
 
-- 
2.39.2

Re: [PATCH 0/1] s390/dasd: fix locking error

[Jens Axboe]

On Fri, 09 Jun 2023 17:37:49 +0200, Stefan Haberland wrote:
> please apply the following patch that fixes a locking error in the DASD
> driver. Thanks.
> 
> Jan Höppner (1):
>   s390/dasd: Use correct lock while counting channel queue length
> 
> drivers/s390/block/dasd_ioctl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> [...]

Applied, thanks!

[1/1] s390/dasd: Use correct lock while counting channel queue length
      commit: ccc45cb4e7271c74dbb27776ae8f73d84557f5c6

Best regards,
-- 
Jens Axboe