Re: [PATCH v2 7/8] s390/vfio-ap: Fix required lock not held during display of sysfs status attribute

[Anthony Krowiak <akrowiak@linux.ibm.com>]

On 8/11/26 2:20 PM, Matthew Rosato wrote:
> On 8/11/26 2:03 PM, Matthew Rosato wrote:
>> On 8/10/26 3:22 PM, Anthony Krowiak wrote:
>>> The status_show function that supports display of the status attribute of
>>> the devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue
>>> function which iterates the matrix_dev->mdev_list to find the object
>>> representing the queue device whose status is to be displayed. In order to
>>> traverse this list, the matrix_dev->guests_lock mutex must be held which is
>>> not the case.
>>>
>>> To fix this, the guests_lock mutex is taken prior to taking the
>>> matrix_dev->mdevs_lock mutex in the status_show function. It is taken
>>> there rather than the vfio_ap_mdev_for_queue function - where it is
>>> needed - because it must be taken prior to the mdevs_lock mutex in order to
>>> adhere to the proper locking order and prevent a lockdep splat; also
>>> because the mdevs_lock is needed there to access fields within
>>> the matrix_mdev object in that function.
>>>
>>> Fixes: f139862b92cf ("s390/vfio-ap: add status attribute to AP queue device's sysfs dir")
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
>> Please see my comment on patch 3.
> Also same idea here, I don't believe the pre-existing finding from
> Sashiko against this patch is resolved by this series, so have a look
> and consider a follow-on patch if it's a valid report.

Can you be more specific as to which Sashiko finding you are talking about?