s390/vfio-ap: Fix NULL deref in status_show() during queue probe

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When vfio_ap_mdev_probe_queue() creates the sysfs attribute group,
the queue's driver data has not yet been set. A concurrent read of
the 'status' attribute can therefore call dev_get_drvdata() and
get NULL, which is then passed directly to
vfio_ap_mdev_for_queue() where q->apqn is unconditionally
dereferenced, causing a NULL pointer dereference.

Fix this by acquiring the update locks before calling
sysfs_create_group(). The status_show() function acquires
guests_lock before reading the driver data, so any concurrent
read will block until after dev_set_drvdata() has been called
and the update locks are released.

As a bonus, the APQN no longer needs to be read from the queue
struct after allocation — it can be read directly from apdev
before allocation and stored in a local variable, which is then
assigned to q->apqn once the allocation succeeds.

Fixes: 260f3ea141 ("s390/vfio-ap: move probe and remove callbacks to vfio_ap_ops.c")
Cc: stable@vger.kernel.org
Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>

...

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Anthony Krowiak 2026-08-12 16:02:39 -04:00 • committed by Christian Borntraeger

parent 917f509bfb

commit dd6f4ef6f8

1 changed files with 29 additions and 4 deletions

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drivers/s390/crypto/vfio_ap_ops.c

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