Re: [PATCH v2] s390/vfio-ap: Fix module unload memory leak of matrix_dev

From: Tony Krowiak
Date: Fri Jun 18 2021 - 14:11:32 EST

On 6/18/21 1:12 PM, Jason J. Herne wrote:
vfio_ap_matrix_dev_release is shadowing the global matrix_dev with a NULL
pointer. Driver data for the matrix device is never set and so
dev_get_drvdata() always returns NULL. When release is called we end up
not freeing matrix_dev. The fix is to remove the shadow variable and get
the correct pointer from the device using container_of. We'll also NULL
the global to prevent any future use.

Signed-off-by: Jason J. Herne <jjherne@xxxxxxxxxxxxx>
drivers/s390/crypto/vfio_ap_drv.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index 7dc72cb718b0..40e66cb363d1 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -82,9 +82,8 @@ static void vfio_ap_queue_dev_remove(struct ap_device *apdev)
static void vfio_ap_matrix_dev_release(struct device *dev)
- struct ap_matrix_dev *matrix_dev = dev_get_drvdata(dev);
- kfree(matrix_dev);
+ kfree(container_of(dev, struct ap_matrix_dev, device));

I suppose if we're not going to assume that the release is being
called to free the global matrix_dev, then if you are going to
retrieve it using container_of(), then maybe we should verify
the retrieved pointer is the same as the global matrix_dev?

+ matrix_dev = NULL;
static int matrix_bus_match(struct device *dev, struct device_driver *drv)