Re: [PATCH] s390/vfio_ap: fix memory leak in vfio_ap device driver

From: Harald Freudenberger
Date: Wed Mar 15 2023 - 13:25:45 EST


On 2023-03-15 16:39, Tony Krowiak wrote:
The device release callback function invoked to release the matrix device
uses the dev_get_drvdata(device *dev) function to retrieve the
pointer to the vfio_matrix_dev object in order to free its storage. The
problem is, this object is not stored as drvdata with the device; since the
kfree function will accept a NULL pointer, the memory for the
vfio_matrix_dev object is never freed.

Since the device being released is contained within the vfio_matrix_dev
object, the container_of macro will be used to retrieve its pointer.

Fixes: 1fde573413b5 ("s390: vfio-ap: base implementation of VFIO AP
device driver")
Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
---
drivers/s390/crypto/vfio_ap_drv.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_drv.c
b/drivers/s390/crypto/vfio_ap_drv.c
index 997b524bdd2b..15e9de9f4574 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -54,8 +54,9 @@ static struct ap_driver vfio_ap_drv = {

static void vfio_ap_matrix_dev_release(struct device *dev)
{
- struct ap_matrix_dev *matrix_dev = dev_get_drvdata(dev);
-
+ struct ap_matrix_dev *matrix_dev = container_of(dev,
+ struct ap_matrix_dev,
+ device);
kfree(matrix_dev);
}

I needed some indirections to follow what exactly happens here and how you
fix it, but finally I got it.
Reviewed-by: Harald Freudenberger <freude@xxxxxxxxxxxxx>