Commit 55c91fed authored by Wolfram Sang's avatar Wolfram Sang Committed by Michael S. Tsirkin
Browse files

virtio-mmio: don't break lifecycle of vm_dev 



vm_dev has a separate lifecycle because it has a 'struct device'
embedded. Thus, having a release callback for it is correct.

Allocating the vm_dev struct with devres totally breaks this protection,
though. Instead of waiting for the vm_dev release callback, the memory
is freed when the platform_device is removed. Resulting in a
use-after-free when finally the callback is to be called.

To easily see the problem, compile the kernel with
CONFIG_DEBUG_KOBJECT_RELEASE and unbind with sysfs.

The fix is easy, don't use devres in this case.

Found during my research about object lifetime problems.

Fixes: 7eb781b1 ("virtio_mmio: add cleanup for virtio_mmio_probe")
Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Message-Id: <20230629120526.7184-1-wsa+renesas@sang-engineering.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 52a93d39

drivers/virtio/virtio_mmio.c

+2 −3
Original line number Diff line number Diff line
@@ -607,9 +607,8 @@ static void virtio_mmio_release_dev(struct device *_d) 
	struct virtio_device *vdev =

			container_of(_d, struct virtio_device, dev);

	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

	struct platform_device *pdev = vm_dev->pdev;



	devm_kfree(&pdev->dev, vm_dev);

	kfree(vm_dev);

}



/* Platform device */
@@ -620,7 +619,7 @@ static int virtio_mmio_probe(struct platform_device *pdev) 
	unsigned long magic;

	int rc;



	vm_dev = devm_kzalloc(&pdev->dev, sizeof(*vm_dev), GFP_KERNEL);

	vm_dev = kzalloc(sizeof(*vm_dev), GFP_KERNEL);

	if (!vm_dev)

		return -ENOMEM;