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: 7eb781b1bbb7 ("virtio_mmio: add cleanup for virtio_mmio_probe")
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_mmio.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index a46a4a29e929..97760f611295 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -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;
--
2.35.1
