From: Wolfram Sang wsa+renesas@sang-engineering.com
[ Upstream commit 55c91fedd03d7b9cf0c5199b2eb12b9b8e95281a ]
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@sang-engineering.com Message-Id: 20230629120526.7184-1-wsa+renesas@sang-engineering.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 a46a4a29e9295..97760f6112959 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;