[PATCH v2] iommu/virtio: Reset device before deleting virtqueues on probe failure

[PATCH v2] iommu/virtio: Reset device before deleting virtqueues on probe failure

[Yuho Choi]

viommu_probe() marks the device DRIVER_OK before populating the event
virtqueue and registering the IOMMU device in sysfs.  viommu_fill_evtq()
hands the device a set of device-writable buffers through
virtqueue_add_inbuf(), so from that point on the device may write into
them and into the rings.

If either step fails, the error path deletes the virtqueues without
resetting the device first.  The event buffers are allocated with
devm_kmalloc_array() and are released as probe unwinds, so the device can
go on writing to memory that has been freed.

Reset the device before deleting the virtqueues, the way viommu_remove()
already does.

Fixes: edcd69ab9a32 ("iommu: Add virtio-iommu driver")
Cc: stable@vger.kernel.org
Signed-off-by: Yuho Choi <oss.patchbox@gmail.com>
---
Changes in v2:
- No code change.
- Reword the commit message to explain how the device can write to the
  freed event buffers.
- Add Cc: stable.
- v1 was mistakenly posted twice; this version supersedes both postings.

v1: https://lore.kernel.org/all/20260911011249.1498825-1-oss.patchbox@gmail.com/

Compile-tested only (x86_64 allmodconfig, W=1).

 drivers/iommu/virtio-iommu.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 587fc13197f12..fa72ae23b8afa 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -1227,12 +1227,12 @@ static int viommu_probe(struct virtio_device *vdev)
 	/* Populate the event queue with buffers */
 	ret = viommu_fill_evtq(viommu);
 	if (ret)
-		goto err_free_vqs;
+		goto err_reset_vdev;
 
 	ret = iommu_device_sysfs_add(&viommu->iommu, dev, NULL, "%s",
 				     virtio_bus_name(vdev));
 	if (ret)
-		goto err_free_vqs;
+		goto err_reset_vdev;
 
 	vdev->priv = viommu;
 
@@ -1244,6 +1244,8 @@ static int viommu_probe(struct virtio_device *vdev)
 
 	return 0;
 
+err_reset_vdev:
+	virtio_reset_device(vdev);
 err_free_vqs:
 	vdev->config->del_vqs(vdev);
 

base-commit: 7704c4c5bb127673b4f0ead839919db573559e38
-- 
2.43.0