[PATCH 5.10 491/717] virtio_ring: Fix two use after free bugs

Greg Kroah-Hartman
2020-12-28T14:22:34Z

From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit e152d8af4220a05c9797591609151d404866beaa ]

The "vq" struct is added to the "vdev->vqs" list prematurely. If we
encounter an error later in the function then the "vq" is freed, but
since it is still on the list that could lead to a use after free bug.

Fixes: cbeedb72b97a ("virtio_ring: allocate desc state for split ring separately")
Reported-by: Robert Buhren <robert.buhren@sect.tu-berlin.de>
Reported-by: Felicitas Hetzelt <file@sect.tu-berlin.de>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/X8pGaG/zkI3jk8mk@mwanda
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/virtio/virtio_ring.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 924b6b85376bd..71e16b53e9c18 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1608,7 +1608,6 @@ static struct virtqueue *vring_create_virtqueue_packed(
vq->num_added = 0;
vq->packed_ring = true;
vq->use_dma_api = vring_use_dma_api(vdev);
- list_add_tail(&vq->vq.list, &vdev->vqs);
#ifdef DEBUG
vq->in_use = false;
vq->last_add_time_valid = false;
@@ -1669,6 +1668,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
cpu_to_le16(vq->packed.event_flags_shadow);
}

+ list_add_tail(&vq->vq.list, &vdev->vqs);
return &vq->vq;

err_desc_extra:
@@ -2085,7 +2085,6 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
vq->last_used_idx = 0;
vq->num_added = 0;
vq->use_dma_api = vring_use_dma_api(vdev);
- list_add_tail(&vq->vq.list, &vdev->vqs);
#ifdef DEBUG
vq->in_use = false;
vq->last_add_time_valid = false;
@@ -2127,6 +2126,7 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
memset(vq->split.desc_state, 0, vring.num *
sizeof(struct vring_desc_state_split));

+ list_add_tail(&vq->vq.list, &vdev->vqs);
return &vq->vq;
}
EXPORT_SYMBOL_GPL(__vring_new_virtqueue);
--
2.27.0