4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Halil Pasic <pasic@xxxxxxxxxxxxxxxxxx>
commit cda8bba0f99d25d2061c531113c14fa41effc3ae upstream.
Currently, under certain circumstances vhost_init_is_le does just a part
of the initialization job, and depends on vhost_reset_is_le being called
too. For this reason vhost_vq_init_access used to call vhost_reset_is_le
when vq->private_data is NULL. This is not only counter intuitive, but
also real a problem because it breaks vhost_net. The bug was introduced to
vhost_net with commit 2751c9882b94 ("vhost: cross-endian support for
legacy devices"). The symptom is corruption of the vq's used.idx field
(virtio) after VHOST_NET_SET_BACKEND was issued as a part of the vhost
shutdown on a vq with pending descriptors.
Let us make sure the outcome of vhost_init_is_le never depend on the state
it is actually supposed to initialize, and fix virtio_net by removing the
reset from vhost_vq_init_access.
With the above, there is no reason for vhost_reset_is_le to do just half
of the job. Let us make vhost_reset_is_le reinitialize is_le.
Signed-off-by: Halil Pasic <pasic@xxxxxxxxxxxxxxxxxx>
Reported-by: Michael A. Tebolt <miket@xxxxxxxxxx>
Reported-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx>
Fixes: commit 2751c9882b94 ("vhost: cross-endian support for legacy devices")
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Reviewed-by: Greg Kurz <groug@xxxxxxxx>
Tested-by: Michael A. Tebolt <miket@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/vhost/vhost.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -130,14 +130,14 @@ static long vhost_get_vring_endian(struc
static void vhost_init_is_le(struct vhost_virtqueue *vq)
{
- if (vhost_has_feature(vq, VIRTIO_F_VERSION_1))
- vq->is_le = true;
+ vq->is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1)
+ || virtio_legacy_is_little_endian();
}
#endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
static void vhost_reset_is_le(struct vhost_virtqueue *vq)
{
- vq->is_le = virtio_legacy_is_little_endian();
+ vhost_init_is_le(vq);
}
struct vhost_flush_struct {
@@ -1713,10 +1713,8 @@ int vhost_vq_init_access(struct vhost_vi
int r;
bool is_le = vq->is_le;
- if (!vq->private_data) {
- vhost_reset_is_le(vq);
+ if (!vq->private_data)
return 0;
- }
vhost_init_is_le(vq);
--
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