[PATCH v2 2/2] vhost: Don't call log_access_ok() when using IOTLB

[Greg Kurz]

When the IOTLB device is enabled, the log_guest_addr that is passed by
userspace to the VHOST_SET_VRING_ADDR ioctl, and which is then written
to vq->log_addr, is a GIOVA. All writes to this address are translated
by log_user() to writes to an HVA, and then ultimately logged through
the corresponding GPAs in log_write_hva(). No logging will ever occur
with vq->log_addr in this case. It is thus wrong to pass vq->log_addr
and log_guest_addr to log_access_vq() which assumes they are actual
GPAs.

Introduce a new vq_log_used_access_ok() helper that only checks accesses
to the log for the used structure when there isn't an IOTLB device around.

Signed-off-by: Greg Kurz <groug@kaod.org>
---
 drivers/vhost/vhost.c |   23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c3b49975dc28..5996e32fa818 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1370,6 +1370,20 @@ bool vhost_log_access_ok(struct vhost_dev *dev)
 }
 EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 
+static bool vq_log_used_access_ok(struct vhost_virtqueue *vq,
+                                 void __user *log_base,
+                                 bool log_used,
+                                 u64 log_addr,
+                                 size_t log_size)
+{
+       /* If an IOTLB device is present, log_addr is a GIOVA that
+        * will never be logged by log_used(). */
+       if (vq->iotlb)
+               return true;
+
+       return !log_used || log_access_ok(log_base, log_addr, log_size);
+}
+
 /* Verify access for write logging. */
 /* Caller should have vq mutex and device mutex */
 static bool vq_log_access_ok(struct vhost_virtqueue *vq,
@@ -1377,8 +1391,8 @@ static bool vq_log_access_ok(struct vhost_virtqueue *vq,
 {
        return vq_memory_access_ok(log_base, vq->umem,
                                   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
-               (!vq->log_used || log_access_ok(log_base, vq->log_addr,
-                                 vhost_get_used_size(vq, vq->num)));
+               vq_log_used_access_ok(vq, log_base, vq->log_used, vq->log_addr,
+                                     vhost_get_used_size(vq, vq->num));
 }
 
 /* Can we start vq? */
@@ -1517,8 +1531,9 @@ static long vhost_vring_set_addr(struct vhost_dev *d,
                        return -EINVAL;
 
                /* Also validate log access for used ring if enabled. */
-               if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
-                       !log_access_ok(vq->log_base, a.log_guest_addr,
+               if (!vq_log_used_access_ok(vq, vq->log_base,
+                               a.flags & (0x1 << VHOST_VRING_F_LOG),
+                               a.log_guest_addr,
                                sizeof *vq->used +
                                vq->num * sizeof *vq->used->ring))
                        return -EINVAL;