The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 0210a8db2aeca393fb3067e234967877e3146266 Mon Sep 17 00:00:00 2001 From: Greg Kurz <groug@xxxxxxxx> Date: Sat, 3 Oct 2020 12:01:52 +0200 Subject: [PATCH] vhost: Don't call access_ok() when using IOTLB When the IOTLB device is enabled, the vring addresses we get from userspace are GIOVAs. It is thus wrong to pass them down to access_ok() which only takes HVAs. Access validation is done at prefetch time with IOTLB. Teach vq_access_ok() about that by moving the (vq->iotlb) check from vhost_vq_access_ok() to vq_access_ok(). This prevents vhost_vring_set_addr() to fail when verifying the accesses. No behavior change for vhost_vq_access_ok(). BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1883084 Fixes: 6b1e6cc7855b ("vhost: new device IOTLB API") Cc: jasowang@xxxxxxxxxx CC: stable@xxxxxxxxxxxxxxx # 4.14+ Signed-off-by: Greg Kurz <groug@xxxxxxxx> Acked-by: Jason Wang <jasowang@xxxxxxxxxx> Link: https://lore.kernel.org/r/160171931213.284610.2052489816407219136.stgit@xxxxxxxxx Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index b45519ca66a7..c3b49975dc28 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1290,6 +1290,11 @@ static bool vq_access_ok(struct vhost_virtqueue *vq, unsigned int num, vring_used_t __user *used) { + /* If an IOTLB device is present, the vring addresses are + * GIOVAs. Access validation occurs at prefetch time. */ + if (vq->iotlb) + return true; + return access_ok(desc, vhost_get_desc_size(vq, num)) && access_ok(avail, vhost_get_avail_size(vq, num)) && access_ok(used, vhost_get_used_size(vq, num)); @@ -1383,10 +1388,6 @@ bool vhost_vq_access_ok(struct vhost_virtqueue *vq) if (!vq_log_access_ok(vq, vq->log_base)) return false; - /* Access validation occurs at prefetch time with IOTLB */ - if (vq->iotlb) - return true; - return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used); } EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
