From: Jason Wang <jasowang@redhat.com>
To: mst@redhat.com, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, jgg@ziepe.ca,
Jason Wang <jasowang@redhat.com>
Subject: [PATCH V4 6/9] vhost: don't do synchronize_rcu() in vhost_uninit_vq_maps()
Date: Wed, 7 Aug 2019 03:06:14 -0400 [thread overview]
Message-ID: <20190807070617.23716-7-jasowang@redhat.com> (raw)
In-Reply-To: <20190807070617.23716-1-jasowang@redhat.com>
There's no need for RCU synchronization in vhost_uninit_vq_maps()
since we've already serialized with readers (memory accessors). This
also avoid the possible userspace DOS through ioctl() because of the
possible high latency caused by synchronize_rcu().
Reported-by: Michael S. Tsirkin <mst@redhat.com>
Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address")
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/vhost/vhost.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c12cdadb0855..cfc11f9ed9c9 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -333,7 +333,9 @@ static void vhost_uninit_vq_maps(struct vhost_virtqueue *vq)
}
spin_unlock(&vq->mmu_lock);
- synchronize_rcu();
+ /* No need for synchronize_rcu() or kfree_rcu() since we are
+ * serialized with memory accessors (e.g vq mutex held).
+ */
for (i = 0; i < VHOST_NUM_ADDRS; i++)
if (map[i])
--
2.18.1
next prev parent reply other threads:[~2019-08-07 7:06 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-07 7:06 [PATCH V4 0/9] Fixes for metadata accelreation Jason Wang
2019-08-07 7:06 ` [PATCH V4 1/9] vhost: don't set uaddr for invalid address Jason Wang
2019-08-07 7:06 ` [PATCH V4 2/9] vhost: validate MMU notifier registration Jason Wang
2019-08-07 7:06 ` [PATCH V4 3/9] vhost: fix vhost map leak Jason Wang
2019-08-07 7:06 ` [PATCH V4 4/9] vhost: reset invalidate_count in vhost_set_vring_num_addr() Jason Wang
2019-08-07 7:06 ` [PATCH V4 5/9] vhost: mark dirty pages during map uninit Jason Wang
2019-08-07 7:06 ` Jason Wang [this message]
2019-08-07 7:06 ` [PATCH V4 7/9] vhost: do not use RCU to synchronize MMU notifier with worker Jason Wang
2019-08-07 12:07 ` Jason Gunthorpe
2019-08-07 14:02 ` Jason Wang
2019-08-08 12:54 ` Jason Wang
2019-08-08 13:01 ` Jason Wang
2019-08-08 13:05 ` Jason Gunthorpe
2019-08-10 19:12 ` [PATCH V5 0/9] Fixes for vhost metadata acceleration Michael S. Tsirkin
2019-08-07 7:06 ` [PATCH V4 8/9] vhost: correctly set dirty pages in MMU notifiers callback Jason Wang
2019-08-07 7:06 ` [PATCH V4 9/9] vhost: do not return -EAGAIN for non blocking invalidation too early Jason Wang
2019-08-09 5:15 ` [PATCH V4 0/9] Fixes for metadata accelreation David Miller
2019-08-09 5:35 ` Jason Wang
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