From: Jason Wang <jasowang@redhat.com>
To: mst@redhat.com, jasowang@redhat.com
Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 6/6] vhost: don't do synchronize_rcu() in vhost_uninit_vq_maps()
Date: Tue, 23 Jul 2019 03:57:18 -0400 [thread overview]
Message-ID: <20190723075718.6275-7-jasowang@redhat.com> (raw)
In-Reply-To: <20190723075718.6275-1-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 5b8821d00fe4..a17df1f4069a 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -334,7 +334,9 @@ 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:[~2019-07-23 7:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-23 7:57 [PATCH 0/6] Fixes for meta data acceleration Jason Wang
2019-07-23 7:57 ` [PATCH 1/6] vhost: don't set uaddr for invalid address Jason Wang
2019-07-23 7:57 ` [PATCH 2/6] vhost: validate MMU notifier registration Jason Wang
2019-07-23 9:17 ` Michael S. Tsirkin
2019-07-23 13:30 ` Jason Wang
2019-07-23 7:57 ` [PATCH 3/6] vhost: fix vhost map leak Jason Wang
2019-07-23 7:57 ` [PATCH 4/6] vhost: reset invalidate_count in vhost_set_vring_num_addr() Jason Wang
2019-07-23 9:17 ` Michael S. Tsirkin
2019-07-23 13:25 ` Jason Wang
2019-07-23 7:57 ` [PATCH 5/6] vhost: mark dirty pages during map uninit Jason Wang
2019-07-23 9:17 ` Michael S. Tsirkin
2019-07-23 13:19 ` Jason Wang
2019-07-25 5:21 ` Michael S. Tsirkin
2019-07-23 7:57 ` Jason Wang [this message]
2019-07-23 9:16 ` [PATCH 6/6] vhost: don't do synchronize_rcu() in vhost_uninit_vq_maps() Michael S. Tsirkin
2019-07-23 13:16 ` Jason Wang
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