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authorMichael S. Tsirkin <mst@redhat.com>2014-02-13 11:45:11 +0200
committerDavid S. Miller <davem@davemloft.net>2014-02-13 18:47:30 -0500
commitb0c057ca7e835b36c6050c7627634b664796c1d6 (patch)
tree328353448d8946ef639ed9c0d5be239e38058859 /drivers/vhost
parent0ad8b480d6ee916aa84324f69acf690142aecd0e (diff)
downloadlinux-b0c057ca7e835b36c6050c7627634b664796c1d6.tar.bz2
vhost: fix a theoretical race in device cleanup
vhost_zerocopy_callback accesses VQ right after it drops a ubuf reference. In theory, this could race with device removal which waits on the ubuf kref, and crash on use after free. Do all accesses within rcu read side critical section, and synchronize on release. Since callbacks are always invoked from bh, synchronize_rcu_bh seems enough and will help release complete a bit faster. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/vhost')
-rw-r--r--drivers/vhost/net.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 41be4de37e81..a0fa5de210cf 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -308,6 +308,8 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
struct vhost_virtqueue *vq = ubufs->vq;
int cnt;
+ rcu_read_lock_bh();
+
/* set len to mark this desc buffers done DMA */
vq->heads[ubuf->desc].len = success ?
VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;
@@ -322,6 +324,8 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
*/
if (cnt <= 1 || !(cnt % 16))
vhost_poll_queue(&vq->poll);
+
+ rcu_read_unlock_bh();
}
/* Expects to be always run from workqueue - which acts as
@@ -799,6 +803,8 @@ static int vhost_net_release(struct inode *inode, struct file *f)
fput(tx_sock->file);
if (rx_sock)
fput(rx_sock->file);
+ /* Make sure no callbacks are outstanding */
+ synchronize_rcu_bh();
/* We do an extra flush before freeing memory,
* since jobs can re-queue themselves. */
vhost_net_flush(n);