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macvtap: Fix macvtap_open races in the zero copy enable code.

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To see if it is appropriate to enable the macvtap zero copy feature
don't test the lowerdev network device flags.   Instead test the
macvtap network device flags which are a direct copy of the lowerdev
flags.  This is important because nothing holds a reference to lowerdev
and on a very bad day we lowerdev could be a pointer to stale memory.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric W. Biederman 2011-10-20 04:26:39 +00:00 committed by David S. Miller
parent 99f34b38cd
commit 047af9cfed
1 changed files with 5 additions and 6 deletions
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11
drivers/net/macvtap.c
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@ -343,7 +343,6 @@ static int macvtap_open(struct inode *inode, struct file *file)
{
struct net *net = current->nsproxy->net_ns;
struct net_device *dev = dev_get_by_index(net, iminor(inode));
struct macvlan_dev *vlan = netdev_priv(dev);
struct macvtap_queue *q;
int err;
@ -376,12 +375,12 @@ static int macvtap_open(struct inode *inode, struct file *file)
/*
* so far only KVM virtio_net uses macvtap, enable zero copy between
* guest kernel and host kernel when lower device supports zerocopy
*
* The macvlan supports zerocopy iff the lower device supports zero
* copy so we don't have to look at the lower device directly.
*/
if (vlan) {
if ((vlan->lowerdev->features & NETIF_F_HIGHDMA) &&
(vlan->lowerdev->features & NETIF_F_SG))
sock_set_flag(&q->sk, SOCK_ZEROCOPY);
}
if ((dev->features & NETIF_F_HIGHDMA) && (dev->features & NETIF_F_SG))
sock_set_flag(&q->sk, SOCK_ZEROCOPY);
err = macvtap_set_queue(dev, file, q);
if (err)