From: ebiederm@xmission•com (Eric W. Biederman)
To: David Miller <davem@davemloft•net>
Cc: <netdev@vger•kernel.org>, Arnd Bergmann <arnd@arnd•de>,
Jason Wang <jasowang@redhat•com>,
"Michael S. Tsirkin" <mst@redhat•com>,
Ian Campbell <ian.campbell@citrix•com>,
Shirly Ma <mashirley@us•ibm.com>
Subject: [PATCH 2/5] macvtap: Fix macvtap_open races in the zero copy enable code.
Date: Thu, 20 Oct 2011 07:26:39 -0700 [thread overview]
Message-ID: <m1mxcvu4bk.fsf_-_@fess.ebiederm.org> (raw)
In-Reply-To: <m1sjmnu4cm.fsf@fess.ebiederm.org> (Eric W. Biederman's message of "Thu, 20 Oct 2011 07:26:01 -0700")
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>
---
drivers/net/macvtap.c | 11 +++++------
1 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 70aa628..1d9c9c2 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -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)
--
1.7.2.5
next prev parent reply other threads:[~2011-10-20 14:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-20 14:24 [PATCH 0/5] macvtap fixes Eric W. Biederman
2011-10-20 14:26 ` [PATCH 1/5] macvtap: Close a race between macvtap_open and macvtap_dellink Eric W. Biederman
2011-10-20 14:26 ` Eric W. Biederman [this message]
2011-10-20 14:27 ` [PATCH 3/5] macvtap: Don't leak unreceived packets when we delete a macvtap device Eric W. Biederman
2011-10-20 14:28 ` [PATCH 4/5] macvtap: Rewrite macvtap_newlink so the error handling works Eric W. Biederman
2011-10-20 14:29 ` [PATCH 5/5] macvtap: Fix the minor device number allocation Eric W. Biederman
2011-10-21 6:56 ` [PATCH 0/5] macvtap fixes David Miller
2011-10-24 6:31 ` Michael S. Tsirkin
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