This patch intends to fix a theoretical leak in
netfront::setup_device(), on the error path.
Suppose the frontend is in XenbusStateInitialising and the backend
advances to XenbusStateInitWait. backend_changed() will call
network_connect() -> talk_to_backend() -> setup_device().
If bind_listening_port_to_irqhandler() fails (due to event channel
allocation failure, dynamic IRQ allocation failure etc), then the grant
references and the shared ring pages remain allocated. The error
percolates back to backend_changed() without any cleanup.
backend_changed() will not change the frontend state; it will stay in
XenbusStateInitialising. If the backend retries XenbusStateInitWait
(possibly through a fake, no-op mediate state, like XenbusStateClosed),
then the frontend repeats the above call chain and leaks the previously
unreleased ring pages and grant references.
If setup_device() fails to grant access to the RX page before it tries
to call bind_listening_port_to_irqhandler(), then only the TX page /
grant reference are leaked in the next round.
I'm not sure what happens when the RX page allocation fails:
xenbus_dev_fatal() is called then, which changes the frontend's state
and seems to preclude a second immediate call to network_connect(). I
think the patch below shouldn't hurt in that case either (or after
earlier failures in setup_device() for that matter).
Thanks for considering.
Signed-off-by: Laszlo Ersek <lersek@xxxxxxxxxx>
---
drivers/xen/netfront/netfront.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff -r 415a9b435fef drivers/xen/netfront/netfront.c
--- a/drivers/xen/netfront/netfront.c Mon May 23 18:36:33 2011 +0100
+++ b/drivers/xen/netfront/netfront.c Tue May 24 11:37:12 2011 +0200
@@ -215,6 +215,7 @@ static int setup_device(struct xenbus_de
static struct net_device *create_netdev(struct xenbus_device *);
static void end_access(int, void *);
+static void netif_release_rings(struct netfront_info *);
static void netif_disconnect_backend(struct netfront_info *);
static int network_connect(struct net_device *);
@@ -522,6 +523,7 @@ static int setup_device(struct xenbus_de
return 0;
fail:
+ netif_release_rings(info);
return err;
}
@@ -2152,6 +2154,15 @@ static struct notifier_block notifier_in
};
#endif
+static void netif_release_rings(struct netfront_info *info)
+{
+ end_access(info->tx_ring_ref, info->tx.sring);
+ end_access(info->rx_ring_ref, info->rx.sring);
+ info->tx_ring_ref = GRANT_INVALID_REF;
+ info->rx_ring_ref = GRANT_INVALID_REF;
+ info->tx.sring = NULL;
+ info->rx.sring = NULL;
+}
static void netif_disconnect_backend(struct netfront_info *info)
{
@@ -2166,12 +2177,7 @@ static void netif_disconnect_backend(str
unbind_from_irqhandler(info->irq, info->netdev);
info->irq = 0;
- end_access(info->tx_ring_ref, info->tx.sring);
- end_access(info->rx_ring_ref, info->rx.sring);
- info->tx_ring_ref = GRANT_INVALID_REF;
- info->rx_ring_ref = GRANT_INVALID_REF;
- info->tx.sring = NULL;
- info->rx.sring = NULL;
+ netif_release_rings(info);
}
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