bonding: fix a race condition in calls to slave MII ioctls

In mii monitor mode, bond_check_dev_link() calls the the ioctl
handler of slave devices. It stores the ndo_do_ioctl function
pointer to a static (!) ioctl variable and later uses it to call the
handler with the IOCTL macro.

If another thread executes bond_check_dev_link() at the same time
(even with a different bond, which none of the locks prevent), a
race condition occurs. If the two racing slaves have different
drivers, this may result in one driver's ioctl handler being
called with a pointer to a net_device controlled with a different
driver, resulting in unpredictable breakage.

Unless I am overlooking something, the "static" must be a
copy'n'paste error (?).

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 3f05267..40fb5ee 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -691,7 +691,7 @@ static int bond_check_dev_link(struct bonding *bond,
                               struct net_device *slave_dev, int reporting)
 {
        const struct net_device_ops *slave_ops = slave_dev->netdev_ops;
-       static int (*ioctl)(struct net_device *, struct ifreq *, int);
+       int (*ioctl)(struct net_device *, struct ifreq *, int);
        struct ifreq ifr;
        struct mii_ioctl_data *mii;