bonding: fix lock ordering for rtnl and bonding_rwsem
Fix the handling of rtnl and the bonding_rwsem to always be acquired
in a consistent order (rtnl, then bonding_rwsem).
The existing code sometimes acquired them in this order, and sometimes
in the opposite order, which opens a window for deadlock between ifenslave
and sysfs.
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 379c5d8..2c6da49 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -4874,9 +4874,22 @@
int bond_create(char *name, struct bond_params *params, struct bonding **newbond)
{
struct net_device *bond_dev;
+ struct bonding *bond, *nxt;
int res;
rtnl_lock();
+ down_write(&bonding_rwsem);
+
+ /* Check to see if the bond already exists. */
+ list_for_each_entry_safe(bond, nxt, &bond_dev_list, bond_list)
+ if (strnicmp(bond->dev->name, name, IFNAMSIZ) == 0) {
+ printk(KERN_ERR DRV_NAME
+ ": cannot add bond %s; it already exists\n",
+ name);
+ res = -EPERM;
+ goto out_rtnl;
+ }
+
bond_dev = alloc_netdev(sizeof(struct bonding), name ? name : "",
ether_setup);
if (!bond_dev) {
@@ -4915,10 +4928,12 @@
netif_carrier_off(bond_dev);
+ up_write(&bonding_rwsem);
rtnl_unlock(); /* allows sysfs registration of net device */
res = bond_create_sysfs_entry(bond_dev->priv);
if (res < 0) {
rtnl_lock();
+ down_write(&bonding_rwsem);
goto out_bond;
}
@@ -4929,6 +4944,7 @@
out_netdev:
free_netdev(bond_dev);
out_rtnl:
+ up_write(&bonding_rwsem);
rtnl_unlock();
return res;
}
@@ -4949,6 +4965,9 @@
#ifdef CONFIG_PROC_FS
bond_create_proc_dir();
#endif
+
+ init_rwsem(&bonding_rwsem);
+
for (i = 0; i < max_bonds; i++) {
res = bond_create(NULL, &bonding_defaults, NULL);
if (res)