bonding: fix store_arp_validate race with mode change

We need to protect store_arp_validate via rtnl because it can race with
mode changing and we can end up having arp_validate set in a mode
different from active-backup.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Acked-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index ce4677668e2c..4e386836d34f 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -419,27 +419,33 @@ static ssize_t bonding_store_arp_validate(struct device *d,
                                           struct device_attribute *attr,
                                           const char *buf, size_t count)
 {
-        int new_value;
+        int new_value, ret = count;
         struct bonding *bond = to_bond(d);
 
+        if (!rtnl_trylock())
+                return restart_syscall();
         new_value = bond_parse_parm(buf, arp_validate_tbl);
         if (new_value < 0) {
                 pr_err("%s: Ignoring invalid arp_validate value %s\n",
                        bond->dev->name, buf);
-                return -EINVAL;
+                ret = -EINVAL;
+                goto out;
         }
         if (new_value && (bond->params.mode != BOND_MODE_ACTIVEBACKUP)) {
                 pr_err("%s: arp_validate only supported in active-backup mode.\n",
                        bond->dev->name);
-                return -EINVAL;
+                ret = -EINVAL;
+                goto out;
         }
         pr_info("%s: setting arp_validate to %s (%d).\n",
                 bond->dev->name, arp_validate_tbl[new_value].modename,
                 new_value);
 
         bond->params.arp_validate = new_value;
+out:
+        rtnl_unlock();
 
-        return count;
+        return ret;
 }
 
 static DEVICE_ATTR(arp_validate, S_IRUGO | S_IWUSR, bonding_show_arp_validate,