bonding: fix two race conditions in bond_store_updelay/downdelay

[ Upstream commit b869ccfab1e324507fa3596e3e1308444fb68227 ]

This patch fixes two race conditions between bond_store_updelay/downdelay
and bond_store_miimon which could lead to division by zero as miimon can
be set to 0 while either updelay/downdelay are being set and thus miss the
zero check in the beginning, the zero div happens because updelay/downdelay
are stored as new_value / bond->params.miimon. Use rtnl to synchronize with
miimon setting.

CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Acked-by: Veaceslav Falico <vfalico@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index aae24d1..cf95bd8 100644 (file)
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -694,6 +694,8 @@ static ssize_t bonding_store_downdelay(struct device *d,
        int new_value, ret = count;
        struct bonding *bond = to_bond(d);
 
+       if (!rtnl_trylock())
+               return restart_syscall();
        if (!(bond->params.miimon)) {
                pr_err("%s: Unable to set down delay as MII monitoring is disabled\n",
                       bond->dev->name);
@@ -727,6 +729,7 @@ static ssize_t bonding_store_downdelay(struct device *d,
        }
 
 out:
+       rtnl_unlock();
        return ret;
 }
 static DEVICE_ATTR(downdelay, S_IRUGO | S_IWUSR,
@@ -749,6 +752,8 @@ static ssize_t bonding_store_updelay(struct device *d,
        int new_value, ret = count;
        struct bonding *bond = to_bond(d);
 
+       if (!rtnl_trylock())
+               return restart_syscall();
        if (!(bond->params.miimon)) {
                pr_err("%s: Unable to set up delay as MII monitoring is disabled\n",
                       bond->dev->name);
@@ -782,6 +787,7 @@ static ssize_t bonding_store_updelay(struct device *d,
        }
 
 out:
+       rtnl_unlock();
        return ret;
 }
 static DEVICE_ATTR(updelay, S_IRUGO | S_IWUSR,