[PATCH 3.11 016/208] bonding: fix two race conditions in bond_store_updelay/downdelay

[Luis Henriques]

3.11.10.2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nikolay Aleksandrov <nikolay at redhat.com>

commit b869ccfab1e324507fa3596e3e1308444fb68227 upstream.

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 at us.ibm.com>
CC: Andy Gospodarek <andy at greyhouse.net>
CC: Veaceslav Falico <vfalico at redhat.com>
Signed-off-by: Nikolay Aleksandrov <nikolay at redhat.com>
Acked-by: Veaceslav Falico <vfalico at redhat.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/bonding/bond_sysfs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index 076f8af..ee7a5ee 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -733,6 +733,8 @@ 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);
@@ -766,6 +768,7 @@ static ssize_t bonding_store_downdelay(struct device *d,
 	}
 
 out:
+	rtnl_unlock();
 	return ret;
 }
 static DEVICE_ATTR(downdelay, S_IRUGO | S_IWUSR,
@@ -788,6 +791,8 @@ 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);
@@ -821,6 +826,7 @@ static ssize_t bonding_store_updelay(struct device *d,
 	}
 
 out:
+	rtnl_unlock();
 	return ret;
 }
 static DEVICE_ATTR(updelay, S_IRUGO | S_IWUSR,
-- 
1.8.3.2