linux-kernel - [ 076/143] bonding: fix two race conditions in bond_store

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Message-Id: <20140512003203.792818004@1wt.eu>
Date:	Mon, 12 May 2014 02:33:16 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Veaceslav Falico <vfalico@...hat.com>,
	Nikolay Aleksandrov <nikolay@...hat.com>,
	"David S. Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu>
Subject: [ 076/143] bonding: fix two race conditions in bond_store_updelay/downdelay

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

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

From: Nikolay Aleksandrov <nikolay@...hat.com>

[ 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@...ibm.com>
CC: Andy Gospodarek <andy@...yhouse.net>
CC: Veaceslav Falico <vfalico@...hat.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@...hat.com>
Acked-by: Veaceslav Falico <vfalico@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Willy Tarreau <w@....eu>
---
 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 8762a27..3666a9a 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -755,6 +755,8 @@ 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(DRV_NAME
 		       ": %s: Unable to set down delay as MII monitoring is disabled\n",
@@ -795,6 +797,7 @@ static ssize_t bonding_store_downdelay(struct device *d,
 	}
 
 out:
+	rtnl_unlock();
 	return ret;
 }
 static DEVICE_ATTR(downdelay, S_IRUGO | S_IWUSR,
@@ -817,6 +820,8 @@ 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(DRV_NAME
 		       ": %s: Unable to set up delay as MII monitoring is disabled\n",
@@ -856,6 +861,7 @@ static ssize_t bonding_store_updelay(struct device *d,
 	}
 
 out:
+	rtnl_unlock();
 	return ret;
 }
 static DEVICE_ATTR(updelay, S_IRUGO | S_IWUSR,
-- 
1.7.12.2.21.g234cd45.dirty



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