netdev - Re: [PATCH net] bonding: fix two race conditions in bond_store

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Message-ID: <20131114101754.GR19702@redhat.com>
Date:	Thu, 14 Nov 2013 11:17:54 +0100
From:	Veaceslav Falico <vfalico@...hat.com>
To:	Nikolay Aleksandrov <nikolay@...hat.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [PATCH net] bonding: fix two race conditions in
 bond_store_updelay/downdelay

On Wed, Nov 13, 2013 at 05:07:46PM +0100, Nikolay Aleksandrov wrote:
>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>

Nice, thanks! :)

Acked-by: Veaceslav Falico <vfalico@...hat.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 bc8fd36..8f8a607 100644
>--- a/drivers/net/bonding/bond_sysfs.c
>+++ b/drivers/net/bonding/bond_sysfs.c
>@@ -701,6 +701,8 @@ 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);
>@@ -734,6 +736,7 @@ static ssize_t bonding_store_downdelay(struct device *d,
> 	}
>
> out:
>+	rtnl_unlock();
> 	return ret;
> }
> static DEVICE_ATTR(downdelay, S_IRUGO | S_IWUSR,
>@@ -756,6 +759,8 @@ 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);
>@@ -789,6 +794,7 @@ static ssize_t bonding_store_updelay(struct device *d,
> 	}
>
> out:
>+	rtnl_unlock();
> 	return ret;
> }
> static DEVICE_ATTR(updelay, S_IRUGO | S_IWUSR,
>-- 
>1.8.1.4
>
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