Patchwork [1/2] bonding: fix netdev event NULL pointer dereference

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Submitter Nikolay Aleksandrov
Date April 9, 2013, 8:17 p.m.
Message ID <1365538644-1502-1-git-send-email-nikolay@redhat.com>
Download mbox | patch
Permalink /patch/235226/
State Changes Requested
Delegated to: David Miller
Headers show

Comments

Nikolay Aleksandrov - April 9, 2013, 8:17 p.m.
In commit 471cb5a33dcbd7c529684a2ac7ba4451414ee4a7 ("bonding: remove
usage of dev->master") a bug was introduced which causes a NULL pointer
dereference. If a bond device is in mode 6 (ALB) and a slave is added
it will dereference a NULL pointer in bond_slave_netdev_event().
This is because in bond_enslave we have bond_alb_init_slave() which
changes the MAC address of the slave and causes a NETDEV_CHANGEADDR.
Then we have in bond_slave_netdev_event():
        struct slave *slave = bond_slave_get_rtnl(slave_dev);
        struct bonding *bond = slave->bond;
bond_slave_get_rtnl() dereferences slave_dev->rx_handler_data which at
that time is NULL since netdev_rx_handler_register() is called later.

This is fixed by checking if slave is NULL before dereferencing it.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
---
 drivers/net/bonding/bond_main.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)
Sergei Shtylyov - April 11, 2013, 1:40 p.m.
Hello.

On 10-04-2013 0:17, Nikolay Aleksandrov wrote:

> In commit 471cb5a33dcbd7c529684a2ac7ba4451414ee4a7 ("bonding: remove
> usage of dev->master") a bug was introduced which causes a NULL pointer
> dereference. If a bond device is in mode 6 (ALB) and a slave is added
> it will dereference a NULL pointer in bond_slave_netdev_event().
> This is because in bond_enslave we have bond_alb_init_slave() which
> changes the MAC address of the slave and causes a NETDEV_CHANGEADDR.
> Then we have in bond_slave_netdev_event():
>          struct slave *slave = bond_slave_get_rtnl(slave_dev);
>          struct bonding *bond = slave->bond;
> bond_slave_get_rtnl() dereferences slave_dev->rx_handler_data which at
> that time is NULL since netdev_rx_handler_register() is called later.

> This is fixed by checking if slave is NULL before dereferencing it.

> Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
[...]

    Minor formatting nit.

> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 171b10f..9995ddc 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -3168,11 +3168,21 @@ static int bond_slave_netdev_event(unsigned long event,
>   				   struct net_device *slave_dev)
>   {
>   	struct slave *slave = bond_slave_get_rtnl(slave_dev);
> -	struct bonding *bond = slave->bond;
> -	struct net_device *bond_dev = slave->bond->dev;
> +	struct bonding *bond;
> +	struct net_device *bond_dev;
>   	u32 old_speed;
>   	u8 old_duplex;
>
> +	/*
> +	 * A netdev event can be generated while enslaving a device
> +	 * before netdev_rx_handler_register is called in which case
> +	 * slave will be NULL
> +	 */

    The preferred multi-line comment style in the networking code is:

/* bla
  * bla
  */

WBR, Sergei

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Patch

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 171b10f..9995ddc 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3168,11 +3168,21 @@  static int bond_slave_netdev_event(unsigned long event,
 				   struct net_device *slave_dev)
 {
 	struct slave *slave = bond_slave_get_rtnl(slave_dev);
-	struct bonding *bond = slave->bond;
-	struct net_device *bond_dev = slave->bond->dev;
+	struct bonding *bond;
+	struct net_device *bond_dev;
 	u32 old_speed;
 	u8 old_duplex;
 
+	/*
+	 * A netdev event can be generated while enslaving a device
+	 * before netdev_rx_handler_register is called in which case
+	 * slave will be NULL
+	 */
+	if (!slave)
+		return NOTIFY_DONE;
+	bond_dev = slave->bond->dev;
+	bond = slave->bond;
+
 	switch (event) {
 	case NETDEV_UNREGISTER:
 		if (bond->setup_by_slave)