Commit c7d52737 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net-sysfs: use dev_addr_sem to remove races in address_show() 

Using dev_base_lock is not preventing from reading garbage.

Use dev_addr_sem instead.

v4: place dev_addr_sem extern in net/core/dev.h (Jakub Kicinski)
 Link: https://lore.kernel.org/netdev/20240212175845.10f6680a@kernel.org/



Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 12692e3d

net/core/dev.c

+1 −1
Original line number Diff line number Diff line
@@ -8993,7 +8993,7 @@ int dev_set_mac_address(struct net_device *dev, struct sockaddr *sa, 
}

EXPORT_SYMBOL(dev_set_mac_address);



static DECLARE_RWSEM(dev_addr_sem);

DECLARE_RWSEM(dev_addr_sem);



int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,

			     struct netlink_ext_ack *extack)

net/core/dev.h

+3 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
#define _NET_CORE_DEV_H



#include <linux/types.h>

#include <linux/rwsem.h>



struct net;

struct net_device;
@@ -46,6 +47,8 @@ extern int weight_p; 
extern int		dev_weight_rx_bias;

extern int		dev_weight_tx_bias;



extern struct rw_semaphore dev_addr_sem;



/* rtnl helpers */

extern struct list_head net_todo_list;

void netdev_run_todo(void);

net/core/net-sysfs.c

+7 −3
Original line number Diff line number Diff line
@@ -142,17 +142,21 @@ static ssize_t name_assign_type_show(struct device *dev, 
}

static DEVICE_ATTR_RO(name_assign_type);



/* use same locking rules as GIFHWADDR ioctl's */

/* use same locking rules as GIFHWADDR ioctl's (dev_get_mac_address()) */

static ssize_t address_show(struct device *dev, struct device_attribute *attr,

			    char *buf)

{

	struct net_device *ndev = to_net_dev(dev);

	ssize_t ret = -EINVAL;



	read_lock(&dev_base_lock);

	down_read(&dev_addr_sem);



	rcu_read_lock();

	if (dev_isalive(ndev))

		ret = sysfs_format_mac(buf, ndev->dev_addr, ndev->addr_len);

	read_unlock(&dev_base_lock);

	rcu_read_unlock();



	up_read(&dev_addr_sem);

	return ret;

}

static DEVICE_ATTR_RO(address);