Commit 0840556e authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Jakub Kicinski
Browse files

net: Protect dev->name by seqlock. 



We will convert ioctl(SIOCGARP) to RCU, and then we need to copy
dev->name which is currently protected by rtnl_lock().

This patch does the following:

  1) Add seqlock netdev_rename_lock to protect dev->name

  2) Add netdev_copy_name() that copies dev->name to buffer
     under netdev_rename_lock

  3) Use netdev_copy_name() in netdev_get_name() and drop
     devnet_rename_sem

Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/netdev/CANn89iJEWs7AYSJqGCUABeVqOCTkErponfZdT5kV-iD=-SajnQ@mail.gmail.com/


Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240430015813.71143-7-kuniyu@amazon.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a428bfc7

include/linux/netdevice.h

+1 −0
Original line number Diff line number Diff line
@@ -3136,6 +3136,7 @@ struct net_device *netdev_get_by_name(struct net *net, const char *name, 
				      netdevice_tracker *tracker, gfp_t gfp);

struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex);

struct net_device *dev_get_by_napi_id(unsigned int napi_id);

void netdev_copy_name(struct net_device *dev, char *name);



static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,

				  unsigned short type,

net/core/dev.c

+23 −4
Original line number Diff line number Diff line
@@ -940,6 +940,18 @@ struct net_device *dev_get_by_napi_id(unsigned int napi_id) 
}

EXPORT_SYMBOL(dev_get_by_napi_id);



static DEFINE_SEQLOCK(netdev_rename_lock);



void netdev_copy_name(struct net_device *dev, char *name)

{

	unsigned int seq;



	do {

		seq = read_seqbegin(&netdev_rename_lock);

		strscpy(name, dev->name, IFNAMSIZ);

	} while (read_seqretry(&netdev_rename_lock, seq));

}



/**

 *	netdev_get_name - get a netdevice name, knowing its ifindex.

 *	@net: network namespace
@@ -951,7 +963,6 @@ int netdev_get_name(struct net *net, char *name, int ifindex) 
	struct net_device *dev;

	int ret;



	down_read(&devnet_rename_sem);

	rcu_read_lock();



	dev = dev_get_by_index_rcu(net, ifindex);
@@ -960,12 +971,11 @@ int netdev_get_name(struct net *net, char *name, int ifindex) 
		goto out;

	}



	strcpy(name, dev->name);

	netdev_copy_name(dev, name);



	ret = 0;

out:

	rcu_read_unlock();

	up_read(&devnet_rename_sem);

	return ret;

}
@@ -1217,7 +1227,10 @@ int dev_change_name(struct net_device *dev, const char *newname) 


	memcpy(oldname, dev->name, IFNAMSIZ);



	write_seqlock(&netdev_rename_lock);

	err = dev_get_valid_name(net, dev, newname);

	write_sequnlock(&netdev_rename_lock);



	if (err < 0) {

		up_write(&devnet_rename_sem);

		return err;
@@ -1257,7 +1270,9 @@ int dev_change_name(struct net_device *dev, const char *newname) 
		if (err >= 0) {

			err = ret;

			down_write(&devnet_rename_sem);

			write_seqlock(&netdev_rename_lock);

			memcpy(dev->name, oldname, IFNAMSIZ);

			write_sequnlock(&netdev_rename_lock);

			memcpy(oldname, newname, IFNAMSIZ);

			WRITE_ONCE(dev->name_assign_type, old_assign_type);

			old_assign_type = NET_NAME_RENAMED;
@@ -11403,8 +11418,12 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net, 
	dev_net_set(dev, net);

	dev->ifindex = new_ifindex;



	if (new_name[0]) /* Rename the netdev to prepared name */

	if (new_name[0]) {

		/* Rename the netdev to prepared name */

		write_seqlock(&netdev_rename_lock);

		strscpy(dev->name, new_name, IFNAMSIZ);

		write_sequnlock(&netdev_rename_lock);

	}



	/* Fixup kobjects */

	dev_set_uevent_suppress(&dev->dev, 1);