Commit 30e6c9fa authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: devnet_rename_seq should be a seqcount 



Using a seqlock for devnet_rename_seq is not a good idea,
as device_rename() can sleep.

As we hold RTNL, we dont need a protection for writers,
and only need a seqcount so that readers can catch a change done
by a writer.

Bug added in commit c91f6df2 (sockopt: Change getsockopt() of
SO_BINDTODEVICE to return an interface name)

Reported-by: default avatarDave Jones <davej@redhat.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Brian Haley <brian.haley@hp.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f7e75ba1

include/linux/netdevice.h

+1 −1
Original line number Diff line number Diff line
@@ -1576,7 +1576,7 @@ extern int call_netdevice_notifiers(unsigned long val, struct net_device *dev); 


extern rwlock_t				dev_base_lock;		/* Device list lock */



extern seqlock_t	devnet_rename_seq;	/* Device rename lock */

extern seqcount_t	devnet_rename_seq;	/* Device rename seq */





#define for_each_netdev(net, d)		\

net/core/dev.c

+9 −9
Original line number Diff line number Diff line
@@ -203,7 +203,7 @@ static struct list_head offload_base __read_mostly; 
DEFINE_RWLOCK(dev_base_lock);

EXPORT_SYMBOL(dev_base_lock);



DEFINE_SEQLOCK(devnet_rename_seq);

seqcount_t devnet_rename_seq;



static inline void dev_base_seq_inc(struct net *net)

{
@@ -1093,10 +1093,10 @@ int dev_change_name(struct net_device *dev, const char *newname) 
	if (dev->flags & IFF_UP)

		return -EBUSY;



	write_seqlock(&devnet_rename_seq);

	write_seqcount_begin(&devnet_rename_seq);



	if (strncmp(newname, dev->name, IFNAMSIZ) == 0) {

		write_sequnlock(&devnet_rename_seq);

		write_seqcount_end(&devnet_rename_seq);

		return 0;

	}
@@ -1104,7 +1104,7 @@ int dev_change_name(struct net_device *dev, const char *newname) 


	err = dev_get_valid_name(net, dev, newname);

	if (err < 0) {

		write_sequnlock(&devnet_rename_seq);

		write_seqcount_end(&devnet_rename_seq);

		return err;

	}
@@ -1112,11 +1112,11 @@ rollback: 
	ret = device_rename(&dev->dev, dev->name);

	if (ret) {

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

		write_sequnlock(&devnet_rename_seq);

		write_seqcount_end(&devnet_rename_seq);

		return ret;

	}



	write_sequnlock(&devnet_rename_seq);

	write_seqcount_end(&devnet_rename_seq);



	write_lock_bh(&dev_base_lock);

	hlist_del_rcu(&dev->name_hlist);
@@ -1135,7 +1135,7 @@ rollback: 
		/* err >= 0 after dev_alloc_name() or stores the first errno */

		if (err >= 0) {

			err = ret;

			write_seqlock(&devnet_rename_seq);

			write_seqcount_begin(&devnet_rename_seq);

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

			goto rollback;

		} else {
@@ -4180,7 +4180,7 @@ static int dev_ifname(struct net *net, struct ifreq __user *arg) 
		return -EFAULT;



retry:

	seq = read_seqbegin(&devnet_rename_seq);

	seq = read_seqcount_begin(&devnet_rename_seq);

	rcu_read_lock();

	dev = dev_get_by_index_rcu(net, ifr.ifr_ifindex);

	if (!dev) {
@@ -4190,7 +4190,7 @@ retry: 


	strcpy(ifr.ifr_name, dev->name);

	rcu_read_unlock();

	if (read_seqretry(&devnet_rename_seq, seq))

	if (read_seqcount_retry(&devnet_rename_seq, seq))

		goto retry;



	if (copy_to_user(arg, &ifr, sizeof(struct ifreq)))

net/core/sock.c

+2 −2
Original line number Diff line number Diff line
@@ -583,7 +583,7 @@ static int sock_getbindtodevice(struct sock *sk, char __user *optval, 
		goto out;



retry:

	seq = read_seqbegin(&devnet_rename_seq);

	seq = read_seqcount_begin(&devnet_rename_seq);

	rcu_read_lock();

	dev = dev_get_by_index_rcu(net, sk->sk_bound_dev_if);

	ret = -ENODEV;
@@ -594,7 +594,7 @@ retry: 


	strcpy(devname, dev->name);

	rcu_read_unlock();

	if (read_seqretry(&devnet_rename_seq, seq))

	if (read_seqcount_retry(&devnet_rename_seq, seq))

		goto retry;



	len = strlen(devname) + 1;

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