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 94f1b8ab8fcc4410 (sockopt: Change getsockopt() of
SO_BINDTODEVICE to return an interface name)

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Brian Haley <brian.haley@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 02e0f6b156c3f2dc7c2cae5c663cbdbfd6341484..c599e4782d454cc853a6a9c1491f38bd1c1509b4 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -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)                \

diff --git a/net/core/dev.c b/net/core/dev.c
index d0cbc93fcf32d94db2b909274dd60a9fe88cc80e..515473ee52cbb6327a9310922d0fb1c3d763df2f 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -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)))

diff --git a/net/core/sock.c b/net/core/sock.c
index a692ef49c9bb9b2d996f0538049a135a93c26812..bc131d419683c11bd6f098c930e7d4f3cd9fb697 100644 (file)
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -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;