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 c91f6df2db4972d3 (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>

2 files changed, 11 insertions, 11 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index d0cbc93fcf32..515473ee52cb 100644
--- 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 a692ef49c9bb..bc131d419683 100644
--- 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;