Re: [PATCH net-next] sockopt: Change getsockopt() of SO_BINDTODEVICE to return an interface name
From: Eric Dumazet <hidden>
Date: 2012-11-02 10:23:09
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
On Fri, 2012-11-02 at 13:36 +0400, Pavel Emelyanov wrote:
This still races with the device name change, potentially providing a name which never existed in the system, doesn't it?
It does. Maybe add a seqlock_t, to avoid taking rtnl here. (as it could bring interesting lockdep/deadlock issues) Here is the write side. Read side is trivial.
diff --git a/net/core/dev.c b/net/core/dev.c
index b4978e2..0184ec9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -201,6 +201,8 @@ static struct list_head ptype_all __read_mostly; /* Taps */ DEFINE_RWLOCK(dev_base_lock); EXPORT_SYMBOL(dev_base_lock); +DEFINE_SEQLOCK(devnet_rename_seq); + static inline void dev_base_seq_inc(struct net *net) { while (++net->dev_base_seq == 0);
@@ -1018,17 +1020,22 @@ int dev_change_name(struct net_device *dev, const char *newname) memcpy(oldname, dev->name, IFNAMSIZ); + write_seqlock(&devnet_rename_seq); err = dev_get_valid_name(net, dev, newname); - if (err < 0) + if (err < 0) { + write_sequnlock(&devnet_rename_seq); return err; - + } rollback: ret = device_rename(&dev->dev, dev->name); if (ret) { memcpy(dev->name, oldname, IFNAMSIZ); + write_sequnlock(&devnet_rename_seq); return ret; } + write_sequnlock(&devnet_rename_seq); + write_lock_bh(&dev_base_lock); hlist_del_rcu(&dev->name_hlist); write_unlock_bh(&dev_base_lock);
@@ -1046,6 +1053,7 @@ rollback: /* err >= 0 after dev_alloc_name() or stores the first errno */ if (err >= 0) { err = ret; + write_seqlock(&devnet_rename_seq); memcpy(dev->name, oldname, IFNAMSIZ); goto rollback; } else {