[PATCH 1/2] netns: Fail conspicously if someone uses net_generic at an inappropriate time.

From: ebiederm@xmission.com (Eric W. Biederman)
To: David Miller <davem@davemloft.net>
Cc: eric.dumazet@gmail.com, xemul@parallels.com,
	sjur.brandeland@stericsson.com, levinsasha928@gmail.com,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	davej@redhat.com, sjurbren@gmail.com
Subject: [PATCH 1/2] netns: Fail conspicously if someone uses net_generic at an inappropriate time.
Date: Thu, 26 Jan 2012 16:02:55 -0800	[thread overview]
Message-ID: <m1ehumc8r4.fsf_-_@fess.ebiederm.org> (raw)
In-Reply-To: <20120126.180754.679593869814492219.davem@davemloft.net> (David Miller's message of "Thu, 26 Jan 2012 18:07:54 -0500 (EST)")


By definition net_generic should never be called when it can return
NULL.  Fail conspicously with a BUG_ON to make it clear when people mess
up that a NULL return should never happen.

Recently there was a bug in the CAIF subsystem where it was registered
with register_pernet_device instead of register_pernet_subsys.  It was
erroneously concluded that net_generic could validly return NULL and
that net_assign_generic was buggy (when it was just inefficient).
Hopefully this BUG_ON will prevent people to coming to similar erroneous
conclusions in the futrue.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 include/net/netns/generic.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/include/net/netns/generic.h b/include/net/netns/generic.h
index 3419bf5..d55f434 100644
--- a/include/net/netns/generic.h
+++ b/include/net/netns/generic.h
@@ -41,6 +41,7 @@ static inline void *net_generic(const struct net *net, int id)
 	ptr = ng->ptr[id - 1];
 	rcu_read_unlock();
 
+	BUG_ON(!ptr);
 	return ptr;
 }
 #endif
-- 
1.7.2.5

