2015-07-30 13:51:12

by Sowmini Varadhan

Subject: [PATCH v2 net] net: sk_clone_lock() should only do get_net() if the parent is not a kernel socket

The newsk returned by sk_clone_lock should hold a get_net()
reference if, and only if, the parent is not a kernel socket
(making this similar to sk_alloc()).

E.g,. for the SYN_RECV path, tcp_v4_syn_recv_sock->..inet_csk_clone_lock
sets up the syn_recv newsk from sk_clone_lock. When the parent (listen)
socket is a kernel socket (defined in sk_alloc() as having
sk_net_refcnt == 0), then the newsk should also have a 0 sk_net_refcnt
and should not hold a get_net() reference.

Fixes: 26abe14379f8 ("net: Modify sk_alloc to not reference count the
netns of kernel sockets.")
Acked-by: Eric Dumazet <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Signed-off-by: Sowmini Varadhan <[email protected]>
---
v2: pulled patch #3 out of the RFC patch-set for RDS-TCP netns fixes;
Added Fixes, Acked-by, Cc fields based on mailing list feedback
from Eric Dumazet.

net/core/sock.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 08f16db..371d1b7 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1497,7 +1497,8 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
sock_copy(newsk, sk);

/* SANITY */
- get_net(sock_net(newsk));
+ if (likely(newsk->sk_net_refcnt))
+ get_net(sock_net(newsk));
sk_node_init(&newsk->sk_node);
sock_lock_init(newsk);
bh_lock_sock(newsk);
--
1.7.1

2015-07-30 23:00:34

by David Miller

Subject: Re: [PATCH v2 net] net: sk_clone_lock() should only do get_net() if the parent is not a kernel socket

From: Sowmini Varadhan <[email protected]>
Date: Thu, 30 Jul 2015 15:50:36 +0200

>
>
> The newsk returned by sk_clone_lock should hold a get_net()
> reference if, and only if, the parent is not a kernel socket
> (making this similar to sk_alloc()).
>
> E.g,. for the SYN_RECV path, tcp_v4_syn_recv_sock->..inet_csk_clone_lock
> sets up the syn_recv newsk from sk_clone_lock. When the parent (listen)
> socket is a kernel socket (defined in sk_alloc() as having
> sk_net_refcnt == 0), then the newsk should also have a 0 sk_net_refcnt
> and should not hold a get_net() reference.
>
> Fixes: 26abe14379f8 ("net: Modify sk_alloc to not reference count the
> netns of kernel sockets.")
> Acked-by: Eric Dumazet <[email protected]>
> Cc: Eric W. Biederman <[email protected]>
> Signed-off-by: Sowmini Varadhan <[email protected]>
> ---
> v2: pulled patch #3 out of the RFC patch-set for RDS-TCP netns fixes;
> Added Fixes, Acked-by, Cc fields based on mailing list feedback
> from Eric Dumazet.

Applied, thanks everyone.