netdev - [PATCH net] sock_diag: don't broadcast kernel sockets

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Message-Id: <1435682972-2703-1-git-send-email-kraig@google.com>
Date:	Tue, 30 Jun 2015 12:49:32 -0400
From:	Craig Gallek <kraig@...gle.com>
To:	netdev@...r.kernel.org
Cc:	davej@...emonkey.org.uk, edumazet@...gle.com,
	ebiederm@...ssion.com, davem@...emloft.net,
	Craig Gallek <kraig@...gle.com>
Subject: [PATCH net] sock_diag: don't broadcast kernel sockets

Kernel sockets do not hold a reference for the network namespace to
which they point.  Socket destruction broadcasting relies on the
network namespace and will cause the splat below when a kernel socket
is destroyed.

This fix simply ignores kernel sockets when they are destroyed.

Reported as:
general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
CPU: 1 PID: 9130 Comm: kworker/1:1 Not tainted 4.1.0-gelk-debug+ #1
Workqueue: sock_diag_events sock_diag_broadcast_destroy_work
Stack:
 ffff8800b9c586c0 ffff8800b9c586c0 ffff8800ac4692c0 ffff8800936d4a90
 ffff8800352efd38 ffffffff8469a93e ffff8800352efd98 ffffffffc09b9b90
 ffff8800352efd78 ffff8800ac4692c0 ffff8800b9c586c0 ffff8800831b6ab8
Call Trace:
 [<ffffffff8469a93e>] ? mutex_unlock+0xe/0x10
 [<ffffffffc09b9b90>] ? inet_diag_handler_get_info+0x110/0x1fb [inet_diag]
 [<ffffffff845c868d>] netlink_broadcast+0x1d/0x20
 [<ffffffff8469a93e>] ? mutex_unlock+0xe/0x10
 [<ffffffff845b2bf5>] sock_diag_broadcast_destroy_work+0xd5/0x160
 [<ffffffff8408ea97>] process_one_work+0x147/0x420
 [<ffffffff8408f0f9>] worker_thread+0x69/0x470
 [<ffffffff8409fda3>] ? preempt_count_sub+0xa3/0xf0
 [<ffffffff8408f090>] ? rescuer_thread+0x320/0x320
 [<ffffffff84093cd7>] kthread+0x107/0x120
 [<ffffffff84093bd0>] ? kthread_create_on_node+0x1b0/0x1b0
 [<ffffffff8469d31f>] ret_from_fork+0x3f/0x70
 [<ffffffff84093bd0>] ? kthread_create_on_node+0x1b0/0x1b0

Tested:
  Using a debug kernel while 'ss -E' is running:
  ip netns add test-ns
  ip netns delete test-ns

Fixes: eb4cb008529c sock_diag: define destruction multicast groups
Fixes: 26abe14379f8 net: Modify sk_alloc to not reference count the
  netns of kernel sockets.
Reported-by: Dave Jones <davej@...emonkey.org.uk>
Suggested-by: Eric Dumazet <eric.dumazet@...il.com>

Signed-off-by: Craig Gallek <kraig@...gle.com>
---
 net/core/sock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index e4be66f..08f16db 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1454,7 +1454,7 @@ void sk_destruct(struct sock *sk)
 
 static void __sk_free(struct sock *sk)
 {
-	if (unlikely(sock_diag_has_destroy_listeners(sk)))
+	if (unlikely(sock_diag_has_destroy_listeners(sk) && sk->sk_net_refcnt))
 		sock_diag_broadcast_destroy(sk);
 	else
 		sk_destruct(sk);
-- 
2.2.0.rc0.207.ga3a616c

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