netdev - [PATCH net] fou: avoid using sk_user

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Date:	Wed, 18 May 2016 17:30:16 +0900
From:	Simon Horman <simon.horman@...ronome.com>
To:	netdev@...r.kernel.org
Cc:	Tom Herbert <tom@...bertland.com>,
	Simon Horman <simon.horman@...ronome.com>
Subject: [PATCH net] fou: avoid using sk_user_data before it is initialised

During initialisation sk->sk_user_data should be initialised before
it is referenced via a call to gue_encap_init().

Found by bisection after noticing the following:

$ ip fou add port 8888 ipproto 47
[    0.383417] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[    0.384132] IP: [<ffffffff81327691>] fou_nl_cmd_add_port+0x1e1/0x230
[    0.384707] PGD 1fafc067 PUD 1fb72067 PMD 0
[    0.385110] Oops: 0002 [#1] SMP
[    0.385387] Modules linked in:
[    0.385667] CPU: 0 PID: 55 Comm: ip Not tainted 4.6.0-03623-g0b7962a6c4a3 #430
[    0.386244] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
[    0.386244] task: ffff88001fb9cac0 ti: ffff88001fbc8000 task.ti: ffff88001fbc8000
[    0.386244] RIP: 0010:[<ffffffff81327691>]  [<ffffffff81327691>] fou_nl_cmd_add_port+0x1e1/0x230
[    0.386244] RSP: 0018:ffff88001fbcbb78  EFLAGS: 00010246
[    0.386244] RAX: 0000000000000001 RBX: ffff88001fb8eb40 RCX: 000000000000002f
[    0.386244] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880019fcafc0
[    0.386244] RBP: ffff880019fcaf80 R08: ffffffff8130c370 R09: ffff880019fcaf80
[    0.386244] R10: ffff880019e12b8c R11: 0000000000000000 R12: 0000000000000004
[    0.386244] R13: 0000000000000014 R14: ffff88001fb1a300 R15: ffffffff816634c0
[    0.386244] FS:  00007f016eb4d700(0000) GS:ffff88001a200000(0000) knlGS:0000000000000000
[    0.386244] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.386244] CR2: 0000000000000008 CR3: 000000001fb69000 CR4: 00000000000006b0
[    0.386244] Stack:
[    0.386244]  ffff88001faaea24 ffff8800192426c0 00000002002f0001 0000000000000000
[    0.386244]  0000000000000000 0000000000000000 0000000000000000 000000000000b822
[    0.386244]  ffffffff81461480 ffff88001faaea14 0000000000000004 ffffffff812b0e17
[    0.386244] Call Trace:
[    0.386244]  [<ffffffff812b0e17>] ? genl_family_rcv_msg+0x197/0x320
[    0.386244]  [<ffffffff812b0fa0>] ? genl_family_rcv_msg+0x320/0x320
[    0.386244]  [<ffffffff812b1010>] ? genl_rcv_msg+0x70/0xb0
[    0.386244]  [<ffffffff812b01c1>] ? netlink_rcv_skb+0xa1/0xc0
[    0.386244]  [<ffffffff812b0c64>] ? genl_rcv+0x24/0x40
[    0.386244]  [<ffffffff812afb33>] ? netlink_unicast+0x143/0x1d0
[    0.386244]  [<ffffffff812affd6>] ? netlink_sendmsg+0x366/0x390
[    0.386244]  [<ffffffff8110a2a8>] ? rw_copy_check_uvector+0x68/0x110
[    0.386244]  [<ffffffff8126a030>] ? sock_sendmsg+0x10/0x20
[    0.386244]  [<ffffffff8126a661>] ? ___sys_sendmsg+0x1f1/0x200
[    0.386244]  [<ffffffff81110000>] ? pipe_write+0x1a0/0x420
[    0.386244]  [<ffffffff81116c32>] ? do_filp_open+0x92/0xe0
[    0.386244]  [<ffffffff8126b541>] ? __sys_sendmsg+0x41/0x70
[    0.386244]  [<ffffffff8139c81b>] ? entry_SYSCALL_64_fastpath+0x13/0x8f
[    0.386244] Code: 4c 24 12 48 8b 93 28 02 00 00 48 c7 83 68 03 00 00 e0 76 32 81 48 c7 83 78 03 00 00 50 61 32 81 48 c7 83 80 03 00 00 e0 64 32 81 <88> 4a 08 e9 20 ff ff ff 4c 89 e7 bb 8e ff ff ff e8 1a 34 07 00
[    0.386244] RIP  [<ffffffff81327691>] fou_nl_cmd_add_port+0x1e1/0x230
[    0.386244]  RSP <ffff88001fbcbb78>
[    0.386244] CR2: 0000000000000008
[    0.407176] ---[ end trace 13bf0d24a4b7f9c3 ]---

Fixes: d92283e338f6 ("fou: change to use UDP socket GRO")
Signed-off-by: Simon Horman <simon.horman@...ronome.com>
---
 net/ipv4/fou.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index eeec7d60e5fd..5f9634915cf2 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -488,6 +488,7 @@ static int fou_create(struct net *net, struct fou_cfg *cfg,
 	}
 
 	sk = sock->sk;
+	sk->sk_user_data = fou;
 
 	fou->flags = cfg->flags;
 	fou->port = cfg->udp_config.local_udp_port;
@@ -514,7 +515,6 @@ static int fou_create(struct net *net, struct fou_cfg *cfg,
 	udp_sk(sk)->encap_type = 1;
 	udp_encap_enable();
 
-	sk->sk_user_data = fou;
 	fou->sock = sock;
 
 	inet_inc_convert_csum(sk);
-- 
2.1.4