[PATCH 3.2 001/185] selinux: correct locking in selinux_netlbl_socket_connect)

Ben Hutchings
2013-12-29T02:55:34Z

From: Paul Moore <pmoore@redhat.com>

commit 42d64e1add3a1ce8a787116036163b8724362145 upstream.

The SELinux/NetLabel glue code has a locking bug that affects systems
with NetLabel enabled, see the kernel error message below. This patch
corrects this problem by converting the bottom half socket lock to a
more conventional, and correct for this call-path, lock_sock() call.

===============================
[ INFO: suspicious RCU usage. ]
3.11.0-rc3+ #19 Not tainted
-------------------------------
net/ipv4/cipso_ipv4.c:1928 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 0
2 locks held by ping/731:
#0: (slock-AF_INET/1){+.-...}, at: [...] selinux_netlbl_socket_connect
#1: (rcu_read_lock){.+.+..}, at: [<...>] netlbl_conn_setattr

stack backtrace:
CPU: 1 PID: 731 Comm: ping Not tainted 3.11.0-rc3+ #19
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
0000000000000001 ffff88006f659d28 ffffffff81726b6a ffff88003732c500
ffff88006f659d58 ffffffff810e4457 ffff88006b845a00 0000000000000000
000000000000000c ffff880075aa2f50 ffff88006f659d90 ffffffff8169bec7
Call Trace:
[<ffffffff81726b6a>] dump_stack+0x54/0x74
[<ffffffff810e4457>] lockdep_rcu_suspicious+0xe7/0x120
[<ffffffff8169bec7>] cipso_v4_sock_setattr+0x187/0x1a0
[<ffffffff8170f317>] netlbl_conn_setattr+0x187/0x190
[<ffffffff8170f195>] ? netlbl_conn_setattr+0x5/0x190
[<ffffffff8131ac9e>] selinux_netlbl_socket_connect+0xae/0xc0
[<ffffffff81303025>] selinux_socket_connect+0x135/0x170
[<ffffffff8119d127>] ? might_fault+0x57/0xb0
[<ffffffff812fb146>] security_socket_connect+0x16/0x20
[<ffffffff815d3ad3>] SYSC_connect+0x73/0x130
[<ffffffff81739a85>] ? sysret_check+0x22/0x5d
[<ffffffff810e5e2d>] ? trace_hardirqs_on_caller+0xfd/0x1c0
[<ffffffff81373d4e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[<ffffffff815d52be>] SyS_connect+0xe/0x10
[<ffffffff81739a59>] system_call_fastpath+0x16/0x1b

Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
security/selinux/netlabel.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

--- a/security/selinux/netlabel.c
+++ b/security/selinux/netlabel.c
@@ -442,8 +442,7 @@ int selinux_netlbl_socket_connect(struct
sksec->nlbl_state != NLBL_CONNLABELED)
return 0;

- local_bh_disable();
- bh_lock_sock_nested(sk);
+ lock_sock(sk);

/* connected sockets are allowed to disconnect when the address family
* is set to AF_UNSPEC, if that is what is happening we want to reset
@@ -464,7 +463,6 @@ int selinux_netlbl_socket_connect(struct
sksec->nlbl_state = NLBL_CONNLABELED;

socket_connect_return:
- bh_unlock_sock(sk);
- local_bh_enable();
+ release_sock(sk);
return rc;
}