[kernel] Add patch from Dave Jones to fix suspicious RCU usage in SELinux (rhbz 846037)

[Josh Boyer]

commit 7051aa7c8d04c3bf80f517ec3a0f542c191f92f5
Author: Josh Boyer <jwboyer at redhat.com>
Date:   Tue Aug 21 13:18:03 2012 -0400

    Add patch from Dave Jones to fix suspicious RCU usage in SELinux (rhbz 846037)

 kernel.spec                                        |    7 +++
 ...netnode_insert-suspicious-rcu-dereference.patch |   54 ++++++++++++++++++++
 2 files changed, 61 insertions(+), 0 deletions(-)
---
diff --git a/kernel.spec b/kernel.spec
index 5fd90d0..9d3cc34 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -752,6 +752,9 @@ Patch22065: fbcon-fix-race-condition-between-console-lock-and-cursor-timer.patch
 #rhbz 847548
 Patch22066: virtio-scsi-Initialize-scatterlist-structure.patch
 
+#rhbz 846037
+Patch22067: selinux-Fix-sel_netnode_insert-suspicious-rcu-dereference.patch
+
 # END OF PATCH DEFINITIONS
 
 %endif
@@ -1447,6 +1450,9 @@ ApplyPatch fbcon-fix-race-condition-between-console-lock-and-cursor-timer.patch
 #rhbz 847548
 ApplyPatch virtio-scsi-Initialize-scatterlist-structure.patch
 
+#rhbz 846037
+ApplyPatch selinux-Fix-sel_netnode_insert-suspicious-rcu-dereference.patch
+
 # END OF PATCH APPLICATIONS
 
 %endif
@@ -2310,6 +2316,7 @@ fi
 #                 ||     ||
 %changelog
 * Tue Aug 21 2012 Josh Boyer <jwboyer at redhat.com>
+- Add patch from Dave Jones to fix suspicious RCU usage in SELinux (rhbz 846037)
 - Add patch from Richard W.M. Jones to fix virtio scsi oops (rhbz 847548)
 - Add patch from Dave Airlie to fix fb cursor vs grub2 gfxterm hang
 
diff --git a/selinux-Fix-sel_netnode_insert-suspicious-rcu-dereference.patch b/selinux-Fix-sel_netnode_insert-suspicious-rcu-dereference.patch
new file mode 100644
index 0000000..43fddf7
--- /dev/null
+++ b/selinux-Fix-sel_netnode_insert-suspicious-rcu-dereference.patch
@@ -0,0 +1,54 @@
+From: Dave Jones <>
+Subject: Fix sel_netnode_insert suspicious rcu dereference.
+	
+
+I reported this a year ago (https://lkml.org/lkml/2011/4/20/308).
+It's still a problem apparently ...
+
+===============================
+[ INFO: suspicious RCU usage. ]
+3.5.0-rc1+ #63 Not tainted
+-------------------------------
+security/selinux/netnode.c:178 suspicious rcu_dereference_check() usage!
+other info that might help us debug this:
+
+
+rcu_scheduler_active = 1, debug_locks = 0
+1 lock held by trinity-child1/8750:
+ #0:  (sel_netnode_lock){+.....}, at: [<ffffffff812d8f8a>] sel_netnode_sid+0x16a/0x3e0
+stack backtrace:
+Pid: 8750, comm: trinity-child1 Not tainted 3.5.0-rc1+ #63
+Call Trace:
+ [<ffffffff810cec2d>] lockdep_rcu_suspicious+0xfd/0x130
+ [<ffffffff812d91d1>] sel_netnode_sid+0x3b1/0x3e0
+ [<ffffffff812d8e20>] ? sel_netnode_find+0x1a0/0x1a0
+ [<ffffffff812d24a6>] selinux_socket_bind+0xf6/0x2c0
+ [<ffffffff810cd1dd>] ? trace_hardirqs_off+0xd/0x10
+ [<ffffffff810cdb55>] ? lock_release_holdtime.part.9+0x15/0x1a0
+ [<ffffffff81093841>] ? lock_hrtimer_base+0x31/0x60
+ [<ffffffff812c9536>] security_socket_bind+0x16/0x20
+ [<ffffffff815550ca>] sys_bind+0x7a/0x100
+ [<ffffffff816c03d5>] ? sysret_check+0x22/0x5d
+ [<ffffffff810d392d>] ? trace_hardirqs_on_caller+0x10d/0x1a0
+ [<ffffffff8133b09e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
+ [<ffffffff816c03a9>] system_call_fastpath+0x16/0x1b
+This patch below does what Paul McKenney suggested in the previous thread.
+
+Signed-off-by: Dave Jones <davej at redhat.com>
+
+diff --git a/security/selinux/netnode.c b/security/selinux/netnode.c
+index 28f911c..c5454c0 100644
+--- a/security/selinux/netnode.c
++++ b/security/selinux/netnode.c
+@@ -174,7 +174,8 @@ static void sel_netnode_insert(struct sel_netnode *node)
+ 	if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
+ 		struct sel_netnode *tail;
+ 		tail = list_entry(
+-			rcu_dereference(sel_netnode_hash[idx].list.prev),
++			rcu_dereference_protected(sel_netnode_hash[idx].list.prev,
++						  lockdep_is_held(&sel_netnode_lock)),
+ 			struct sel_netnode, list);
+ 		list_del_rcu(&tail->list);
+ 		kfree_rcu(tail, rcu);
+
+