* Re: [RFC PATCH] selinux: fix a RCU dereference in sel_netnode_insert()
[not found] <20120516201039.15853.97673.stgit@sifl>
@ 2012-05-16 20:18 ` Paul E. McKenney
0 siblings, 0 replies; only message in thread
From: Paul E. McKenney @ 2012-05-16 20:18 UTC (permalink / raw)
To: Paul Moore; +Cc: selinux, davej
On Wed, May 16, 2012 at 04:10:40PM -0400, Paul Moore wrote:
> This patch changes the rcu_dereference() call in sel_netnode_insert()
> to a rcu_dereference_protected() call to solve the problem shown
> below.
>
> ===============================
> [ INFO: suspicious RCU usage. ]
> 3.4.0-rc7+ #93 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/25132:
> #0: (sel_netnode_lock){+.....}, at:
> [<ffffffff812db738>] sel_netnode_sid+0x148/0x3c0
> stack backtrace:
> Pid: 25132, comm: trinity Not tainted 3.4.0-rc7+ #93
> Call Trace:
> [<ffffffff810cc7cd>] lockdep_rcu_suspicious+0xfd/0x130
> [<ffffffff812db981>] sel_netnode_sid+0x391/0x3c0
> [<ffffffff812db5f0>] ? sel_netnode_find+0x1a0/0x1a0
> [<ffffffff812d4a84>] selinux_socket_bind+0x104/0x350
> [<ffffffff810a6648>] ? sched_clock_cpu+0xb8/0x130
> [<ffffffff816a47b9>] ? sub_preempt_count+0xa9/0xe0
> [<ffffffff812cb3e6>] security_socket_bind+0x16/0x20
> [<ffffffff815468aa>] sys_bind+0x7a/0x100
> [<ffffffff816a8795>] ? sysret_check+0x22/0x5d
> [<ffffffff810d149d>] ? trace_hardirqs_on_caller+0x10d/0x1a0
> [<ffffffff810fc18c>] ? __audit_syscall_entry+0xcc/0x310
> [<ffffffff8133839e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> [<ffffffff816a8769>] system_call_fastpath+0x16/0x1b
>
> Reported-by: Dave Jones <davej@redhat.com>
> Signed-off-by: Paul Moore <pmoore@redhat.com>
Looks good to me!
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> --
>
> I've compiled tested this patch but due to some technical difficulties
> today I haven't been able to build a full kernel to make sure nothing
> horrible happens at boot; however, sending this out anyway in case
> others are having problems and *need* something.
> ---
> security/selinux/netnode.c | 4 +++-
> 1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/security/selinux/netnode.c b/security/selinux/netnode.c
> index 8636585..bb24c5d 100644
> --- a/security/selinux/netnode.c
> +++ b/security/selinux/netnode.c
> @@ -174,7 +174,9 @@ 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);
>
--
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