* suspicious rcu_dereference_check in security/selinux/netnode.c
@ 2011-04-20 18:35 Dave Jones
2011-04-20 18:42 ` Eric Paris
0 siblings, 1 reply; 4+ messages in thread
From: Dave Jones @ 2011-04-20 18:35 UTC (permalink / raw)
To: sds; +Cc: jmorris, eparis, Linux Kernel
===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
security/selinux/netnode.c:193 invoked rcu_dereference_check() without protection!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
1 lock held by a.out/2018:
#0: (sel_netnode_lock){+.....}, at: [<ffffffff81212ab7>] sel_netnode_sid+0x9e/0x267
stack backtrace:
Pid: 2018, comm: a.out Not tainted 2.6.39-rc4+ #3
Call Trace:
[<ffffffff81084908>] lockdep_rcu_dereference+0xa8/0xb0
[<ffffffff81212c0d>] sel_netnode_sid+0x1f4/0x267
[<ffffffff81212a19>] ? sel_netnode_find+0xe3/0xe3
[<ffffffff8120d564>] selinux_socket_bind+0x1cf/0x26f
[<ffffffff81086c08>] ? lock_release+0x181/0x18e
[<ffffffff81100db8>] ? might_fault+0xa5/0xac
[<ffffffff81100d6f>] ? might_fault+0x5c/0xac
[<ffffffff812073f1>] security_socket_bind+0x16/0x18
[<ffffffff813ee0e9>] sys_bind+0x73/0xcf
[<ffffffff814c5d7a>] ? sysret_check+0x2e/0x69
[<ffffffff810870cf>] ? trace_hardirqs_on_caller+0x10b/0x12f
[<ffffffff810a9efb>] ? audit_syscall_entry+0x11c/0x148
[<ffffffff81255e2e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[<ffffffff814c5d42>] system_call_fastpath+0x16/0x1b
something like this perhaps ?
Dave
diff --git a/security/selinux/netnode.c b/security/selinux/netnode.c
index 65ebfe9..d0c38ba 100644
--- a/security/selinux/netnode.c
+++ b/security/selinux/netnode.c
@@ -188,9 +188,11 @@ static void sel_netnode_insert(struct sel_netnode *node)
list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
struct sel_netnode *tail;
+ rcu_read_lock();
tail = list_entry(
rcu_dereference(sel_netnode_hash[idx].list.prev),
struct sel_netnode, list);
+ rcu_read_unlock();
list_del_rcu(&tail->list);
call_rcu(&tail->rcu, sel_netnode_free);
} else
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: suspicious rcu_dereference_check in security/selinux/netnode.c
2011-04-20 18:35 suspicious rcu_dereference_check in security/selinux/netnode.c Dave Jones
@ 2011-04-20 18:42 ` Eric Paris
2011-04-20 19:29 ` Paul Moore
0 siblings, 1 reply; 4+ messages in thread
From: Eric Paris @ 2011-04-20 18:42 UTC (permalink / raw)
To: Dave Jones; +Cc: sds, jmorris, eparis, Linux Kernel, paul.moore, selinux
[added paul] EOM
On Wed, 2011-04-20 at 14:35 -0400, Dave Jones wrote:
> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> security/selinux/netnode.c:193 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 1, debug_locks = 0
> 1 lock held by a.out/2018:
> #0: (sel_netnode_lock){+.....}, at: [<ffffffff81212ab7>] sel_netnode_sid+0x9e/0x267
>
> stack backtrace:
> Pid: 2018, comm: a.out Not tainted 2.6.39-rc4+ #3
> Call Trace:
> [<ffffffff81084908>] lockdep_rcu_dereference+0xa8/0xb0
> [<ffffffff81212c0d>] sel_netnode_sid+0x1f4/0x267
> [<ffffffff81212a19>] ? sel_netnode_find+0xe3/0xe3
> [<ffffffff8120d564>] selinux_socket_bind+0x1cf/0x26f
> [<ffffffff81086c08>] ? lock_release+0x181/0x18e
> [<ffffffff81100db8>] ? might_fault+0xa5/0xac
> [<ffffffff81100d6f>] ? might_fault+0x5c/0xac
> [<ffffffff812073f1>] security_socket_bind+0x16/0x18
> [<ffffffff813ee0e9>] sys_bind+0x73/0xcf
> [<ffffffff814c5d7a>] ? sysret_check+0x2e/0x69
> [<ffffffff810870cf>] ? trace_hardirqs_on_caller+0x10b/0x12f
> [<ffffffff810a9efb>] ? audit_syscall_entry+0x11c/0x148
> [<ffffffff81255e2e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> [<ffffffff814c5d42>] system_call_fastpath+0x16/0x1b
>
>
> something like this perhaps ?
>
> Dave
>
> diff --git a/security/selinux/netnode.c b/security/selinux/netnode.c
> index 65ebfe9..d0c38ba 100644
> --- a/security/selinux/netnode.c
> +++ b/security/selinux/netnode.c
> @@ -188,9 +188,11 @@ static void sel_netnode_insert(struct sel_netnode *node)
> list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
> if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
> struct sel_netnode *tail;
> + rcu_read_lock();
> tail = list_entry(
> rcu_dereference(sel_netnode_hash[idx].list.prev),
> struct sel_netnode, list);
> + rcu_read_unlock();
> list_del_rcu(&tail->list);
> call_rcu(&tail->rcu, sel_netnode_free);
> } else
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: suspicious rcu_dereference_check in security/selinux/netnode.c
2011-04-20 18:42 ` Eric Paris
@ 2011-04-20 19:29 ` Paul Moore
2011-04-21 19:54 ` Paul E. McKenney
0 siblings, 1 reply; 4+ messages in thread
From: Paul Moore @ 2011-04-20 19:29 UTC (permalink / raw)
To: Eric Paris; +Cc: Dave Jones, sds, jmorris, eparis, Linux Kernel, selinux
On Wednesday, April 20, 2011 2:42:04 PM Eric Paris wrote:
> [added paul] EOM
>
> On Wed, 2011-04-20 at 14:35 -0400, Dave Jones wrote:
> > ===================================================
> >
> > [ INFO: suspicious rcu_dereference_check() usage. ]
> > ---------------------------------------------------
> > security/selinux/netnode.c:193 invoked rcu_dereference_check() without
> > protection!
> >
> > other info that might help us debug this:
> >
> > rcu_scheduler_active = 1, debug_locks = 0
> >
> > 1 lock held by a.out/2018:
> > #0: (sel_netnode_lock){+.....}, at: [<ffffffff81212ab7>]
> > sel_netnode_sid+0x9e/0x267
> >
> > stack backtrace:
> > Pid: 2018, comm: a.out Not tainted 2.6.39-rc4+ #3
> >
> > Call Trace:
> > [<ffffffff81084908>] lockdep_rcu_dereference+0xa8/0xb0
> > [<ffffffff81212c0d>] sel_netnode_sid+0x1f4/0x267
> > [<ffffffff81212a19>] ? sel_netnode_find+0xe3/0xe3
> > [<ffffffff8120d564>] selinux_socket_bind+0x1cf/0x26f
> > [<ffffffff81086c08>] ? lock_release+0x181/0x18e
> > [<ffffffff81100db8>] ? might_fault+0xa5/0xac
> > [<ffffffff81100d6f>] ? might_fault+0x5c/0xac
> > [<ffffffff812073f1>] security_socket_bind+0x16/0x18
> > [<ffffffff813ee0e9>] sys_bind+0x73/0xcf
> > [<ffffffff814c5d7a>] ? sysret_check+0x2e/0x69
> > [<ffffffff810870cf>] ? trace_hardirqs_on_caller+0x10b/0x12f
> > [<ffffffff810a9efb>] ? audit_syscall_entry+0x11c/0x148
> > [<ffffffff81255e2e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> > [<ffffffff814c5d42>] system_call_fastpath+0x16/0x1b
> >
> > something like this perhaps ?
> >
> > Dave
> >
> > diff --git a/security/selinux/netnode.c b/security/selinux/netnode.c
> > index 65ebfe9..d0c38ba 100644
> > --- a/security/selinux/netnode.c
> > +++ b/security/selinux/netnode.c
> > @@ -188,9 +188,11 @@ static void sel_netnode_insert(struct sel_netnode
> > *node)
> >
> > list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
> > if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
> >
> > struct sel_netnode *tail;
> >
> > + rcu_read_lock();
> >
> > tail = list_entry(
> >
> > rcu_dereference(sel_netnode_hash[idx].list.prev),
> > struct sel_netnode, list);
> >
> > + rcu_read_unlock();
> >
> > list_del_rcu(&tail->list);
> > call_rcu(&tail->rcu, sel_netnode_free);
> >
> > } else
[Ooops, forgot to hit reply-all on the first attempt]
Hmm, I think the correct fix might be to just remove the rcu_dereference()
call since this is protected by a spin lock (see sel_netnode_sid_slow()). I
may be wrong, but I thought rcu locks/derefs were not needed when a spin lock
was held, yes?
Regardless of the fix, the same thing should probably be done to the
sel_netport_* versions of these functions.
--
paul moore
linux @ hp
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: suspicious rcu_dereference_check in security/selinux/netnode.c
2011-04-20 19:29 ` Paul Moore
@ 2011-04-21 19:54 ` Paul E. McKenney
0 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2011-04-21 19:54 UTC (permalink / raw)
To: Paul Moore
Cc: Eric Paris, Dave Jones, sds, jmorris, eparis, Linux Kernel,
selinux
On Wed, Apr 20, 2011 at 03:29:59PM -0400, Paul Moore wrote:
> On Wednesday, April 20, 2011 2:42:04 PM Eric Paris wrote:
> > [added paul] EOM
> >
> > On Wed, 2011-04-20 at 14:35 -0400, Dave Jones wrote:
> > > ===================================================
> > >
> > > [ INFO: suspicious rcu_dereference_check() usage. ]
> > > ---------------------------------------------------
> > > security/selinux/netnode.c:193 invoked rcu_dereference_check() without
> > > protection!
> > >
> > > other info that might help us debug this:
> > >
> > > rcu_scheduler_active = 1, debug_locks = 0
> > >
> > > 1 lock held by a.out/2018:
> > > #0: (sel_netnode_lock){+.....}, at: [<ffffffff81212ab7>]
> > > sel_netnode_sid+0x9e/0x267
> > >
> > > stack backtrace:
> > > Pid: 2018, comm: a.out Not tainted 2.6.39-rc4+ #3
> > >
> > > Call Trace:
> > > [<ffffffff81084908>] lockdep_rcu_dereference+0xa8/0xb0
> > > [<ffffffff81212c0d>] sel_netnode_sid+0x1f4/0x267
> > > [<ffffffff81212a19>] ? sel_netnode_find+0xe3/0xe3
> > > [<ffffffff8120d564>] selinux_socket_bind+0x1cf/0x26f
> > > [<ffffffff81086c08>] ? lock_release+0x181/0x18e
> > > [<ffffffff81100db8>] ? might_fault+0xa5/0xac
> > > [<ffffffff81100d6f>] ? might_fault+0x5c/0xac
> > > [<ffffffff812073f1>] security_socket_bind+0x16/0x18
> > > [<ffffffff813ee0e9>] sys_bind+0x73/0xcf
> > > [<ffffffff814c5d7a>] ? sysret_check+0x2e/0x69
> > > [<ffffffff810870cf>] ? trace_hardirqs_on_caller+0x10b/0x12f
> > > [<ffffffff810a9efb>] ? audit_syscall_entry+0x11c/0x148
> > > [<ffffffff81255e2e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
> > > [<ffffffff814c5d42>] system_call_fastpath+0x16/0x1b
> > >
> > > something like this perhaps ?
> > >
> > > Dave
> > >
> > > diff --git a/security/selinux/netnode.c b/security/selinux/netnode.c
> > > index 65ebfe9..d0c38ba 100644
> > > --- a/security/selinux/netnode.c
> > > +++ b/security/selinux/netnode.c
> > > @@ -188,9 +188,11 @@ static void sel_netnode_insert(struct sel_netnode
> > > *node)
> > >
> > > list_add_rcu(&node->list, &sel_netnode_hash[idx].list);
> > > if (sel_netnode_hash[idx].size == SEL_NETNODE_HASH_BKT_LIMIT) {
> > >
> > > struct sel_netnode *tail;
> > >
> > > + rcu_read_lock();
> > >
> > > tail = list_entry(
> > >
> > > rcu_dereference(sel_netnode_hash[idx].list.prev),
> > > struct sel_netnode, list);
> > >
> > > + rcu_read_unlock();
> > >
> > > list_del_rcu(&tail->list);
> > > call_rcu(&tail->rcu, sel_netnode_free);
> > >
> > > } else
>
> [Ooops, forgot to hit reply-all on the first attempt]
>
> Hmm, I think the correct fix might be to just remove the rcu_dereference()
> call since this is protected by a spin lock (see sel_netnode_sid_slow()). I
> may be wrong, but I thought rcu locks/derefs were not needed when a spin lock
> was held, yes?
>
> Regardless of the fix, the same thing should probably be done to the
> sel_netport_* versions of these functions.
The lock is sel_netnode_lock, correct? Then the best approach is as
follows:
tail = list_entry(
rcu_dereference_protected(sel_netnode_hash[idx].list.prev,
lockdep_is_held(&sel_netnode_lock)),
struct sel_netnode, list);
Give or take long lines, anyway... :-(
This way, if someone mistakenly calls this function without holding
the lock, CONFIG_PROVE_RCU will know to complain.
And Paul Moore is quite correct when he says that rcu_read_lock() is
not needed in this case.
Thanx, Paul
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2011-04-22 5:59 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2011-04-20 18:35 suspicious rcu_dereference_check in security/selinux/netnode.c Dave Jones
2011-04-20 18:42 ` Eric Paris
2011-04-20 19:29 ` Paul Moore
2011-04-21 19:54 ` Paul E. McKenney
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