* Andrew Morton <[email protected]> wrote:
> There's a glaring bug in selinux_netlbl_inode_permission() - taking
> lock_sock() inside rcu_read_lock().
Note that the bug is still in -rc3, and is easily triggerable via a
default FC6 bootup. It's fixed by the (slightly modified) patch from
Parag Warudkar below that i have in the -rt tree.
Note that this bug became visible due to the recent __resched_legal()
fix, which bug made most of our atomicity debugging checks ineffective.
About half a dozen separate atomicity bugs triggered in -rt when i fixed
the __resched_legal() bug, so i'd expect some more to trigger upstream
too.
Ingo
------------------------>
Subject: [patch] selinux: fix selinux_netlbl_inode_permission() locking
From: Parag Warudkar <[email protected]>
do not call a sleeping lock API in an RCU read section.
lock_sock_nested can sleep, its BH counterpart doesn't.
selinux_netlbl_inode_permission() needs to use the BH counterpart
unconditionally.
Compile tested.
From: Ingo Molnar <[email protected]>
added BH disabling, because this function can be called from non-atomic
contexts too, so a naked bh_lock_sock() would be deadlock-prone.
Boot-tested the resulting kernel.
Signed-off-by: Parag Warudkar <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
---
security/selinux/ss/services.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Index: linux/security/selinux/ss/services.c
===================================================================
--- linux.orig/security/selinux/ss/services.c
+++ linux/security/selinux/ss/services.c
@@ -2660,9 +2660,11 @@ int selinux_netlbl_inode_permission(stru
rcu_read_unlock();
return 0;
}
- lock_sock(sock->sk);
+ local_bh_disable();
+ bh_lock_sock_nested(sock->sk);
rc = selinux_netlbl_socket_setsid(sock, sksec->sid);
- release_sock(sock->sk);
+ bh_unlock_sock(sock->sk);
+ local_bh_enable();
rcu_read_unlock();
return rc;
-
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