mm: reorder can_do_mlock to fix audit denial

A userspace call to mmap(MAP_LOCKED) may result in the successful locking
of memory while also producing a confusing audit log denial.  can_do_mlock
checks capable and rlimit.  If either of these return positive
can_do_mlock returns true.  The capable check leads to an LSM hook used by
apparmour and selinux which produce the audit denial.  Reordering so
rlimit is checked first eliminates the denial on success, only recording a
denial when the lock is unsuccessful as a result of the denial.

Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Acked-by: Nick Kralevich <nnk@google.com>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Paul Cassella <cassella@cray.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mlock.c b/mm/mlock.c
index 33861c7800702df6887ff097982ccfb58837ad10..dd8a0c325a46ea4eed3b4d71e4d6c39ed7a77ade 100644 (file)
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -23,10 +23,10 @@
 
 int can_do_mlock(void)
 {
-       if (capable(CAP_IPC_LOCK))
-               return 1;
        if (rlimit(RLIMIT_MEMLOCK) != 0)
                return 1;
+       if (capable(CAP_IPC_LOCK))
+               return 1;
        return 0;
 }
 EXPORT_SYMBOL(can_do_mlock);