linux-kernel - [PATCH 1/2] security/apparmor: Replace homebrew use of write_can

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Message-Id: <1507041166-10618-1-git-send-email-will.deacon@arm.com>
Date:   Tue,  3 Oct 2017 15:32:45 +0100
From:   Will Deacon <will.deacon@....com>
To:     linux-kernel@...r.kernel.org
Cc:     john.johansen@...onical.com, paulmck@...ux.vnet.ibm.com,
        Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 1/2] security/apparmor: Replace homebrew use of write_can_lock with lockdep

The lockdep subsystem provides a robust way to assert that a lock is
held, so use that instead of write_can_lock, which can give incorrect
results for qrwlocks.

Cc: John Johansen <john.johansen@...onical.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Will Deacon <will.deacon@....com>
---
 security/apparmor/include/lib.h | 11 -----------
 security/apparmor/label.c       |  8 ++++----
 2 files changed, 4 insertions(+), 15 deletions(-)

diff --git a/security/apparmor/include/lib.h b/security/apparmor/include/lib.h
index 436b3a722357..f546707a2bbb 100644
--- a/security/apparmor/include/lib.h
+++ b/security/apparmor/include/lib.h
@@ -19,17 +19,6 @@
 
 #include "match.h"
 
-/* Provide our own test for whether a write lock is held for asserts
- * this is because on none SMP systems write_can_lock will always
- * resolve to true, which is what you want for code making decisions
- * based on it, but wrong for asserts checking that the lock is held
- */
-#ifdef CONFIG_SMP
-#define write_is_locked(X) !write_can_lock(X)
-#else
-#define write_is_locked(X) (1)
-#endif /* CONFIG_SMP */
-
 /*
  * DEBUG remains global (no per profile flag) since it is mostly used in sysctl
  * which is not related to profile accesses.
diff --git a/security/apparmor/label.c b/security/apparmor/label.c
index c5b99b954580..ad28e03a6f30 100644
--- a/security/apparmor/label.c
+++ b/security/apparmor/label.c
@@ -80,7 +80,7 @@ void __aa_proxy_redirect(struct aa_label *orig, struct aa_label *new)
 
 	AA_BUG(!orig);
 	AA_BUG(!new);
-	AA_BUG(!write_is_locked(&labels_set(orig)->lock));
+	lockdep_assert_held_exclusive(&labels_set(orig)->lock);
 
 	tmp = rcu_dereference_protected(orig->proxy->label,
 					&labels_ns(orig)->lock);
@@ -571,7 +571,7 @@ static bool __label_remove(struct aa_label *label, struct aa_label *new)
 
 	AA_BUG(!ls);
 	AA_BUG(!label);
-	AA_BUG(!write_is_locked(&ls->lock));
+	lockdep_assert_held_exclusive(&ls->lock);
 
 	if (new)
 		__aa_proxy_redirect(label, new);
@@ -608,7 +608,7 @@ static bool __label_replace(struct aa_label *old, struct aa_label *new)
 	AA_BUG(!ls);
 	AA_BUG(!old);
 	AA_BUG(!new);
-	AA_BUG(!write_is_locked(&ls->lock));
+	lockdep_assert_held_exclusive(&ls->lock);
 	AA_BUG(new->flags & FLAG_IN_TREE);
 
 	if (!label_is_stale(old))
@@ -645,7 +645,7 @@ static struct aa_label *__label_insert(struct aa_labelset *ls,
 	AA_BUG(!ls);
 	AA_BUG(!label);
 	AA_BUG(labels_set(label) != ls);
-	AA_BUG(!write_is_locked(&ls->lock));
+	lockdep_assert_held_exclusive(&ls->lock);
 	AA_BUG(label->flags & FLAG_IN_TREE);
 
 	/* Figure out where to put new node */
-- 
2.1.4