linux-kernel - [tip:locking/core] locking/rwsem, security/apparmor: Replace homebrew use of write_can

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Date:   Tue, 10 Oct 2017 04:06:17 -0700
From:   tip-bot for Will Deacon <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, will.deacon@....com, mingo@...nel.org,
        linux-kernel@...r.kernel.org, john.johansen@...onical.com,
        torvalds@...ux-foundation.org, peterz@...radead.org, hpa@...or.com
Subject: [tip:locking/core] locking/rwsem, security/apparmor: Replace
 homebrew use of write_can_lock() with lockdep

Commit-ID:  26c4eb192c6224e5297496cead36404b62fb071b
Gitweb:     https://git.kernel.org/tip/26c4eb192c6224e5297496cead36404b62fb071b
Author:     Will Deacon <will.deacon@....com>
AuthorDate: Tue, 3 Oct 2017 19:25:26 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 10 Oct 2017 11:50:17 +0200

locking/rwsem, 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.

Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: John Johansen <john.johansen@...onical.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: paulmck@...ux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1507055129-12300-1-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 436b3a7..f546707 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 c5b99b9..ad28e03 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 */