From cc27650286075053b720294b5e23a40b4ffc101c Mon Sep 17 00:00:00 2001
Message-Id: <cc27650286075053b720294b5e23a40b4ffc101c.1599166691.git.zanussi@kernel.org>
In-Reply-To: <56457dc415803c8abc5acb513ada877a79596f05.1599166690.git.zanussi@kernel.org>
References: <56457dc415803c8abc5acb513ada877a79596f05.1599166690.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 11 Oct 2017 17:43:49 +0200
Subject: [PATCH 257/333] apparmor: use a locallock instead preempt_disable()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.142-rt63.tar.xz

get_buffers() disables preemption which acts as a lock for the per-CPU
variable. Since we can't disable preemption here on RT, a local_lock is
lock is used in order to remain on the same CPU and not to have more
than one user within the critical section.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 security/apparmor/include/path.h | 19 ++++++++++++++++---
 security/apparmor/lsm.c          |  2 +-
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/security/apparmor/include/path.h b/security/apparmor/include/path.h
index b6380c5f0097..12abfddb19c9 100644
--- a/security/apparmor/include/path.h
+++ b/security/apparmor/include/path.h
@@ -40,8 +40,10 @@ struct aa_buffers {
 
 #include <linux/percpu.h>
 #include <linux/preempt.h>
+#include <linux/locallock.h>
 
 DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
+DECLARE_LOCAL_IRQ_LOCK(aa_buffers_lock);
 
 #define ASSIGN(FN, A, X, N) ((X) = FN(A, N))
 #define EVAL1(FN, A, X) ASSIGN(FN, A, X, 0) /*X = FN(0)*/
@@ -51,7 +53,17 @@ DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
 
 #define for_each_cpu_buffer(I) for ((I) = 0; (I) < MAX_PATH_BUFFERS; (I)++)
 
-#ifdef CONFIG_DEBUG_PREEMPT
+#ifdef CONFIG_PREEMPT_RT_BASE
+static inline void AA_BUG_PREEMPT_ENABLED(const char *s)
+{
+	struct local_irq_lock *lv;
+
+	lv = this_cpu_ptr(&aa_buffers_lock);
+	WARN_ONCE(lv->owner != current,
+		  "__get_buffer without aa_buffers_lock\n");
+}
+
+#elif defined(CONFIG_DEBUG_PREEMPT)
 #define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
 #else
 #define AA_BUG_PREEMPT_ENABLED(X) /* nop */
@@ -67,14 +79,15 @@ DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
 
 #define get_buffers(X...)						\
 do {									\
-	struct aa_buffers *__cpu_var = get_cpu_ptr(&aa_buffers);	\
+	struct aa_buffers *__cpu_var;					\
+	__cpu_var = get_locked_ptr(aa_buffers_lock, &aa_buffers);	\
 	__get_buffers(__cpu_var, X);					\
 } while (0)
 
 #define put_buffers(X, Y...)		\
 do {					\
 	__put_buffers(X, Y);		\
-	put_cpu_ptr(&aa_buffers);	\
+	put_locked_ptr(aa_buffers_lock, &aa_buffers);	\
 } while (0)
 
 #endif /* __AA_PATH_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 898752b818dc..690c8fccd0a0 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -45,7 +45,7 @@
 int apparmor_initialized;
 
 DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
-
+DEFINE_LOCAL_IRQ_LOCK(aa_buffers_lock);
 
 /*
  * LSM hook functions
-- 
2.17.1

