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
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@xxxxxxxxxxxxx>
---
security/apparmor/include/path.h | 21 +++++++++++++++++----
security/apparmor/lsm.c | 2 +-
2 files changed, 18 insertions(+), 5 deletions(-)
--- a/security/apparmor/include/path.h
+++ b/security/apparmor/include/path.h
@@ -38,9 +38,10 @@ 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 COUNT_ARGS(X...) COUNT_ARGS_HELPER(, ##X, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
#define COUNT_ARGS_HELPER(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, n, X...) n
@@ -54,12 +55,24 @@ DECLARE_PER_CPU(struct aa_buffers, aa_bu
#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 CONFIG_DEBUG_PREEMPT
#define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
#else
#define AA_BUG_PREEMPT_ENABLED(X) /* nop */
#endif
+
#define __get_buffer(N) ({ \
struct aa_buffers *__cpu_var; \
AA_BUG_PREEMPT_ENABLED("__get_buffer without preempt disabled"); \
@@ -72,14 +85,14 @@ DECLARE_PER_CPU(struct aa_buffers, aa_bu
#define get_buffers(X...) \
do { \
- preempt_disable(); \
+ local_lock(aa_buffers_lock); \
__get_buffers(X); \
} while (0)
#define put_buffers(X, Y...) \
do { \
__put_buffers(X, Y); \
- preempt_enable(); \
+ local_unlock(aa_buffers_lock); \
} while (0)
#endif /* __AA_PATH_H */
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -42,7 +42,7 @@
int apparmor_initialized __initdata;
DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
-
+DEFINE_LOCAL_IRQ_LOCK(aa_buffers_lock);
/*
* LSM hook functions
--
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