From: Sebastian Andrzej Siewior Date: Wed, 11 Oct 2017 17:43:49 +0200 Subject: apparmor: use a locallock instead preempt_disable() Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.16/older/patches-4.16.7-rt1.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 --- 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 @@ -39,9 +39,10 @@ struct aa_buffers { }; #include -#include +#include 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 @@ -55,12 +56,24 @@ 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 defined(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"); \ @@ -73,14 +86,14 @@ 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 @@ -44,7 +44,7 @@ int apparmor_initialized; DEFINE_PER_CPU(struct aa_buffers, aa_buffers); - +DEFINE_LOCAL_IRQ_LOCK(aa_buffers_lock); /* * LSM hook functions