kernel core: use helpers for rlimits

Make sure compiler won't do weird things with limits.  E.g.  fetching them
twice may return 2 different values after writable limits are implemented.

I.e.  either use rlimit helpers added in commit 3e10e716abf3 ("resource:
add helpers for fetching rlimits") or ACCESS_ONCE if not applicable.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index dbb16bf15c45..1a22dfd42df9 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -1031,9 +1031,10 @@ static void check_thread_timers(struct task_struct *tsk,
         /*
          * Check for the special case thread timers.
          */
-        soft = sig->rlim[RLIMIT_RTTIME].rlim_cur;
+        soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
         if (soft != RLIM_INFINITY) {
-                unsigned long hard = sig->rlim[RLIMIT_RTTIME].rlim_max;
+                unsigned long hard =
+                        ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
 
                 if (hard != RLIM_INFINITY &&
                     tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
@@ -1194,10 +1195,11 @@ static void check_process_timers(struct task_struct *tsk,
                          SIGPROF);
         check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
                          SIGVTALRM);
-        soft = sig->rlim[RLIMIT_CPU].rlim_cur;
+        soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
         if (soft != RLIM_INFINITY) {
                 unsigned long psecs = cputime_to_secs(ptime);
-                unsigned long hard = sig->rlim[RLIMIT_CPU].rlim_max;
+                unsigned long hard =
+                        ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
                 cputime_t x;
                 if (psecs >= hard) {
                         /*