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/fork.c b/kernel/fork.c
index bab7b254ad39..b0ec34abc0bb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -828,6 +828,8 @@ void __cleanup_sighand(struct sighand_struct *sighand)
  */
 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 {
+        unsigned long cpu_limit;
+
         /* Thread group counters. */
         thread_group_cputime_init(sig);
 
@@ -842,9 +844,9 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
         sig->cputime_expires.virt_exp = cputime_zero;
         sig->cputime_expires.sched_exp = 0;
 
-        if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
-                sig->cputime_expires.prof_exp =
-                        secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
+        cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
+        if (cpu_limit != RLIM_INFINITY) {
+                sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
                 sig->cputimer.running = 1;
         }
 
@@ -1037,7 +1039,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 #endif
         retval = -EAGAIN;
         if (atomic_read(&p->real_cred->user->processes) >=
-                        p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
+                        task_rlimit(p, RLIMIT_NPROC)) {
                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
                     p->real_cred->user != INIT_USER)
                         goto bad_fork_free;