sched: Use rq->rd in sched_setaffinity() under RCU read lock

Probability of use-after-free isn't zero in this place.

Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # v3.14+
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140922183636.11015.83611.stgit@localhost
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 316127acefc6e735ba34876606ce040db4ad5408..b5349fee1213d5d2df92c2e59353eec6588d6cd1 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4049,13 +4049,14 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
         * root_domain.
         */
 #ifdef CONFIG_SMP
-       if (task_has_dl_policy(p)) {
-               const struct cpumask *span = task_rq(p)->rd->span;
-
-               if (dl_bandwidth_enabled() && !cpumask_subset(span, new_mask)) {
+       if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
+               rcu_read_lock();
+               if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
                        retval = -EBUSY;
+                       rcu_read_unlock();
                        goto out_free_new_mask;
                }
+               rcu_read_unlock();
        }
 #endif
 again: