[tip:sched/core] sched: Use rq->rd in sched_setaffinity() under RCU read lock

[tip-bot for Kirill Tkhai <tipbot@zytor.com>]

Commit-ID:  f1e3a0932f3a9554371792a7daaf1e0eb19f66d5
Gitweb:     http://git.kernel.org/tip/f1e3a0932f3a9554371792a7daaf1e0eb19f66d5
Author:     Kirill Tkhai <ktkhai@parallels.com>
AuthorDate: Mon, 22 Sep 2014 22:36:36 +0400
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Sep 2014 14:47:11 +0200

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>
---
 kernel/sched/core.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 316127a..b5349fe 100644
--- 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: