[PATCH 5/7] sched: Use rq->rd in sched_setaffinity() under RCU read lock

From: Kirill Tkhai
Date: Sat Sep 20 2014 - 12:51:50 EST


From: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>

task_rq(p)->rd and task_rq(p)->rd->span may be used-after-free here.
Probability of NULL pointer derefference isn't zero in this place.

Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v3.14+
---
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 65655a887..a40d6e1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4015,13 +4015,14 @@ 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:

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