[tip: sched/core] sched: Always clear user_cpus_ptr in do_set_cpus_allowed()

[tip-bot2 for Waiman Long]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     851a723e45d1c4c8f6f7b0d2cfbc5f53690bb4e9
Gitweb:        https://git.kernel.org/tip/851a723e45d1c4c8f6f7b0d2cfbc5f53690bb4e9
Author:        Waiman Long <longman@xxxxxxxxxx>
AuthorDate:    Thu, 22 Sep 2022 14:00:41 -04:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 27 Oct 2022 11:01:22 +02:00

sched: Always clear user_cpus_ptr in do_set_cpus_allowed()

The do_set_cpus_allowed() function is used by either kthread_bind() or
select_fallback_rq(). In both cases the user affinity (if any) should be
destroyed too.

Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20220922180041.1768141-6-longman@xxxxxxxxxx
---
 kernel/sched/core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 283bdbd..87c9cdf 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2593,14 +2593,20 @@ __do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx)
 		set_next_task(rq, p);
 }
 
+/*
+ * Used for kthread_bind() and select_fallback_rq(), in both cases the user
+ * affinity (if any) should be destroyed too.
+ */
 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
 {
 	struct affinity_context ac = {
 		.new_mask  = new_mask,
-		.flags     = 0,
+		.user_mask = NULL,
+		.flags     = SCA_USER,	/* clear the user requested mask */
 	};
 
 	__do_set_cpus_allowed(p, &ac);
+	kfree(ac.user_mask);
 }
 
 int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,