linux-kernel - [PATCH 1/1] psi: do not require setsched permission from the trigger creator

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Date:   Mon, 29 Jul 2019 18:33:10 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     mingo@...hat.com, peterz@...radead.org
Cc:     lizefan@...wei.com, hannes@...xchg.org, axboe@...nel.dk,
        dennis@...nel.org, dennisszhou@...il.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, Suren Baghdasaryan <surenb@...gle.com>,
        Nick Kralevich <nnk@...gle.com>
Subject: [PATCH 1/1] psi: do not require setsched permission from the trigger creator

When a process creates a new trigger by writing into /proc/pressure/*
files, permissions to write such a file should be used to determine whether
the process is allowed to do so or not. Current implementation would also
require such a process to have setsched capability. Setting of psi trigger
thread's scheduling policy is an implementation detail and should not be
exposed to the user level. Remove the permission check by using _nocheck
version of the function.

Suggested-by: Nick Kralevich <nnk@...gle.com>
Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 kernel/sched/psi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 7acc632c3b82..ed9a1d573cb1 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -1061,7 +1061,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
 			mutex_unlock(&group->trigger_lock);
 			return ERR_CAST(kworker);
 		}
-		sched_setscheduler(kworker->task, SCHED_FIFO, &param);
+		sched_setscheduler_nocheck(kworker->task, SCHED_FIFO, &param);
 		kthread_init_delayed_work(&group->poll_work,
 				psi_poll_work);
 		rcu_assign_pointer(group->poll_kworker, kworker);
-- 
2.22.0.709.g102302147b-goog