linux-kernel - [PATCH] psi: allow unprivileged users with CAP_SYS

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Date:   Wed, 31 Mar 2021 23:31:56 -0400
From:   Josh Hunt <johunt@...mai.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        <linux-kernel@...r.kernel.org>
CC:     Josh Hunt <johunt@...mai.com>
Subject: [PATCH] psi: allow unprivileged users with CAP_SYS_RESOURCE to write psi files

Currently only root can write files under /proc/pressure. Relax this to
allow tasks running as unprivileged users with CAP_SYS_RESOURCE to be
able to write to these files.

Signed-off-by: Josh Hunt <johunt@...mai.com>
---
 kernel/sched/psi.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index b1b00e9bd7ed..98ff7baf1ba8 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -1270,6 +1270,9 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf,
 	if (!nbytes)
 		return -EINVAL;
 
+	if (!capable(CAP_SYS_RESOURCE))
+		return -EPERM;
+
 	buf_size = min(nbytes, sizeof(buf));
 	if (copy_from_user(buf, user_buf, buf_size))
 		return -EFAULT;
@@ -1353,9 +1356,9 @@ static int __init psi_proc_init(void)
 {
 	if (psi_enable) {
 		proc_mkdir("pressure", NULL);
-		proc_create("pressure/io", 0, NULL, &psi_io_proc_ops);
-		proc_create("pressure/memory", 0, NULL, &psi_memory_proc_ops);
-		proc_create("pressure/cpu", 0, NULL, &psi_cpu_proc_ops);
+		proc_create("pressure/io", 0666, NULL, &psi_io_proc_ops);
+		proc_create("pressure/memory", 0666, NULL, &psi_memory_proc_ops);
+		proc_create("pressure/cpu", 0666, NULL, &psi_cpu_proc_ops);
 	}
 	return 0;
 }
-- 
2.17.1