[PATCH] psi: allow unprivileged users with CAP_SYS_RESOURCE to write psi files

[Josh Hunt]

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 <joh...@akamai.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