proc: add LSM hook checks to /proc/<tid>/timerslack_ns

As requested, this patch checks the existing LSM hooks
task_getscheduler/task_setscheduler when reading or modifying the task's
timerslack value.

Previous versions added new get/settimerslack LSM hooks, but since they
checked the same PROCESS__SET/GETSCHED values as existing hooks, it was
suggested we just use the existing ones.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: John Stultz <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: "Serge E. Hallyn" <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Arjan van de Ven <[email protected]>
Cc: Oren Laadan <[email protected]>
Cc: Ruchi Kandoi <[email protected]>
Cc: Rom Lemarchand <[email protected]>
Cc: Todd Kjos <[email protected]>
Cc: Colin Cross <[email protected]>
Cc: Nick Kralevich <[email protected]>
Cc: Dmitry Shmidt <[email protected]>
Cc: Elliott Hughes <[email protected]>
Cc: James Morris <[email protected]>
Cc: Android Kernel Team <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 248f008d46b8..ebccdc192830 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2285,6 +2285,12 @@ static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
 		goto out;
 	}
 
+	err = security_task_setscheduler(p);
+	if (err) {
+		count = err;
+		goto out;
+	}
+
 	task_lock(p);
 	if (slack_ns == 0)
 		p->timer_slack_ns = p->default_timer_slack_ns;
@@ -2313,6 +2319,10 @@ static int timerslack_ns_show(struct seq_file *m, void *v)
 		goto out;
 	}
 
+	err = security_task_getscheduler(p);
+	if (err)
+		goto out;
+
 	task_lock(p);
 	seq_printf(m, "%llu\n", p->timer_slack_ns);
 	task_unlock(p);