sched: Disallow sched_attr::sched_policy < 0

The scheduler uses policy=-1 to preserve the current policy state to
implement sys_sched_setparam(), this got exposed to userspace by
accident through sys_sched_setattr(), cure this.

Reported-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: <stable@vger.kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140509085311.GJ30445@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f2205f02eb70..cdefcf7c5925 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3662,6 +3662,9 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
         if (retval)
                 return retval;
 
+        if (attr.sched_policy < 0)
+                return -EINVAL;
+
         rcu_read_lock();
         retval = -ESRCH;
         p = find_process_by_pid(pid);