linux-kernel - [patch 6/6] posix-cpu-timers: Make PID=0 and PID=self handling consistent

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Message-Id: <20190905120540.162032542@linutronix.de>
Date:   Thu, 05 Sep 2019 14:03:45 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Kees Cook <keescook@...omium.org>
Subject: [patch 6/6] posix-cpu-timers: Make PID=0 and PID=self handling
 consistent

If the PID encoded into the clock id is 0 then the target is either the
calling thread itself or the process to which it belongs.

If the current thread encodes its own PID on a process wide clock then
there is no reason not to treat it in the same way as the PID=0 case.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/time/posix-cpu-timers.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -90,7 +90,14 @@ static struct task_struct *lookup_task(c
 
 	} else {
 		/*
-		 * For processes require that p is group leader.
+		 * Timer is going to be attached to a process. If p is
+		 * current then treat it like the PID=0 case above.
+		 */
+		if (p == current)
+			return current->group_leader;
+
+		/*
+		 * For foreign processes require that p is group leader.
 		 */
 		if (!has_group_leader_pid(p))
 			return NULL;