Commit 2895a5e5 authored Jun 08, 2016 by Eric Caruso Committed by Thomas Gleixner Jun 09, 2016

timerfd: Reject ALARM timerfds without CAP_WAKE_ALARM

timerfd gives processes a way to set wake alarms, but unlike timers made using
timer_create, timerfds don't check whether the process has CAP_WAKE_ALARM
before setting alarm-time timers. CAP_WAKE_ALARM is supposed to gate this
behavior and so it makes sense that we should deny permission to create such
timerfds if the process doesn't have this capability.

Signed-off-by: Eric Caruso <ejcaruso@google.com>
Cc: Todd Poynor <toddpoynor@google.com>
Link: http://lkml.kernel.org/r/1465427339-96209-1-git-send-email-ejcaruso@chromium.org

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent af8c34ce

fs/timerfd.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -390,6 +390,11 @@ SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
		clockid != CLOCK_BOOTTIME_ALARM))
		return -EINVAL;

		if (!capable(CAP_WAKE_ALARM) &&
		(clockid == CLOCK_REALTIME_ALARM \|\|
		clockid == CLOCK_BOOTTIME_ALARM))
		return -EPERM;

		ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
		if (!ctx)
		return -ENOMEM;
		@@ -433,6 +438,11 @@ static int do_timerfd_settime(int ufd, int flags,
		return ret;
		ctx = f.file->private_data;

		if (!capable(CAP_WAKE_ALARM) && isalarm(ctx)) {
		fdput(f);
		return -EPERM;
		}

		timerfd_setup_cancel(ctx, flags);

		/*