From 2895a5e5b3ae78d9923a91fce405d4a2f32c4309 Mon Sep 17 00:00:00 2001
From: Eric Caruso <ejcaruso@google.com>
Date: Wed, 8 Jun 2016 16:08:59 -0700
Subject: [PATCH] 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>
---
fs/timerfd.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/timerfd.c b/fs/timerfd.c
index 053818dd6c18..9ae4abb4110b 100644
--- a/fs/timerfd.c
+++ b/fs/timerfd.c
@@ -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);
/*