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timerfd: Reject ALARM timerfds without CAP_WAKE_ALARM

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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>
This commit is contained in:
Eric Caruso 2016-06-08 16:08:59 -07:00 committed by Thomas Gleixner
parent af8c34ce6a
commit 2895a5e5b3
1 changed files with 10 additions and 0 deletions
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10
fs/timerfd.c
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@ -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);
/*