posix-timers: Take compat timer_settime(2) to native one

... and get rid of set_fs() in there
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170607084241.28657-10-viro@ZenIV.linux.org.uk

kernel/compat.c

@@ -635,29 +635,6 @@ COMPAT_SYSCALL_DEFINE3(timer_create, clockid_t, which_clock,
 	return sys_timer_create(which_clock, event, created_timer_id);
 }
 
-COMPAT_SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
-		       struct compat_itimerspec __user *, new,
-		       struct compat_itimerspec __user *, old)
-{
-	long err;
-	mm_segment_t oldfs;
-	struct itimerspec newts, oldts;
-
-	if (!new)
-		return -EINVAL;
-	if (get_compat_itimerspec(&newts, new))
-		return -EFAULT;
-	oldfs = get_fs();
-	set_fs(KERNEL_DS);
-	err = sys_timer_settime(timer_id, flags,
-				(struct itimerspec __user *) &newts,
-				(struct itimerspec __user *) &oldts);
-	set_fs(oldfs);
-	if (!err && old && put_compat_itimerspec(old, &oldts))
-		return -EFAULT;
-	return err;
-}
-
 COMPAT_SYSCALL_DEFINE2(timer_gettime, timer_t, timer_id,
 		       struct compat_itimerspec __user *, setting)
 {

kernel/time/posix-stubs.c

@@ -42,6 +42,7 @@ SYS_NI(setitimer);
 SYS_NI(alarm);
 #endif
 COMPAT_SYS_NI(clock_adjtime);
+COMPAT_SYS_NI(timer_settime);
 
 /*
  * We preserve minimal support for CLOCK_REALTIME and CLOCK_MONOTONIC

kernel/time/posix-timers.c

@@ -819,31 +819,21 @@ int common_timer_set(struct k_itimer *timr, int flags,
 	return 0;
 }
 
-/* Set a POSIX.1b interval timer */
-SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
-		const struct itimerspec __user *, new_setting,
-		struct itimerspec __user *, old_setting)
+static int do_timer_settime(timer_t timer_id, int flags,
+			    struct itimerspec64 *new_spec64,
+			    struct itimerspec64 *old_spec64)
 {
-	struct itimerspec64 new_spec64, old_spec64;
-	struct itimerspec64 *rtn = old_setting ? &old_spec64 : NULL;
-	struct itimerspec new_spec, old_spec;
+	const struct k_clock *kc;
 	struct k_itimer *timr;
 	unsigned long flag;
-	const struct k_clock *kc;
 	int error = 0;
 
-	if (!new_setting)
+	if (!timespec64_valid(&new_spec64->it_interval) ||
+	    !timespec64_valid(&new_spec64->it_value))
 		return -EINVAL;
 
-	if (copy_from_user(&new_spec, new_setting, sizeof (new_spec)))
-		return -EFAULT;
-	new_spec64 = itimerspec_to_itimerspec64(&new_spec);
-
-	if (!timespec64_valid(&new_spec64.it_interval) ||
-	    !timespec64_valid(&new_spec64.it_value))
-		return -EINVAL;
-	if (rtn)
-		memset(rtn, 0, sizeof(*rtn));
+	if (old_spec64)
+		memset(old_spec64, 0, sizeof(*old_spec64));
 retry:
 	timr = lock_timer(timer_id, &flag);
 	if (!timr)
@@ -853,22 +843,71 @@ SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
 	if (WARN_ON_ONCE(!kc || !kc->timer_set))
 		error = -EINVAL;
 	else
-		error = kc->timer_set(timr, flags, &new_spec64, rtn);
+		error = kc->timer_set(timr, flags, new_spec64, old_spec64);
 
 	unlock_timer(timr, flag);
 	if (error == TIMER_RETRY) {
-		rtn = NULL;	// We already got the old time...
+		old_spec64 = NULL;	// We already got the old time...
 		goto retry;
 	}
 
-	old_spec = itimerspec64_to_itimerspec(&old_spec64);
-	if (old_setting && !error &&
-	    copy_to_user(old_setting, &old_spec, sizeof (old_spec)))
-		error = -EFAULT;
+	return error;
+}
+
+/* Set a POSIX.1b interval timer */
+SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
+		const struct itimerspec __user *, new_setting,
+		struct itimerspec __user *, old_setting)
+{
+	struct itimerspec64 new_spec64, old_spec64;
+	struct itimerspec64 *rtn = old_setting ? &old_spec64 : NULL;
+	struct itimerspec new_spec;
+	int error = 0;
+
+	if (!new_setting)
+		return -EINVAL;
 
+	if (copy_from_user(&new_spec, new_setting, sizeof (new_spec)))
+		return -EFAULT;
+	new_spec64 = itimerspec_to_itimerspec64(&new_spec);
+
+	error = do_timer_settime(timer_id, flags, &new_spec64, rtn);
+	if (!error && old_setting) {
+		struct itimerspec old_spec;
+		old_spec = itimerspec64_to_itimerspec(&old_spec64);
+		if (copy_to_user(old_setting, &old_spec, sizeof (old_spec)))
+			error = -EFAULT;
+	}
 	return error;
 }
 
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE4(timer_settime, timer_t, timer_id, int, flags,
+		       struct compat_itimerspec __user *, new,
+		       struct compat_itimerspec __user *, old)
+{
+	struct itimerspec64 new_spec64, old_spec64;
+	struct itimerspec64 *rtn = old ? &old_spec64 : NULL;
+	struct itimerspec new_spec;
+	int error = 0;
+
+	if (!new)
+		return -EINVAL;
+	if (get_compat_itimerspec(&new_spec, new))
+		return -EFAULT;
+
+	new_spec64 = itimerspec_to_itimerspec64(&new_spec);
+	error = do_timer_settime(timer_id, flags, &new_spec64, rtn);
+	if (!error && old) {
+		struct itimerspec old_spec;
+		old_spec = itimerspec64_to_itimerspec(&old_spec64);
+		if (put_compat_itimerspec(old, &old_spec))
+			error = -EFAULT;
+	}
+	return error;
+}
+#endif
+
 int common_timer_del(struct k_itimer *timer)
 {
 	const struct k_clock *kc = timer->kclock;