ntp: Move adjtimex related compat syscalls to native counterparts

Get rid of set_fs() mess and sanitize compat_{get,put}_timex(),
while we are at it.

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/20170607084241.28657-9-viro@ZenIV.linux.org.uk

kernel/time/posix-stubs.c

@@ -28,6 +28,7 @@ asmlinkage long sys_ni_posix_timers(void)
 }
 
 #define SYS_NI(name)  SYSCALL_ALIAS(sys_##name, sys_ni_posix_timers)
+#define COMPAT_SYS_NI(name)  SYSCALL_ALIAS(compat_sys_##name, sys_ni_posix_timers)
 
 SYS_NI(timer_create);
 SYS_NI(timer_gettime);
@@ -40,6 +41,7 @@ SYS_NI(setitimer);
 #ifdef __ARCH_WANT_SYS_ALARM
 SYS_NI(alarm);
 #endif
+COMPAT_SYS_NI(clock_adjtime);
 
 /*
  * We preserve minimal support for CLOCK_REALTIME and CLOCK_MONOTONIC

kernel/time/posix-timers.c

@@ -1018,6 +1018,33 @@ SYSCALL_DEFINE2(clock_adjtime, const clockid_t, which_clock,
 	return err;
 }
 
+#ifdef CONFIG_COMPAT
+
+COMPAT_SYSCALL_DEFINE2(clock_adjtime, clockid_t, which_clock,
+		       struct compat_timex __user *, utp)
+{
+	const struct k_clock *kc = clockid_to_kclock(which_clock);
+	struct timex ktx;
+	int err;
+
+	if (!kc)
+		return -EINVAL;
+	if (!kc->clock_adj)
+		return -EOPNOTSUPP;
+
+	err = compat_get_timex(&ktx, utp);
+	if (err)
+		return err;
+
+	err = kc->clock_adj(which_clock, &ktx);
+
+	if (err >= 0)
+		err = compat_put_timex(utp, &ktx);
+
+	return err;
+}
+#endif
+
 SYSCALL_DEFINE2(clock_getres, const clockid_t, which_clock,
 		struct timespec __user *, tp)
 {

kernel/time/time.c

@@ -39,6 +39,7 @@
 #include <linux/ptrace.h>
 
 #include <linux/uaccess.h>
+#include <linux/compat.h>
 #include <asm/unistd.h>
 
 #include <generated/timeconst.h>
@@ -224,12 +225,33 @@ SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p)
 	 * structure. But bear in mind that the structures
 	 * may change
 	 */
-	if(copy_from_user(&txc, txc_p, sizeof(struct timex)))
+	if (copy_from_user(&txc, txc_p, sizeof(struct timex)))
 		return -EFAULT;
 	ret = do_adjtimex(&txc);
 	return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret;
 }
 
+#ifdef CONFIG_COMPAT
+
+COMPAT_SYSCALL_DEFINE1(adjtimex, struct compat_timex __user *, utp)
+{
+	struct timex txc;
+	int err, ret;
+
+	err = compat_get_timex(&txc, utp);
+	if (err)
+		return err;
+
+	ret = do_adjtimex(&txc);
+
+	err = compat_put_timex(utp, &txc);
+	if (err)
+		return err;
+
+	return ret;
+}
+#endif
+
 /*
  * Convert jiffies to milliseconds and back.
  *