itimers: Move compat itimer syscalls to native ones

get rid of set_fs(), sanitize compat copyin/copyout.

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/20170607084241.28657-12-viro@ZenIV.linux.org.uk

include/linux/compat.h

@@ -94,6 +94,10 @@ struct compat_itimerval {
 	struct compat_timeval	it_value;
 };
 
+struct itimerval;
+int get_compat_itimerval(struct itimerval *, const struct compat_itimerval __user *);
+int put_compat_itimerval(struct compat_itimerval __user *, const struct itimerval *);
+
 struct compat_tms {
 	compat_clock_t		tms_utime;
 	compat_clock_t		tms_stime;

kernel/compat.c

@@ -217,67 +217,30 @@ int compat_convert_timespec(struct timespec __user **kts,
 	return 0;
 }
 
-static inline long get_compat_itimerval(struct itimerval *o,
-		struct compat_itimerval __user *i)
+int get_compat_itimerval(struct itimerval *o, const struct compat_itimerval __user *i)
 {
-	return (!access_ok(VERIFY_READ, i, sizeof(*i)) ||
-		(__get_user(o->it_interval.tv_sec, &i->it_interval.tv_sec) |
-		 __get_user(o->it_interval.tv_usec, &i->it_interval.tv_usec) |
-		 __get_user(o->it_value.tv_sec, &i->it_value.tv_sec) |
-		 __get_user(o->it_value.tv_usec, &i->it_value.tv_usec)));
-}
+	struct compat_itimerval v32;
 
-static inline long put_compat_itimerval(struct compat_itimerval __user *o,
-		struct itimerval *i)
-{
-	return (!access_ok(VERIFY_WRITE, o, sizeof(*o)) ||
-		(__put_user(i->it_interval.tv_sec, &o->it_interval.tv_sec) |
-		 __put_user(i->it_interval.tv_usec, &o->it_interval.tv_usec) |
-		 __put_user(i->it_value.tv_sec, &o->it_value.tv_sec) |
-		 __put_user(i->it_value.tv_usec, &o->it_value.tv_usec)));
-}
-
-asmlinkage long sys_ni_posix_timers(void);
-
-COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
-		struct compat_itimerval __user *, it)
-{
-	struct itimerval kit;
-	int error;
-
-	if (!IS_ENABLED(CONFIG_POSIX_TIMERS))
-		return sys_ni_posix_timers();
-
-	error = do_getitimer(which, &kit);
-	if (!error && put_compat_itimerval(it, &kit))
-		error = -EFAULT;
-	return error;
-}
-
-COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
-		struct compat_itimerval __user *, in,
-		struct compat_itimerval __user *, out)
-{
-	struct itimerval kin, kout;
-	int error;
-
-	if (!IS_ENABLED(CONFIG_POSIX_TIMERS))
-		return sys_ni_posix_timers();
-
-	if (in) {
-		if (get_compat_itimerval(&kin, in))
-			return -EFAULT;
-	} else
-		memset(&kin, 0, sizeof(kin));
-
-	error = do_setitimer(which, &kin, out ? &kout : NULL);
-	if (error || !out)
-		return error;
-	if (put_compat_itimerval(out, &kout))
+	if (copy_from_user(&v32, i, sizeof(struct compat_itimerval)))
 		return -EFAULT;
+	o->it_interval.tv_sec = v32.it_interval.tv_sec;
+	o->it_interval.tv_usec = v32.it_interval.tv_usec;
+	o->it_value.tv_sec = v32.it_value.tv_sec;
+	o->it_value.tv_usec = v32.it_value.tv_usec;
 	return 0;
 }
 
+int put_compat_itimerval(struct compat_itimerval __user *o, const struct itimerval *i)
+{
+	struct compat_itimerval v32;
+
+	v32.it_interval.tv_sec = i->it_interval.tv_sec;
+	v32.it_interval.tv_usec = i->it_interval.tv_usec;
+	v32.it_value.tv_sec = i->it_value.tv_sec;
+	v32.it_value.tv_usec = i->it_value.tv_usec;
+	return copy_to_user(o, &v32, sizeof(struct compat_itimerval)) ? -EFAULT : 0;
+}
+
 static compat_clock_t clock_t_to_compat_clock_t(clock_t x)
 {
 	return compat_jiffies_to_clock_t(clock_t_to_jiffies(x));

kernel/time/itimer.c

@@ -15,6 +15,7 @@
 #include <linux/posix-timers.h>
 #include <linux/hrtimer.h>
 #include <trace/events/timer.h>
+#include <linux/compat.h>
 
 #include <linux/uaccess.h>
 
@@ -116,6 +117,19 @@ SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
 	return error;
 }
 
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE2(getitimer, int, which,
+		       struct compat_itimerval __user *, it)
+{
+	struct itimerval kit;
+	int error = do_getitimer(which, &kit);
+
+	if (!error && put_compat_itimerval(it, &kit))
+		error = -EFAULT;
+	return error;
+}
+#endif
+
 
 /*
  * The timer is automagically restarted, when interval != 0
@@ -294,3 +308,27 @@ SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 		return -EFAULT;
 	return 0;
 }
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE3(setitimer, int, which,
+		       struct compat_itimerval __user *, in,
+		       struct compat_itimerval __user *, out)
+{
+	struct itimerval kin, kout;
+	int error;
+
+	if (in) {
+		if (get_compat_itimerval(&kin, in))
+			return -EFAULT;
+	} else {
+		memset(&kin, 0, sizeof(kin));
+	}
+
+	error = do_setitimer(which, &kin, out ? &kout : NULL);
+	if (error || !out)
+		return error;
+	if (put_compat_itimerval(out, &kout))
+		return -EFAULT;
+	return 0;
+}
+#endif

kernel/time/posix-stubs.c

@@ -44,6 +44,8 @@ SYS_NI(alarm);
 COMPAT_SYS_NI(clock_adjtime);
 COMPAT_SYS_NI(timer_settime);
 COMPAT_SYS_NI(timer_gettime);
+COMPAT_SYS_NI(getitimer);
+COMPAT_SYS_NI(setitimer);
 
 /*
  * We preserve minimal support for CLOCK_REALTIME and CLOCK_MONOTONIC