time: Respect COMPAT_32BIT_TIME for old time type functions

The "old" time types use 32-bit seconds which are not y2038-safe.
Respect COMPAT_32BIT_TIME for functions using those types.
time(), stime() and gettimeofday() are disabled completely.

settimeofday() is kept as it is required to do the initial timewarping
after boot. However the 'tv' argument will be rejected.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/lkml/e9487ebe-3730-438a-9c23-e45f75986ecc@app.fastmail.com/
Link: https://patch.msgid.link/20260702-vdso-compat_32bit_time-v3-1-db9f36d8d432@linutronix.de

kernel/sys_ni.c

@@ -351,6 +351,10 @@ COND_SYSCALL(ppoll_time32);
 COND_SYSCALL_COMPAT(ppoll_time32);
 COND_SYSCALL(utimensat_time32);
 COND_SYSCALL(clock_adjtime32);
+COND_SYSCALL(gettimeofday);
+COND_SYSCALL_COMPAT(gettimeofday);
+COND_SYSCALL(time);
+COND_SYSCALL(stime);
 
 /*
  * The syscalls below are not found in include/uapi/asm-generic/unistd.h

kernel/time/time.c

@@ -43,6 +43,12 @@
 #include <generated/timeconst.h>
 #include "timekeeping.h"
 
+#if defined(CONFIG_64BIT) || defined(CONFIG_COMPAT_32BIT_TIME)
+#define __WANT_OLD_TIME_TYPE_SYSCALL 1
+#endif
+
+static_assert(sizeof(__kernel_old_time_t) == 8 ? IS_ENABLED(__WANT_OLD_TIME_TYPE_SYSCALL) : true);
+
 /*
  * The timezone where the local system is located.  Used as a default by some
  * programs who obtain this value by using gettimeofday.
@@ -51,7 +57,7 @@ struct timezone sys_tz;
 
 EXPORT_SYMBOL(sys_tz);
 
-#ifdef __ARCH_WANT_SYS_TIME
+#if defined(__ARCH_WANT_SYS_TIME) && defined(__WANT_OLD_TIME_TYPE_SYSCALL)
 
 /*
  * sys_time() can be implemented in user-level using
@@ -96,7 +102,7 @@ SYSCALL_DEFINE1(stime, __kernel_old_time_t __user *, tptr)
 	return 0;
 }
 
-#endif /* __ARCH_WANT_SYS_TIME */
+#endif /* __ARCH_WANT_SYS_TIME && __WANT_OLD_TIME_TYPE_SYSCALL */
 
 #ifdef CONFIG_COMPAT_32BIT_TIME
 #ifdef __ARCH_WANT_SYS_TIME32
@@ -137,6 +143,7 @@ SYSCALL_DEFINE1(stime32, old_time32_t __user *, tptr)
 #endif /* __ARCH_WANT_SYS_TIME32 */
 #endif
 
+#ifdef __WANT_OLD_TIME_TYPE_SYSCALL
 SYSCALL_DEFINE2(gettimeofday, struct __kernel_old_timeval __user *, tv,
 		struct timezone __user *, tz)
 {
@@ -154,6 +161,7 @@ SYSCALL_DEFINE2(gettimeofday, struct __kernel_old_timeval __user *, tv,
 	}
 	return 0;
 }
+#endif /* __WANT_OLD_TIME_TYPE_SYSCALL */
 
 /*
  * In case for some reason the CMOS clock has not already been running
@@ -203,6 +211,9 @@ SYSCALL_DEFINE2(settimeofday, struct __kernel_old_timeval __user *, tv,
 	struct timezone new_tz;
 
 	if (tv) {
+		if (!IS_ENABLED(__WANT_OLD_TIME_TYPE_SYSCALL))
+			return -EINVAL;
+
 		if (get_user(new_ts.tv_sec, &tv->tv_sec) ||
 		    get_user(new_ts.tv_nsec, &tv->tv_usec))
 			return -EFAULT;
@@ -220,7 +231,7 @@ SYSCALL_DEFINE2(settimeofday, struct __kernel_old_timeval __user *, tv,
 	return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
 }
 
-#ifdef CONFIG_COMPAT
+#ifdef CONFIG_COMPAT_32BIT_TIME
 COMPAT_SYSCALL_DEFINE2(gettimeofday, struct old_timeval32 __user *, tv,
 		       struct timezone __user *, tz)
 {
@@ -239,7 +250,9 @@ COMPAT_SYSCALL_DEFINE2(gettimeofday, struct old_timeval32 __user *, tv,
 
 	return 0;
 }
+#endif /* CONFIG_COMPAT_32BIT_TIME */
 
+#ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
 		       struct timezone __user *, tz)
 {
@@ -247,6 +260,9 @@ COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
 	struct timezone new_tz;
 
 	if (tv) {
+		if (!IS_ENABLED(CONFIG_COMPAT_32BIT_TIME))
+			return -EINVAL;
+
 		if (get_user(new_ts.tv_sec, &tv->tv_sec) ||
 		    get_user(new_ts.tv_nsec, &tv->tv_usec))
 			return -EFAULT;
@@ -263,7 +279,7 @@ COMPAT_SYSCALL_DEFINE2(settimeofday, struct old_timeval32 __user *, tv,
 
 	return do_sys_settimeofday64(tv ? &new_ts : NULL, tz ? &new_tz : NULL);
 }
-#endif
+#endif /* CONFIG_COMPAT */
 
 #ifdef CONFIG_64BIT
 SYSCALL_DEFINE1(adjtimex, struct __kernel_timex __user *, txc_p)