ipc: sem: Make sem_array timestamps y2038 safe

time_t is not y2038 safe. Replace all uses of
time_t by y2038 safe time64_t.

Similarly, replace the calls to get_seconds() with
y2038 safe ktime_get_real_seconds().
Note that this preserves fast access on 64 bit systems,
but 32 bit systems need sequence counters.

The syscall interface themselves are not changed as part of
the patch. They will be part of a different series.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/sem.h

@@ -4,6 +4,7 @@
 #include <linux/atomic.h>
 #include <linux/rcupdate.h>
 #include <linux/cache.h>
+#include <linux/time64.h>
 #include <uapi/linux/sem.h>
 
 struct task_struct;
@@ -30,7 +31,7 @@ struct sem {
 /* One sem_array data structure for each set of semaphores in the system. */
 struct sem_array {
 	struct kern_ipc_perm	sem_perm;	/* permissions .. see ipc.h */
-	time_t			sem_ctime;	/* create/last semctl() time */
+	time64_t		sem_ctime;	/* create/last semctl() time */
 	struct list_head	pending_alter;	/* pending operations */
 						/* that alter the array */
 	struct list_head	pending_const;	/* pending complex operations */

ipc/sem.c

@@ -511,7 +511,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 	INIT_LIST_HEAD(&sma->pending_const);
 	INIT_LIST_HEAD(&sma->list_id);
 	sma->sem_nsems = nsems;
-	sma->sem_ctime = get_seconds();
+	sma->sem_ctime = ktime_get_real_seconds();
 
 	retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
 	if (retval < 0) {
@@ -1162,14 +1162,14 @@ static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in,
 	}
 }
 
-static time_t get_semotime(struct sem_array *sma)
+static time64_t get_semotime(struct sem_array *sma)
 {
 	int i;
-	time_t res;
+	time64_t res;
 
 	res = sma->sems[0].sem_otime;
 	for (i = 1; i < sma->sem_nsems; i++) {
-		time_t to = sma->sems[i].sem_otime;
+		time64_t to = sma->sems[i].sem_otime;
 
 		if (to > res)
 			res = to;
@@ -1309,7 +1309,7 @@ static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
 
 	curr->semval = val;
 	curr->sempid = task_tgid_vnr(current);
-	sma->sem_ctime = get_seconds();
+	sma->sem_ctime = ktime_get_real_seconds();
 	/* maybe some queued-up processes were waiting for this */
 	do_smart_update(sma, NULL, 0, 0, &wake_q);
 	sem_unlock(sma, -1);
@@ -1437,7 +1437,7 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 			for (i = 0; i < nsems; i++)
 				un->semadj[i] = 0;
 		}
-		sma->sem_ctime = get_seconds();
+		sma->sem_ctime = ktime_get_real_seconds();
 		/* maybe some queued-up processes were waiting for this */
 		do_smart_update(sma, NULL, 0, 0, &wake_q);
 		err = 0;
@@ -1547,7 +1547,7 @@ static int semctl_down(struct ipc_namespace *ns, int semid,
 		err = ipc_update_perm(&semid64->sem_perm, ipcp);
 		if (err)
 			goto out_unlock0;
-		sma->sem_ctime = get_seconds();
+		sma->sem_ctime = ktime_get_real_seconds();
 		break;
 	default:
 		err = -EINVAL;
@@ -2292,7 +2292,7 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
 {
 	struct user_namespace *user_ns = seq_user_ns(s);
 	struct sem_array *sma = it;
-	time_t sem_otime;
+	time64_t sem_otime;
 
 	/*
 	 * The proc interface isn't aware of sem_lock(), it calls
@@ -2305,7 +2305,7 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
 	sem_otime = get_semotime(sma);
 
 	seq_printf(s,
-		   "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
+		   "%10d %10d  %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
 		   sma->sem_perm.key,
 		   sma->sem_perm.id,
 		   sma->sem_perm.mode,