s390/cmm: Replace sprintf() with scnprintf() for buffer safety

Replace sprintf() with scnprintf() in cmm_timeout_handler() to prevent
potential buffer overflow. The scnprintf() function ensures we don't
write beyond the buffer size and provides safer string formatting.

Signed-off-by: Josephine Pfeiffer <hi@josie.lol>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/mm/cmm.c

@@ -321,8 +321,8 @@ static int cmm_timeout_handler(const struct ctl_table *ctl, int write,
 		cmm_set_timeout(nr, seconds);
 		*ppos += *lenp;
 	} else {
-		len = sprintf(buf, "%ld %ld\n",
-			      cmm_timeout_pages, cmm_timeout_seconds);
+		len = scnprintf(buf, sizeof(buf), "%ld %ld\n",
+				cmm_timeout_pages, cmm_timeout_seconds);
 		if (len > *lenp)
 			len = *lenp;
 		memcpy(buffer, buf, len);