diff --git a/kernel/reboot.c b/kernel/reboot.c
index 4fd4b93b7a61..ac19159d7158 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -558,6 +558,13 @@ static int __init reboot_setup(char *str)
 				reboot_cpu = simple_strtoul(str+3, NULL, 0);
 			else
 				*mode = REBOOT_SOFT;
+			if (reboot_cpu >= num_possible_cpus()) {
+				pr_err("Ignoring the CPU number in reboot= option. "
+				       "CPU %d exceeds possible cpu number %d\n",
+				       reboot_cpu, num_possible_cpus());
+				reboot_cpu = 0;
+				break;
+			}
 			break;
 
 		case 'g':