watchdog: diag288_wdt: do not use stack buffers for hardware data

commit fe8973a upstream.

With CONFIG_VMAP_STACK=y the stack is allocated from the vmalloc space.
Data passed to a hardware or a hypervisor interface that
requires V=R can no longer be allocated on the stack.

Use kmalloc() to get memory for a diag288 command.

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/watchdog/diag288_wdt.c

@@ -268,12 +268,21 @@ static int __init diag288_init(void)
 	char ebc_begin[] = {
 		194, 197, 199, 201, 213
 	};
+	char *ebc_cmd;
 
 	watchdog_set_nowayout(&wdt_dev, nowayout_info);
 
 	if (MACHINE_IS_VM) {
-		if (__diag288_vm(WDT_FUNC_INIT, 15,
-				 ebc_begin, sizeof(ebc_begin)) != 0) {
+		ebc_cmd = kmalloc(sizeof(ebc_begin), GFP_KERNEL);
+		if (!ebc_cmd) {
+			pr_err("The watchdog cannot be initialized\n");
+			return -ENOMEM;
+		}
+		memcpy(ebc_cmd, ebc_begin, sizeof(ebc_begin));
+		ret = __diag288_vm(WDT_FUNC_INIT, 15,
+				   ebc_cmd, sizeof(ebc_begin));
+		kfree(ebc_cmd);
+		if (ret != 0) {
 			pr_err("The watchdog cannot be initialized\n");
 			return -EINVAL;
 		}