efi: efibc: Guard against allocation failure

There is a single kmalloc in this driver, and it's not currently
guarded against allocation failure. Do it here by just bailing-out
the reboot handler, in case this tentative allocation fails.

Fixes: 416581e ("efi: efibc: avoid efivar API for setting variables")
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/efibc.c

@@ -48,6 +48,9 @@ static int efibc_reboot_notifier_call(struct notifier_block *notifier,
 		return NOTIFY_DONE;
 
 	wdata = kmalloc(MAX_DATA_LEN * sizeof(efi_char16_t), GFP_KERNEL);
+	if (!wdata)
+		return NOTIFY_DONE;
+
 	for (l = 0; l < MAX_DATA_LEN - 1 && str[l] != '\0'; l++)
 		wdata[l] = str[l];
 	wdata[l] = L'\0';