Commit 416581e4 authored by Ard Biesheuvel's avatar Ard Biesheuvel
Browse files

efi: efibc: avoid efivar API for setting variables 



Avoid abusing the efivar API by passing locally instantiated
efivar_entry structs into efivar_set_entry_safe(), rather than using the
API as intended. Instead, just call efi.set_variable() directly.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
parent 3881ee0b

drivers/firmware/efi/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -145,6 +145,7 @@ config EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER 


config EFI_BOOTLOADER_CONTROL

	tristate "EFI Bootloader Control"

	select UCS2_STRING

	default n

	help

	  This module installs a reboot hook, such that if reboot() is

drivers/firmware/efi/efibc.c

+29 −47
Original line number Diff line number Diff line
@@ -10,69 +10,51 @@ 
#include <linux/module.h>

#include <linux/reboot.h>

#include <linux/slab.h>

#include <linux/ucs2_string.h>



static void efibc_str_to_str16(const char *str, efi_char16_t *str16)

{

	size_t i;



	for (i = 0; i < strlen(str); i++)

		str16[i] = str[i];



	str16[i] = '\0';

}

#define MAX_DATA_LEN	512



static int efibc_set_variable(const char *name, const char *value)

static int efibc_set_variable(efi_char16_t *name, efi_char16_t *value,

			      unsigned long len)

{

	int ret;

	efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;

	struct efivar_entry *entry;

	size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);



	if (size > sizeof(entry->var.Data)) {

		pr_err("value is too large (%zu bytes) for '%s' EFI variable\n", size, name);

		return -EINVAL;

	}



	entry = kmalloc(sizeof(*entry), GFP_KERNEL);

	if (!entry) {

		pr_err("failed to allocate efivar entry for '%s' EFI variable\n", name);

		return -ENOMEM;

	}



	efibc_str_to_str16(name, entry->var.VariableName);

	efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);

	memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));

	efi_status_t status;



	ret = efivar_entry_set_safe(entry->var.VariableName,

				    entry->var.VendorGuid,

	status = efi.set_variable(name, &LINUX_EFI_LOADER_ENTRY_GUID,

				  EFI_VARIABLE_NON_VOLATILE

				  | EFI_VARIABLE_BOOTSERVICE_ACCESS

				  | EFI_VARIABLE_RUNTIME_ACCESS,

				    false, size, entry->var.Data);



	if (ret)

		pr_err("failed to set %s EFI variable: 0x%x\n",

		       name, ret);

				  len * sizeof(efi_char16_t), value);



	kfree(entry);

	return ret;

	if (status != EFI_SUCCESS) {

		pr_err("failed to set EFI variable: 0x%lx\n", status);

		return -EIO;

	}

	return 0;

}



static int efibc_reboot_notifier_call(struct notifier_block *notifier,

				      unsigned long event, void *data)

{

	const char *reason = "shutdown";

	efi_char16_t *reason = event == SYS_RESTART ? L"reboot"

						    : L"shutdown";

	const u8 *str = data;

	efi_char16_t *wdata;

	unsigned long l;

	int ret;



	if (event == SYS_RESTART)

		reason = "reboot";



	ret = efibc_set_variable("LoaderEntryRebootReason", reason);

	ret = efibc_set_variable(L"LoaderEntryRebootReason", reason,

				 ucs2_strlen(reason));

	if (ret || !data)

		return NOTIFY_DONE;



	efibc_set_variable("LoaderEntryOneShot", (char *)data);

	wdata = kmalloc(MAX_DATA_LEN * sizeof(efi_char16_t), GFP_KERNEL);

	for (l = 0; l < MAX_DATA_LEN - 1 && str[l] != '\0'; l++)

		wdata[l] = str[l];

	wdata[l] = L'\0';



	efibc_set_variable(L"LoaderEntryOneShot", wdata, l);



	kfree(wdata);

	return NOTIFY_DONE;

}
@@ -84,7 +66,7 @@ static int __init efibc_init(void) 
{

	int ret;



	if (!efivars_kobject() || !efivar_supports_writes())

	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE))

		return -ENODEV;



	ret = register_reboot_notifier(&efibc_reboot_notifier);