// SPDX-License-Identifier: GPL-2.0+
/*
* Originally from efivars.c
*
* Copyright (C) 2001,2003,2004 Dell <[email protected]>
* Copyright (C) 2004 Intel Corporation <[email protected]>
*/
#include <linux/capability.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/smp.h>
#include <linux/efi.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/ucs2_string.h>
#include "internal.h"
MODULE_IMPORT_NS(EFIVAR);
static bool
validate_device_path(efi_char16_t *var_name, int match, u8 *buffer,
unsigned long len)
{
struct efi_generic_dev_path *node;
int offset = 0;
node = (struct efi_generic_dev_path *)buffer;
if (len < sizeof(*node))
return false;
while (offset <= len - sizeof(*node) &&
node->length >= sizeof(*node) &&
node->length <= len - offset) {
offset += node->length;
if ((node->type == EFI_DEV_END_PATH ||
node->type == EFI_DEV_END_PATH2) &&
node->sub_type == EFI_DEV_END_ENTIRE)
return true;
node = (struct efi_generic_dev_path *)(buffer + offset);
}
/*
* If we're here then either node->length pointed past the end
* of the buffer or we reached the end of the buffer without
* finding a device path end node.
*/
return false;
}
static bool
validate_boot_order(efi_char16_t *var_name, int match, u8 *buffer,
unsigned long len)
{
/* An array of 16-bit integers */
if ((len % 2) != 0)
return false;
return true;
}
static bool
validate_load_option(efi_char16_t *var_name, int match, u8 *buffer,
unsigned long len)
{
u16 filepathlength;
int i, desclength = 0, namelen;
namelen = ucs2_strnlen(var_name, EFI_VAR_NAME_LEN);
/* Either "Boot" or "Driver" followed by four digits of hex */
for (i = match; i < match+4; i++) {
if (var_name[i] > 127 ||
hex_to_bin(var_name[i] & 0xff) < 0)
return true;
}
/* Reject it if there's 4 digits of hex and then further content */
if (namelen > match + 4)
return false;
/* A valid entry must be at least 8 bytes */
if (len < 8)
return false;
filepathlength = buffer[4] | buffer[5] << 8;
/*
* There's no stored length for the description, so it has to be
* found by hand
*/
desclength = ucs2_strsize((efi_char16_t *)(buffer + 6), len - 6) + 2;
/* Each boot entry must have a descriptor */
if (!desclength)
return false;
/*
* If the sum of the length of the description, the claimed filepath
* length and the original header are greater than the length of the
* variable, it's malformed
*/
if ((desclength + filepathlength + 6) > len)
return false;
/*
* And, finally, check the filepath
*/
return validate_device_path(var_name, match, buffer + desclength + 6,
filepathlength);
}
static bool
validate_uint16(efi_char16_t *var_name, int match, u8 *buffer,
unsigned long len)
{
/* A single 16-bit integer */
if (len != 2)
return false;
return true;
}
static bool
validate_ascii_string(efi_char16_t *var_name, int match, u8 *buffer,
unsigned long len)
{
int i;
for (i = 0; i < len; i++) {
if (buffer[i] > 127)
return false;
if (buffer[i] == 0)
return true;
}
return false;
}
struct variable_validate {
efi_guid_t vendor;
char *name;
bool (*validate)(efi_char16_t *var_name, int match, u8 *data,
unsigned long len);
};
/*
* This is the list of variables we need to validate, as well as the
* whitelist for what we think is safe not to default to immutable.
*
* If it has a validate() method that's not NULL, it'll go into the
* validation routine. If not, it is assumed valid, but still used for
* whitelisting.
*
* Note that it's sorted by {vendor,name}, but globbed names must come after
* any other name with the same prefix.
*/
static const struct variable_validate variable_validate[] = {
{ EFI_GLOBAL_VARIABLE_GUID, "BootNext", validate_uint16 },
{ EFI_GLOBAL_VARIABLE_GUID, "BootOrder", validate_boot_order },
{ EFI_GLOBAL_VARIABLE_GUID, "Boot*", validate_load_option },
{ EFI_GLOBAL_VARIABLE_GUID, "DriverOrder", validate_boot_order },
{ EFI_GLOBAL_VARIABLE_GUID, "Driver*", validate_load_option },
{ EFI_GLOBAL_VARIABLE_GUID, "ConIn", validate_device_path },
{ EFI_GLOBAL_VARIABLE_GUID, "ConInDev", validate_device_path },
{ EFI_GLOBAL_VARIABLE_GUID, "ConOut", validate_device_path },
{ EFI_GLOBAL_VARIABLE_GUID, "ConOutDev", validate_device_path },
{ EFI_GLOBAL_VARIABLE_GUID, "ErrOut", validate_device_path },
{ EFI_GLOBAL_VARIABLE_GUID, "ErrOutDev", validate_device_path },
{ EFI_GLOBAL_VARIABLE_GUID, "Lang", validate_ascii_string },
{ EFI_GLOBAL_VARIABLE_GUID, "OsIndications", NULL },
{ EFI_GLOBAL_VARIABLE_GUID, "PlatformLang", validate_ascii_string },
{ EFI_GLOBAL_VARIABLE_GUID, "Timeout", validate_uint16 },
{ LINUX_EFI_CRASH_GUID, "*", NULL },
{ NULL_GUID, "", NULL },
};
/*
* Check if @var_name matches the pattern given in @match_name.
*
* @var_name: an array of @len non-NUL characters.
* @match_name: a NUL-terminated pattern string, optionally ending in "*". A
* final "*" character matches any trailing characters @var_name,
* including the case when there are none left in @var_name.
* @match: on output, the number of non-wildcard characters in @match_name
* that @var_name matches, regardless of the return value.
* @return: whether @var_name fully matches @match_name.
*/
static bool
variable_matches(const char *var_name, size_t len, const char *match_name,
int *match)
{
for (*match = 0; ; (*match)++) {
char c = match_name[*match];
switch (c) {
case '*':
/* Wildcard in @match_name means we've matched. */
return true;
case '\0':
/* @match_name has ended. Has @var_name too? */
return (*match == len);
default:
/*
* We've reached a non-wildcard char in @match_name.
* Continue only if there's an identical character in
* @var_name.
*/
if (*match < len && c == var_name[*match])
continue;
return false;
}
}
}
bool
efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
unsigned long data_size)
{
int i;
unsigned long utf8_size;
u8 *utf8_name;
utf8_size = ucs2_utf8size(var_name);
utf8_name = kmalloc(utf8_size + 1, GFP_KERNEL);
if (!utf8_name)
return false;
ucs2_as_utf8(utf8_name, var_name, utf8_size);
utf8_name[utf8_size] = '\0';
for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
const char *name = variable_validate[i].name;
int match = 0;
if (efi_guidcmp(vendor, variable_validate[i].vendor))
continue;
if (variable_matches(utf8_name, utf8_size+1, name, &match)) {
if (variable_validate[i].validate == NULL)
break;
kfree(utf8_name);
return variable_validate[i].validate(var_name, match,
data, data_size);
}
}
kfree(utf8_name);
return true;
}
bool
efivar_variable_is_removable(efi_guid_t vendor, const char *var_name,
size_t len)
{
int i;
bool found = false;
int match = 0;
/*
* Check if our variable is in the validated variables list
*/
for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
if (efi_guidcmp(variable_validate[i].vendor, vendor))
continue;
if (variable_matches(var_name, len,
variable_validate[i].name, &match)) {
found = true;
break;
}
}
/*
* If it's in our list, it is removable.
*/
return found;
}
static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor,
struct list_head *head)
{
struct efivar_entry *entry, *n;
unsigned long strsize1, strsize2;
bool found = false;
strsize1 = ucs2_strsize(variable_name, EFI_VAR_NAME_LEN);
list_for_each_entry_safe(entry, n, head, list) {
strsize2 = ucs2_strsize(entry->var.VariableName, EFI_VAR_NAME_LEN);
if (strsize1 == strsize2 &&
!memcmp(variable_name, &(entry->var.VariableName),
strsize2) &&
!efi_guidcmp(entry->var.VendorGuid,
*vendor)) {
found = true;
break;
}
}
return found;
}
/*
* Returns the size of variable_name, in bytes, including the
* terminating NULL character, or variable_name_size if no NULL
* character is found among the first variable_name_size bytes.
*/
static unsigned long var_name_strnsize(efi_char16_t *variable_name,
unsigned long variable_name_size)
{
unsigned long len;
efi_char16_t c;
/*
* The variable name is, by definition, a NULL-terminated
* string, so make absolutely sure that variable_name_size is
* the value we expect it to be. If not, return the real size.
*/
for (len = 2; len <= variable_name_size; len += sizeof(c)) {
c = variable_name[(len / sizeof(c)) - 1];
if (!c)
break;
}
return min(len, variable_name_size);
}
/*
* Print a warning when duplicate EFI variables are encountered and
* disable the sysfs workqueue since the firmware is buggy.
*/
static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
unsigned long len16)
{
size_t i, len8 = len16 / sizeof(efi_char16_t);
char *str8;
str8 = kzalloc(len8, GFP_KERNEL);
if (!str8)
return;
for (i = 0; i < len8; i++)
str8[i] = str16[i];
printk(KERN_WARNING "efivars: duplicate variable: %s-%pUl\n",
str8, vendor_guid);
kfree(str8);
}
/**
* efivar_init - build the initial list of EFI variables
* @func: callback function to invoke for every variable
* @data: function-specific data to pass to @func
* @head: initialised head of variable list
*
* Get every EFI variable from the firmware and invoke @func. @func
* should call efivar_entry_add() to build the list of variables.
*
* Returns 0 on success, or a kernel error code on failure.
*/
int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *,
struct list_head *),
void *data, struct list_head *head)
{
unsigned long variable_name_size = 512;
efi_char16_t *variable_name;
efi_status_t status;
efi_guid_t vendor_guid;
int err = 0;
variable_name = kzalloc(variable_name_size, GFP_KERNEL);
if (!variable_name) {
printk(KERN_ERR "efivars: Memory allocation failed.\n");
return -ENOMEM;
}
err = efivar_lock();
if (err)
goto free;
/*
* A small set of old UEFI implementations reject sizes
* above a certain threshold, the lowest seen in the wild
* is 512.
*/
do {
variable_name_size = 512;
BUILD_BUG_ON(EFI_VAR_NAME_LEN < 512);
status = efivar_get_next_variable(&variable_name_size,
variable_name,
&vendor_guid);
switch (status) {
case EFI_SUCCESS:
variable_name_size = var_name_strnsize(variable_name,
variable_name_size);
/*
* Some firmware implementations return the
* same variable name on multiple calls to
* get_next_variable(). Terminate the loop
* immediately as there is no guarantee that
* we'll ever see a different variable name,
* and may end up looping here forever.
*/
if (variable_is_present(variable_name, &vendor_guid,
head)) {
dup_variable_bug(variable_name, &vendor_guid,
variable_name_size);
status = EFI_NOT_FOUND;
} else {
err = func(variable_name, vendor_guid,
variable_name_size, data, head);
if (err)
status = EFI_NOT_FOUND;
}
break;
case EFI_UNSUPPORTED:
err = -EOPNOTSUPP;
status = EFI_NOT_FOUND;
break;
case EFI_NOT_FOUND:
break;
case EFI_BUFFER_TOO_SMALL:
pr_warn("efivars: Variable name size exceeds maximum (%lu > 512)\n",
variable_name_size);
status = EFI_NOT_FOUND;
break;
default:
pr_warn("efivars: get_next_variable: status=%lx\n", status);
status = EFI_NOT_FOUND;
break;
}
} while (status != EFI_NOT_FOUND);
efivar_unlock();
free:
kfree(variable_name);
return err;
}
/**
* efivar_entry_add - add entry to variable list
* @entry: entry to add to list
* @head: list head
*
* Returns 0 on success, or a kernel error code on failure.
*/
int efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
{
int err;
err = efivar_lock();
if (err)
return err;
list_add(&entry->list, head);
efivar_unlock();
return 0;
}
/**
* __efivar_entry_add - add entry to variable list
* @entry: entry to add to list
* @head: list head
*/
void __efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
{
list_add(&entry->list, head);
}
/**
* efivar_entry_remove - remove entry from variable list
* @entry: entry to remove from list
*
* Returns 0 on success, or a kernel error code on failure.
*/
void efivar_entry_remove(struct efivar_entry *entry)
{
list_del(&entry->list);
}
/*
* efivar_entry_list_del_unlock - remove entry from variable list
* @entry: entry to remove
*
* Remove @entry from the variable list and release the list lock.
*
* NOTE: slightly weird locking semantics here - we expect to be
* called with the efivars lock already held, and we release it before
* returning. This is because this function is usually called after
* set_variable() while the lock is still held.
*/
static void efivar_entry_list_del_unlock(struct efivar_entry *entry)
{
list_del(&entry->list);
efivar_unlock();
}
/**
* efivar_entry_delete - delete variable and remove entry from list
* @entry: entry containing variable to delete
*
* Delete the variable from the firmware and remove @entry from the
* variable list. It is the caller's responsibility to free @entry
* once we return.
*
* Returns 0 on success, -EINTR if we can't grab the semaphore,
* converted EFI status code if set_variable() fails.
*/
int efivar_entry_delete(struct efivar_entry *entry)
{
efi_status_t status;
int err;
err = efivar_lock();
if (err)
return err;
status = efivar_set_variable_locked(entry->var.VariableName,
&entry->var.VendorGuid,
0, 0, NULL, false);
if (!(status == EFI_SUCCESS || status == EFI_NOT_FOUND)) {
efivar_unlock();
return efi_status_to_err(status);
}
efivar_entry_list_del_unlock(entry);
return 0;
}
/**
* efivar_entry_size - obtain the size of a variable
* @entry: entry for this variable
* @size: location to store the variable's size
*/
int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
{
efi_status_t status;
int err;
*size = 0;
err = efivar_lock();
if (err)
return err;
status = efivar_get_variable(entry->var.VariableName,
&entry->var.VendorGuid, NULL, size, NULL);
efivar_unlock();
if (status != EFI_BUFFER_TOO_SMALL)
return efi_status_to_err(status);
return 0;
}
/**
* __efivar_entry_get - call get_variable()
* @entry: read data for this variable
* @attributes: variable attributes
* @size: size of @data buffer
* @data: buffer to store variable data
*
* The caller MUST call efivar_entry_iter_begin() and
* efivar_entry_iter_end() before and after the invocation of this
* function, respectively.
*/
int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
unsigned long *size, void *data)
{
efi_status_t status;
status = efivar_get_variable(entry->var.VariableName,
&entry->var.VendorGuid,
attributes, size, data);
return efi_status_to_err(status);
}
/**
* efivar_entry_get - call get_variable()
* @entry: read data for this variable
* @attributes: variable attributes
* @size: size of @data buffer
* @data: buffer to store variable data
*/
int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
unsigned long *size, void *data)
{
int err;
err = efivar_lock();
if (err)
return err;
err = __efivar_entry_get(entry, attributes, size, data);
efivar_unlock();
return 0;
}
/**
* efivar_entry_set_get_size - call set_variable() and get new size (atomic)
* @entry: entry containing variable to set and get
* @attributes: attributes of variable to be written
* @size: size of data buffer
* @data: buffer containing data to write
* @set: did the set_variable() call succeed?
*
* This is a pretty special (complex) function. See efivarfs_file_write().
*
* Atomically call set_variable() for @entry and if the call is
* successful, return the new size of the variable from get_variable()
* in @size. The success of set_variable() is indicated by @set.
*
* Returns 0 on success, -EINVAL if the variable data is invalid,
* -ENOSPC if the firmware does not have enough available space, or a
* converted EFI status code if either of set_variable() or
* get_variable() fail.
*
* If the EFI variable does not exist when calling set_variable()
* (EFI_NOT_FOUND), @entry is removed from the variable list.
*/
int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
unsigned long *size, void *data, bool *set)
{
efi_char16_t *name = entry->var.VariableName;
efi_guid_t *vendor = &entry->var.VendorGuid;
efi_status_t status;
int err;
*set = false;
if (efivar_validate(*vendor, name, data, *size) == false)
return -EINVAL;
/*
* The lock here protects the get_variable call, the conditional
* set_variable call, and removal of the variable from the efivars
* list (in the case of an authenticated delete).
*/
err = efivar_lock();
if (err)
return err;
status = efivar_set_variable_locked(name, vendor, attributes, *size,
data, false);
if (status != EFI_SUCCESS) {
err = efi_status_to_err(status);
goto out;
}
*set = true;
/*
* Writing to the variable may have caused a change in size (which
* could either be an append or an overwrite), or the variable to be
* deleted. Perform a GetVariable() so we can tell what actually
* happened.
*/
*size = 0;
status = efivar_get_variable(entry->var.VariableName,
&entry->var.VendorGuid,
NULL, size, NULL);
if (status == EFI_NOT_FOUND)
efivar_entry_list_del_unlock(entry);
else
efivar_unlock();
if (status && status != EFI_BUFFER_TOO_SMALL)
return efi_status_to_err(status);
return 0;
out:
efivar_unlock();
return err;
}
/**
* efivar_entry_iter - iterate over variable list
* @func: callback function
* @head: head of variable list
* @data: function-specific data to pass to callback
*
* Iterate over the list of EFI variables and call @func with every
* entry on the list. It is safe for @func to remove entries in the
* list via efivar_entry_delete() while iterating.
*
* Some notes for the callback function:
* - a non-zero return value indicates an error and terminates the loop
* - @func is called from atomic context
*/
int efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
struct list_head *head, void *data)
{
struct efivar_entry *entry, *n;
int err = 0;
err = efivar_lock();
if (err)
return err;
list_for_each_entry_safe(entry, n, head, list) {
err = func(entry, data);
if (err)
break;
}
efivar_unlock();
return err;
}
Codebase Browser
linux