xref: /linux/fs/efivarfs/vars.c (revision 136114e0abf03005e182d75761ab694648e6d388)

// SPDX-License-Identifier: GPL-2.0+
/*
 * Originally from efivars.c
 *
 * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
 * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
 */

#include <linux/capability.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/hex.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;
		}
	}
}

char *
efivar_get_utf8name(const efi_char16_t *name16, efi_guid_t *vendor)
{
	int len = ucs2_utf8size(name16);
	char *name;

	/* name, plus '-', plus GUID, plus NUL*/
	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
	if (!name)
		return NULL;

	ucs2_as_utf8(name, name16, len);

	name[len] = '-';

	efi_guid_to_str(vendor, name + len + 1);

	name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';

	/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
	strreplace(name, '/', '!');

	return name;
}

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;
}

/*
 * 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
 * @duplicate_check: fail if a duplicate variable is found
 *
 * Get every EFI variable from the firmware and invoke @func. @func
 * should populate the initial dentry and inode tree.
 *
 * 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 *),
		void *data, bool duplicate_check)
{
	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 (duplicate_check &&
			    efivarfs_variable_is_present(variable_name,
							 &vendor_guid, data)) {
				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);
				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_delete - delete variable
 * @entry: entry containing variable to delete
 *
 * Delete the variable from the firmware. It is the caller's
 * responsibility to free @entry (by deleting the dentry/inode) 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);
	efivar_unlock();
	if (!(status == EFI_SUCCESS || status == EFI_NOT_FOUND))
		return efi_status_to_err(status);

	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 err;
}

/**
 * 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).
 */
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 and the
	 * conditional set_variable call
	 */
	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);

	efivar_unlock();

	if (status && status != EFI_BUFFER_TOO_SMALL)
		return efi_status_to_err(status);

	return 0;

out:
	efivar_unlock();
	return err;

}