From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- drivers/firmware/efi/mokvar-table.c | 362 ++++++++++++++++++++++++++++++++++++ 1 file changed, 362 insertions(+) create mode 100644 drivers/firmware/efi/mokvar-table.c (limited to 'drivers/firmware/efi/mokvar-table.c') diff --git a/drivers/firmware/efi/mokvar-table.c b/drivers/firmware/efi/mokvar-table.c new file mode 100644 index 000000000..5ed0602c2 --- /dev/null +++ b/drivers/firmware/efi/mokvar-table.c @@ -0,0 +1,362 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * mokvar-table.c + * + * Copyright (c) 2020 Red Hat + * Author: Lenny Szubowicz + * + * This module contains the kernel support for the Linux EFI Machine + * Owner Key (MOK) variable configuration table, which is identified by + * the LINUX_EFI_MOK_VARIABLE_TABLE_GUID. + * + * This EFI configuration table provides a more robust alternative to + * EFI volatile variables by which an EFI boot loader can pass the + * contents of the Machine Owner Key (MOK) certificate stores to the + * kernel during boot. If both the EFI MOK config table and corresponding + * EFI MOK variables are present, the table should be considered as + * more authoritative. + * + * This module includes code that validates and maps the EFI MOK table, + * if it's presence was detected very early in boot. + * + * Kernel interface routines are provided to walk through all the + * entries in the MOK config table or to search for a specific named + * entry. + * + * The contents of the individual named MOK config table entries are + * made available to user space via read-only sysfs binary files under: + * + * /sys/firmware/efi/mok-variables/ + * + */ +#define pr_fmt(fmt) "mokvar: " fmt + +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +/* + * The LINUX_EFI_MOK_VARIABLE_TABLE_GUID config table is a packed + * sequence of struct efi_mokvar_table_entry, one for each named + * MOK variable. The sequence is terminated by an entry with a + * completely NULL name and 0 data size. + * + * efi_mokvar_table_size is set to the computed size of the + * MOK config table by efi_mokvar_table_init(). This will be + * non-zero if and only if the table if present and has been + * validated by efi_mokvar_table_init(). + */ +static size_t efi_mokvar_table_size; + +/* + * efi_mokvar_table_va is the kernel virtual address at which the + * EFI MOK config table has been mapped by efi_mokvar_sysfs_init(). + */ +static struct efi_mokvar_table_entry *efi_mokvar_table_va; + +/* + * Each /sys/firmware/efi/mok-variables/ sysfs file is represented by + * an instance of struct efi_mokvar_sysfs_attr on efi_mokvar_sysfs_list. + * bin_attr.private points to the associated EFI MOK config table entry. + * + * This list is created during boot and then remains unchanged. + * So no synchronization is currently required to walk the list. + */ +struct efi_mokvar_sysfs_attr { + struct bin_attribute bin_attr; + struct list_head node; +}; + +static LIST_HEAD(efi_mokvar_sysfs_list); +static struct kobject *mokvar_kobj; + +/* + * efi_mokvar_table_init() - Early boot validation of EFI MOK config table + * + * If present, validate and compute the size of the EFI MOK variable + * configuration table. This table may be provided by an EFI boot loader + * as an alternative to ordinary EFI variables, due to platform-dependent + * limitations. The memory occupied by this table is marked as reserved. + * + * This routine must be called before efi_free_boot_services() in order + * to guarantee that it can mark the table as reserved. + * + * Implicit inputs: + * efi.mokvar_table: Physical address of EFI MOK variable config table + * or special value that indicates no such table. + * + * Implicit outputs: + * efi_mokvar_table_size: Computed size of EFI MOK variable config table. + * The table is considered present and valid if this + * is non-zero. + */ +void __init efi_mokvar_table_init(void) +{ + efi_memory_desc_t md; + void *va = NULL; + unsigned long cur_offset = 0; + unsigned long offset_limit; + unsigned long map_size = 0; + unsigned long map_size_needed = 0; + unsigned long size; + struct efi_mokvar_table_entry *mokvar_entry; + int err; + + if (!efi_enabled(EFI_MEMMAP)) + return; + + if (efi.mokvar_table == EFI_INVALID_TABLE_ADDR) + return; + /* + * The EFI MOK config table must fit within a single EFI memory + * descriptor range. + */ + err = efi_mem_desc_lookup(efi.mokvar_table, &md); + if (err) { + pr_warn("EFI MOKvar config table is not within the EFI memory map\n"); + return; + } + + offset_limit = efi_mem_desc_end(&md) - efi.mokvar_table; + + /* + * Validate the MOK config table. Since there is no table header + * from which we could get the total size of the MOK config table, + * we compute the total size as we validate each variably sized + * entry, remapping as necessary. + */ + err = -EINVAL; + while (cur_offset + sizeof(*mokvar_entry) <= offset_limit) { + mokvar_entry = va + cur_offset; + map_size_needed = cur_offset + sizeof(*mokvar_entry); + if (map_size_needed > map_size) { + if (va) + early_memunmap(va, map_size); + /* + * Map a little more than the fixed size entry + * header, anticipating some data. It's safe to + * do so as long as we stay within current memory + * descriptor. + */ + map_size = min(map_size_needed + 2*EFI_PAGE_SIZE, + offset_limit); + va = early_memremap(efi.mokvar_table, map_size); + if (!va) { + pr_err("Failed to map EFI MOKvar config table pa=0x%lx, size=%lu.\n", + efi.mokvar_table, map_size); + return; + } + mokvar_entry = va + cur_offset; + } + + /* Check for last sentinel entry */ + if (mokvar_entry->name[0] == '\0') { + if (mokvar_entry->data_size != 0) + break; + err = 0; + break; + } + + /* Sanity check that the name is null terminated */ + size = strnlen(mokvar_entry->name, + sizeof(mokvar_entry->name)); + if (size >= sizeof(mokvar_entry->name)) + break; + + /* Advance to the next entry */ + cur_offset = map_size_needed + mokvar_entry->data_size; + } + + if (va) + early_memunmap(va, map_size); + if (err) { + pr_err("EFI MOKvar config table is not valid\n"); + return; + } + + if (md.type == EFI_BOOT_SERVICES_DATA) + efi_mem_reserve(efi.mokvar_table, map_size_needed); + + efi_mokvar_table_size = map_size_needed; +} + +/* + * efi_mokvar_entry_next() - Get next entry in the EFI MOK config table + * + * mokvar_entry: Pointer to current EFI MOK config table entry + * or null. Null indicates get first entry. + * Passed by reference. This is updated to the + * same value as the return value. + * + * Returns: Pointer to next EFI MOK config table entry + * or null, if there are no more entries. + * Same value is returned in the mokvar_entry + * parameter. + * + * This routine depends on the EFI MOK config table being entirely + * mapped with it's starting virtual address in efi_mokvar_table_va. + */ +struct efi_mokvar_table_entry *efi_mokvar_entry_next( + struct efi_mokvar_table_entry **mokvar_entry) +{ + struct efi_mokvar_table_entry *mokvar_cur; + struct efi_mokvar_table_entry *mokvar_next; + size_t size_cur; + + mokvar_cur = *mokvar_entry; + *mokvar_entry = NULL; + + if (efi_mokvar_table_va == NULL) + return NULL; + + if (mokvar_cur == NULL) { + mokvar_next = efi_mokvar_table_va; + } else { + if (mokvar_cur->name[0] == '\0') + return NULL; + size_cur = sizeof(*mokvar_cur) + mokvar_cur->data_size; + mokvar_next = (void *)mokvar_cur + size_cur; + } + + if (mokvar_next->name[0] == '\0') + return NULL; + + *mokvar_entry = mokvar_next; + return mokvar_next; +} + +/* + * efi_mokvar_entry_find() - Find EFI MOK config entry by name + * + * name: Name of the entry to look for. + * + * Returns: Pointer to EFI MOK config table entry if found; + * null otherwise. + * + * This routine depends on the EFI MOK config table being entirely + * mapped with it's starting virtual address in efi_mokvar_table_va. + */ +struct efi_mokvar_table_entry *efi_mokvar_entry_find(const char *name) +{ + struct efi_mokvar_table_entry *mokvar_entry = NULL; + + while (efi_mokvar_entry_next(&mokvar_entry)) { + if (!strncmp(name, mokvar_entry->name, + sizeof(mokvar_entry->name))) + return mokvar_entry; + } + return NULL; +} + +/* + * efi_mokvar_sysfs_read() - sysfs binary file read routine + * + * Returns: Count of bytes read. + * + * Copy EFI MOK config table entry data for this mokvar sysfs binary file + * to the supplied buffer, starting at the specified offset into mokvar table + * entry data, for the specified count bytes. The copy is limited by the + * amount of data in this mokvar config table entry. + */ +static ssize_t efi_mokvar_sysfs_read(struct file *file, struct kobject *kobj, + struct bin_attribute *bin_attr, char *buf, + loff_t off, size_t count) +{ + struct efi_mokvar_table_entry *mokvar_entry = bin_attr->private; + + if (!capable(CAP_SYS_ADMIN)) + return 0; + + if (off >= mokvar_entry->data_size) + return 0; + if (count > mokvar_entry->data_size - off) + count = mokvar_entry->data_size - off; + + memcpy(buf, mokvar_entry->data + off, count); + return count; +} + +/* + * efi_mokvar_sysfs_init() - Map EFI MOK config table and create sysfs + * + * Map the EFI MOK variable config table for run-time use by the kernel + * and create the sysfs entries in /sys/firmware/efi/mok-variables/ + * + * This routine just returns if a valid EFI MOK variable config table + * was not found earlier during boot. + * + * This routine must be called during a "middle" initcall phase, i.e. + * after efi_mokvar_table_init() but before UEFI certs are loaded + * during late init. + * + * Implicit inputs: + * efi.mokvar_table: Physical address of EFI MOK variable config table + * or special value that indicates no such table. + * + * efi_mokvar_table_size: Computed size of EFI MOK variable config table. + * The table is considered present and valid if this + * is non-zero. + * + * Implicit outputs: + * efi_mokvar_table_va: Start virtual address of the EFI MOK config table. + */ +static int __init efi_mokvar_sysfs_init(void) +{ + void *config_va; + struct efi_mokvar_table_entry *mokvar_entry = NULL; + struct efi_mokvar_sysfs_attr *mokvar_sysfs = NULL; + int err = 0; + + if (efi_mokvar_table_size == 0) + return -ENOENT; + + config_va = memremap(efi.mokvar_table, efi_mokvar_table_size, + MEMREMAP_WB); + if (!config_va) { + pr_err("Failed to map EFI MOKvar config table\n"); + return -ENOMEM; + } + efi_mokvar_table_va = config_va; + + mokvar_kobj = kobject_create_and_add("mok-variables", efi_kobj); + if (!mokvar_kobj) { + pr_err("Failed to create EFI mok-variables sysfs entry\n"); + return -ENOMEM; + } + + while (efi_mokvar_entry_next(&mokvar_entry)) { + mokvar_sysfs = kzalloc(sizeof(*mokvar_sysfs), GFP_KERNEL); + if (!mokvar_sysfs) { + err = -ENOMEM; + break; + } + + sysfs_bin_attr_init(&mokvar_sysfs->bin_attr); + mokvar_sysfs->bin_attr.private = mokvar_entry; + mokvar_sysfs->bin_attr.attr.name = mokvar_entry->name; + mokvar_sysfs->bin_attr.attr.mode = 0400; + mokvar_sysfs->bin_attr.size = mokvar_entry->data_size; + mokvar_sysfs->bin_attr.read = efi_mokvar_sysfs_read; + + err = sysfs_create_bin_file(mokvar_kobj, + &mokvar_sysfs->bin_attr); + if (err) + break; + + list_add_tail(&mokvar_sysfs->node, &efi_mokvar_sysfs_list); + } + + if (err) { + pr_err("Failed to create some EFI mok-variables sysfs entries\n"); + kfree(mokvar_sysfs); + } + return err; +} +fs_initcall(efi_mokvar_sysfs_init); -- cgit v1.2.3