1// SPDX-License-Identifier: GPL-2.0-or-later
 2/*
 3 * Module strict rwx
 4 *
 5 * Copyright (C) 2015 Rusty Russell
 6 */
 7
 8#include <linux/module.h>
 9#include <linux/mm.h>
10#include <linux/vmalloc.h>
11#include <linux/set_memory.h>
12#include "internal.h"
13
14static void module_set_memory(const struct module *mod, enum mod_mem_type type,
15			      int (*set_memory)(unsigned long start, int num_pages))
16{
17	const struct module_memory *mod_mem = &mod->mem[type];
18
19	set_vm_flush_reset_perms(mod_mem->base);
20	set_memory((unsigned long)mod_mem->base, mod_mem->size >> PAGE_SHIFT);
21}
22
23/*
24 * Since some arches are moving towards PAGE_KERNEL module allocations instead
25 * of PAGE_KERNEL_EXEC, keep module_enable_x() independent of
26 * CONFIG_STRICT_MODULE_RWX because they are needed regardless of whether we
27 * are strict.
28 */
29void module_enable_x(const struct module *mod)
30{
31	for_class_mod_mem_type(type, text)
32		module_set_memory(mod, type, set_memory_x);
33}
34
35void module_enable_ro(const struct module *mod, bool after_init)
36{
37	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
38		return;
39#ifdef CONFIG_STRICT_MODULE_RWX
40	if (!rodata_enabled)
41		return;
42#endif
43
44	module_set_memory(mod, MOD_TEXT, set_memory_ro);
45	module_set_memory(mod, MOD_INIT_TEXT, set_memory_ro);
46	module_set_memory(mod, MOD_RODATA, set_memory_ro);
47	module_set_memory(mod, MOD_INIT_RODATA, set_memory_ro);
48
49	if (after_init)
50		module_set_memory(mod, MOD_RO_AFTER_INIT, set_memory_ro);
51}
52
53void module_enable_nx(const struct module *mod)
54{
55	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
56		return;
57
58	for_class_mod_mem_type(type, data)
59		module_set_memory(mod, type, set_memory_nx);
60}
61
62int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
63				char *secstrings, struct module *mod)
64{
65	const unsigned long shf_wx = SHF_WRITE | SHF_EXECINSTR;
66	int i;
67
68	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
69		return 0;
70
71	for (i = 0; i < hdr->e_shnum; i++) {
72		if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
73			pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
74			       mod->name, secstrings + sechdrs[i].sh_name, i);
75			return -ENOEXEC;
76		}
77	}
78
79	return 0;
80}