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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 <linux/execmem.h>
13#include "internal.h"
14
15static int module_set_memory(const struct module *mod, enum mod_mem_type type,
16 int (*set_memory)(unsigned long start, int num_pages))
17{
18 const struct module_memory *mod_mem = &mod->mem[type];
19
20 if (!mod_mem->base)
21 return 0;
22
23 set_vm_flush_reset_perms(mod_mem->base);
24 return set_memory((unsigned long)mod_mem->base, mod_mem->size >> PAGE_SHIFT);
25}
26
27/*
28 * Since some arches are moving towards PAGE_KERNEL module allocations instead
29 * of PAGE_KERNEL_EXEC, keep module_enable_x() independent of
30 * CONFIG_STRICT_MODULE_RWX because they are needed regardless of whether we
31 * are strict.
32 */
33int module_enable_text_rox(const struct module *mod)
34{
35 for_class_mod_mem_type(type, text) {
36 const struct module_memory *mem = &mod->mem[type];
37 int ret;
38
39 if (mem->is_rox)
40 ret = execmem_restore_rox(mem->base, mem->size);
41 else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
42 ret = module_set_memory(mod, type, set_memory_rox);
43 else
44 ret = module_set_memory(mod, type, set_memory_x);
45 if (ret)
46 return ret;
47 }
48 return 0;
49}
50
51int module_enable_rodata_ro(const struct module *mod)
52{
53 int ret;
54
55 if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX) || !rodata_enabled)
56 return 0;
57
58 ret = module_set_memory(mod, MOD_RODATA, set_memory_ro);
59 if (ret)
60 return ret;
61 ret = module_set_memory(mod, MOD_INIT_RODATA, set_memory_ro);
62 if (ret)
63 return ret;
64
65 return 0;
66}
67
68int module_enable_rodata_ro_after_init(const struct module *mod)
69{
70 if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX) || !rodata_enabled)
71 return 0;
72
73 return module_set_memory(mod, MOD_RO_AFTER_INIT, set_memory_ro);
74}
75
76int module_enable_data_nx(const struct module *mod)
77{
78 if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
79 return 0;
80
81 for_class_mod_mem_type(type, data) {
82 int ret = module_set_memory(mod, type, set_memory_nx);
83
84 if (ret)
85 return ret;
86 }
87 return 0;
88}
89
90int module_enforce_rwx_sections(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
91 const char *secstrings,
92 const struct module *mod)
93{
94 const unsigned long shf_wx = SHF_WRITE | SHF_EXECINSTR;
95 int i;
96
97 if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
98 return 0;
99
100 for (i = 0; i < hdr->e_shnum; i++) {
101 if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
102 pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
103 mod->name, secstrings + sechdrs[i].sh_name, i);
104 return -ENOEXEC;
105 }
106 }
107
108 return 0;
109}
110
111static const char *const ro_after_init[] = {
112 /*
113 * Section .data..ro_after_init holds data explicitly annotated by
114 * __ro_after_init.
115 */
116 ".data..ro_after_init",
117
118 /*
119 * Section __jump_table holds data structures that are never modified,
120 * with the exception of entries that refer to code in the __init
121 * section, which are marked as such at module load time.
122 */
123 "__jump_table",
124
125#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
126 /*
127 * Section .static_call_sites holds data structures that need to be
128 * sorted and processed at module load time but are never modified
129 * afterwards.
130 */
131 ".static_call_sites",
132#endif
133};
134
135void module_mark_ro_after_init(const Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
136 const char *secstrings)
137{
138 int i, j;
139
140 for (i = 1; i < hdr->e_shnum; i++) {
141 Elf_Shdr *shdr = &sechdrs[i];
142
143 for (j = 0; j < ARRAY_SIZE(ro_after_init); j++) {
144 if (strcmp(secstrings + shdr->sh_name,
145 ro_after_init[j]) == 0) {
146 shdr->sh_flags |= SHF_RO_AFTER_INIT;
147 break;
148 }
149 }
150 }
151}