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 
module_set_memory(const struct module * mod,enum mod_mem_type type,int (* set_memory)(unsigned long start,int num_pages))15 static 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  */
module_enable_text_rox(const struct module * mod)33 int 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 
module_enable_rodata_ro(const struct module * mod)51 int 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 
module_enable_rodata_ro_after_init(const struct module * mod)68 int 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 
module_enable_data_nx(const struct module * mod)76 int 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 
module_enforce_rwx_sections(Elf_Ehdr * hdr,Elf_Shdr * sechdrs,char * secstrings,struct module * mod)90 int module_enforce_rwx_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
91 				char *secstrings, struct module *mod)
92 {
93 	const unsigned long shf_wx = SHF_WRITE | SHF_EXECINSTR;
94 	int i;
95 
96 	if (!IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
97 		return 0;
98 
99 	for (i = 0; i < hdr->e_shnum; i++) {
100 		if ((sechdrs[i].sh_flags & shf_wx) == shf_wx) {
101 			pr_err("%s: section %s (index %d) has invalid WRITE|EXEC flags\n",
102 			       mod->name, secstrings + sechdrs[i].sh_name, i);
103 			return -ENOEXEC;
104 		}
105 	}
106 
107 	return 0;
108 }
109