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2025cf9e | 1 | // SPDX-License-Identifier: GPL-2.0-only |
62b5f7d0 DH |
2 | /* |
3 | * Intel Memory Protection Keys management | |
4 | * Copyright (c) 2015, Intel Corporation. | |
62b5f7d0 | 5 | */ |
76de9937 | 6 | #include <linux/debugfs.h> /* debugfs_create_u32() */ |
62b5f7d0 DH |
7 | #include <linux/mm_types.h> /* mm_struct, vma, etc... */ |
8 | #include <linux/pkeys.h> /* PKEY_* */ | |
9 | #include <uapi/asm-generic/mman-common.h> | |
10 | ||
11 | #include <asm/cpufeature.h> /* boot_cpu_has, ... */ | |
12 | #include <asm/mmu_context.h> /* vma_pkey() */ | |
62b5f7d0 DH |
13 | |
14 | int __execute_only_pkey(struct mm_struct *mm) | |
15 | { | |
e8c24d3a DH |
16 | bool need_to_set_mm_pkey = false; |
17 | int execute_only_pkey = mm->context.execute_only_pkey; | |
62b5f7d0 DH |
18 | int ret; |
19 | ||
e8c24d3a DH |
20 | /* Do we need to assign a pkey for mm's execute-only maps? */ |
21 | if (execute_only_pkey == -1) { | |
22 | /* Go allocate one to use, which might fail */ | |
23 | execute_only_pkey = mm_pkey_alloc(mm); | |
24 | if (execute_only_pkey < 0) | |
25 | return -1; | |
26 | need_to_set_mm_pkey = true; | |
27 | } | |
28 | ||
62b5f7d0 DH |
29 | /* |
30 | * We do not want to go through the relatively costly | |
31 | * dance to set PKRU if we do not need to. Check it | |
32 | * first and assume that if the execute-only pkey is | |
33 | * write-disabled that we do not have to set it | |
2722146e | 34 | * ourselves. |
62b5f7d0 | 35 | */ |
e8c24d3a | 36 | if (!need_to_set_mm_pkey && |
e8c24d3a | 37 | !__pkru_allows_read(read_pkru(), execute_only_pkey)) { |
e8c24d3a | 38 | return execute_only_pkey; |
62b5f7d0 | 39 | } |
e8c24d3a DH |
40 | |
41 | /* | |
42 | * Set up PKRU so that it denies access for everything | |
43 | * other than execution. | |
44 | */ | |
45 | ret = arch_set_user_pkey_access(current, execute_only_pkey, | |
62b5f7d0 DH |
46 | PKEY_DISABLE_ACCESS); |
47 | /* | |
48 | * If the PKRU-set operation failed somehow, just return | |
49 | * 0 and effectively disable execute-only support. | |
50 | */ | |
e8c24d3a DH |
51 | if (ret) { |
52 | mm_set_pkey_free(mm, execute_only_pkey); | |
53 | return -1; | |
54 | } | |
62b5f7d0 | 55 | |
e8c24d3a DH |
56 | /* We got one, store it and use it from here on out */ |
57 | if (need_to_set_mm_pkey) | |
58 | mm->context.execute_only_pkey = execute_only_pkey; | |
59 | return execute_only_pkey; | |
62b5f7d0 DH |
60 | } |
61 | ||
62 | static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma) | |
63 | { | |
64 | /* Do this check first since the vm_flags should be hot */ | |
6cb4d9a2 | 65 | if ((vma->vm_flags & VM_ACCESS_FLAGS) != VM_EXEC) |
62b5f7d0 | 66 | return false; |
e8c24d3a | 67 | if (vma_pkey(vma) != vma->vm_mm->context.execute_only_pkey) |
62b5f7d0 DH |
68 | return false; |
69 | ||
70 | return true; | |
71 | } | |
72 | ||
73 | /* | |
74 | * This is only called for *plain* mprotect calls. | |
75 | */ | |
76 | int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey) | |
77 | { | |
78 | /* | |
79 | * Is this an mprotect_pkey() call? If so, never | |
80 | * override the value that came from the user. | |
81 | */ | |
82 | if (pkey != -1) | |
83 | return pkey; | |
0a0b1520 | 84 | |
62b5f7d0 DH |
85 | /* |
86 | * The mapping is execute-only. Go try to get the | |
87 | * execute-only protection key. If we fail to do that, | |
88 | * fall through as if we do not have execute-only | |
0a0b1520 | 89 | * support in this mm. |
62b5f7d0 DH |
90 | */ |
91 | if (prot == PROT_EXEC) { | |
92 | pkey = execute_only_pkey(vma->vm_mm); | |
93 | if (pkey > 0) | |
94 | return pkey; | |
0a0b1520 DH |
95 | } else if (vma_is_pkey_exec_only(vma)) { |
96 | /* | |
97 | * Protections are *not* PROT_EXEC, but the mapping | |
98 | * is using the exec-only pkey. This mapping was | |
99 | * PROT_EXEC and will no longer be. Move back to | |
100 | * the default pkey. | |
101 | */ | |
102 | return ARCH_DEFAULT_PKEY; | |
62b5f7d0 | 103 | } |
0a0b1520 | 104 | |
62b5f7d0 DH |
105 | /* |
106 | * This is a vanilla, non-pkey mprotect (or we failed to | |
107 | * setup execute-only), inherit the pkey from the VMA we | |
108 | * are working on. | |
109 | */ | |
110 | return vma_pkey(vma); | |
111 | } | |
acd547b2 | 112 | |
54ee1844 | 113 | #define PKRU_AD_MASK(pkey) (PKRU_AD_BIT << ((pkey) * PKRU_BITS_PER_PKEY)) |
acd547b2 DH |
114 | |
115 | /* | |
116 | * Make the default PKRU value (at execve() time) as restrictive | |
117 | * as possible. This ensures that any threads clone()'d early | |
118 | * in the process's lifetime will not accidentally get access | |
119 | * to data which is pkey-protected later on. | |
120 | */ | |
54ee1844 IW |
121 | u32 init_pkru_value = PKRU_AD_MASK( 1) | PKRU_AD_MASK( 2) | |
122 | PKRU_AD_MASK( 3) | PKRU_AD_MASK( 4) | | |
123 | PKRU_AD_MASK( 5) | PKRU_AD_MASK( 6) | | |
124 | PKRU_AD_MASK( 7) | PKRU_AD_MASK( 8) | | |
125 | PKRU_AD_MASK( 9) | PKRU_AD_MASK(10) | | |
126 | PKRU_AD_MASK(11) | PKRU_AD_MASK(12) | | |
127 | PKRU_AD_MASK(13) | PKRU_AD_MASK(14) | | |
128 | PKRU_AD_MASK(15); | |
acd547b2 | 129 | |
76de9937 DH |
130 | static ssize_t init_pkru_read_file(struct file *file, char __user *user_buf, |
131 | size_t count, loff_t *ppos) | |
132 | { | |
133 | char buf[32]; | |
134 | unsigned int len; | |
135 | ||
136 | len = sprintf(buf, "0x%x\n", init_pkru_value); | |
137 | return simple_read_from_buffer(user_buf, count, ppos, buf, len); | |
138 | } | |
139 | ||
140 | static ssize_t init_pkru_write_file(struct file *file, | |
141 | const char __user *user_buf, size_t count, loff_t *ppos) | |
142 | { | |
143 | char buf[32]; | |
144 | ssize_t len; | |
145 | u32 new_init_pkru; | |
146 | ||
147 | len = min(count, sizeof(buf) - 1); | |
148 | if (copy_from_user(buf, user_buf, len)) | |
149 | return -EFAULT; | |
150 | ||
151 | /* Make the buffer a valid string that we can not overrun */ | |
152 | buf[len] = '\0'; | |
153 | if (kstrtouint(buf, 0, &new_init_pkru)) | |
154 | return -EINVAL; | |
155 | ||
156 | /* | |
157 | * Don't allow insane settings that will blow the system | |
158 | * up immediately if someone attempts to disable access | |
159 | * or writes to pkey 0. | |
160 | */ | |
161 | if (new_init_pkru & (PKRU_AD_BIT|PKRU_WD_BIT)) | |
162 | return -EINVAL; | |
163 | ||
164 | WRITE_ONCE(init_pkru_value, new_init_pkru); | |
165 | return count; | |
166 | } | |
167 | ||
168 | static const struct file_operations fops_init_pkru = { | |
169 | .read = init_pkru_read_file, | |
170 | .write = init_pkru_write_file, | |
171 | .llseek = default_llseek, | |
172 | }; | |
173 | ||
174 | static int __init create_init_pkru_value(void) | |
175 | { | |
314a1e1e DH |
176 | /* Do not expose the file if pkeys are not supported. */ |
177 | if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) | |
178 | return 0; | |
179 | ||
76de9937 DH |
180 | debugfs_create_file("init_pkru", S_IRUSR | S_IWUSR, |
181 | arch_debugfs_dir, NULL, &fops_init_pkru); | |
182 | return 0; | |
183 | } | |
184 | late_initcall(create_init_pkru_value); | |
185 | ||
186 | static __init int setup_init_pkru(char *opt) | |
187 | { | |
188 | u32 new_init_pkru; | |
189 | ||
190 | if (kstrtouint(opt, 0, &new_init_pkru)) | |
191 | return 1; | |
192 | ||
193 | WRITE_ONCE(init_pkru_value, new_init_pkru); | |
194 | ||
195 | return 1; | |
196 | } | |
197 | __setup("init_pkru=", setup_init_pkru); |