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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Intel Memory Protection Keys management
4 * Copyright (c) 2015, Intel Corporation.
5 */
6#include <linux/debugfs.h> /* debugfs_create_u32() */
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() */
13#include <asm/fpu/internal.h> /* init_fpstate */
14
15int __execute_only_pkey(struct mm_struct *mm)
16{
17 bool need_to_set_mm_pkey = false;
18 int execute_only_pkey = mm->context.execute_only_pkey;
19 int ret;
20
21 /* Do we need to assign a pkey for mm's execute-only maps? */
22 if (execute_only_pkey == -1) {
23 /* Go allocate one to use, which might fail */
24 execute_only_pkey = mm_pkey_alloc(mm);
25 if (execute_only_pkey < 0)
26 return -1;
27 need_to_set_mm_pkey = true;
28 }
29
30 /*
31 * We do not want to go through the relatively costly
32 * dance to set PKRU if we do not need to. Check it
33 * first and assume that if the execute-only pkey is
34 * write-disabled that we do not have to set it
35 * ourselves.
36 */
37 if (!need_to_set_mm_pkey &&
38 !__pkru_allows_read(read_pkru(), execute_only_pkey)) {
39 return execute_only_pkey;
40 }
41
42 /*
43 * Set up PKRU so that it denies access for everything
44 * other than execution.
45 */
46 ret = arch_set_user_pkey_access(current, execute_only_pkey,
47 PKEY_DISABLE_ACCESS);
48 /*
49 * If the PKRU-set operation failed somehow, just return
50 * 0 and effectively disable execute-only support.
51 */
52 if (ret) {
53 mm_set_pkey_free(mm, execute_only_pkey);
54 return -1;
55 }
56
57 /* We got one, store it and use it from here on out */
58 if (need_to_set_mm_pkey)
59 mm->context.execute_only_pkey = execute_only_pkey;
60 return execute_only_pkey;
61}
62
63static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
64{
65 /* Do this check first since the vm_flags should be hot */
66 if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
67 return false;
68 if (vma_pkey(vma) != vma->vm_mm->context.execute_only_pkey)
69 return false;
70
71 return true;
72}
73
74/*
75 * This is only called for *plain* mprotect calls.
76 */
77int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey)
78{
79 /*
80 * Is this an mprotect_pkey() call? If so, never
81 * override the value that came from the user.
82 */
83 if (pkey != -1)
84 return pkey;
85
86 /*
87 * The mapping is execute-only. Go try to get the
88 * execute-only protection key. If we fail to do that,
89 * fall through as if we do not have execute-only
90 * support in this mm.
91 */
92 if (prot == PROT_EXEC) {
93 pkey = execute_only_pkey(vma->vm_mm);
94 if (pkey > 0)
95 return pkey;
96 } else if (vma_is_pkey_exec_only(vma)) {
97 /*
98 * Protections are *not* PROT_EXEC, but the mapping
99 * is using the exec-only pkey. This mapping was
100 * PROT_EXEC and will no longer be. Move back to
101 * the default pkey.
102 */
103 return ARCH_DEFAULT_PKEY;
104 }
105
106 /*
107 * This is a vanilla, non-pkey mprotect (or we failed to
108 * setup execute-only), inherit the pkey from the VMA we
109 * are working on.
110 */
111 return vma_pkey(vma);
112}
113
114#define PKRU_AD_KEY(pkey) (PKRU_AD_BIT << ((pkey) * PKRU_BITS_PER_PKEY))
115
116/*
117 * Make the default PKRU value (at execve() time) as restrictive
118 * as possible. This ensures that any threads clone()'d early
119 * in the process's lifetime will not accidentally get access
120 * to data which is pkey-protected later on.
121 */
122u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) |
123 PKRU_AD_KEY( 4) | PKRU_AD_KEY( 5) | PKRU_AD_KEY( 6) |
124 PKRU_AD_KEY( 7) | PKRU_AD_KEY( 8) | PKRU_AD_KEY( 9) |
125 PKRU_AD_KEY(10) | PKRU_AD_KEY(11) | PKRU_AD_KEY(12) |
126 PKRU_AD_KEY(13) | PKRU_AD_KEY(14) | PKRU_AD_KEY(15);
127
128/*
129 * Called from the FPU code when creating a fresh set of FPU
130 * registers. This is called from a very specific context where
131 * we know the FPU regstiers are safe for use and we can use PKRU
132 * directly.
133 */
134void copy_init_pkru_to_fpregs(void)
135{
136 u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value);
137 /*
138 * Override the PKRU state that came from 'init_fpstate'
139 * with the baseline from the process.
140 */
141 write_pkru(init_pkru_value_snapshot);
142}
143
144static ssize_t init_pkru_read_file(struct file *file, char __user *user_buf,
145 size_t count, loff_t *ppos)
146{
147 char buf[32];
148 unsigned int len;
149
150 len = sprintf(buf, "0x%x\n", init_pkru_value);
151 return simple_read_from_buffer(user_buf, count, ppos, buf, len);
152}
153
154static ssize_t init_pkru_write_file(struct file *file,
155 const char __user *user_buf, size_t count, loff_t *ppos)
156{
157 struct pkru_state *pk;
158 char buf[32];
159 ssize_t len;
160 u32 new_init_pkru;
161
162 len = min(count, sizeof(buf) - 1);
163 if (copy_from_user(buf, user_buf, len))
164 return -EFAULT;
165
166 /* Make the buffer a valid string that we can not overrun */
167 buf[len] = '\0';
168 if (kstrtouint(buf, 0, &new_init_pkru))
169 return -EINVAL;
170
171 /*
172 * Don't allow insane settings that will blow the system
173 * up immediately if someone attempts to disable access
174 * or writes to pkey 0.
175 */
176 if (new_init_pkru & (PKRU_AD_BIT|PKRU_WD_BIT))
177 return -EINVAL;
178
179 WRITE_ONCE(init_pkru_value, new_init_pkru);
180 pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
181 if (!pk)
182 return -EINVAL;
183 pk->pkru = new_init_pkru;
184 return count;
185}
186
187static const struct file_operations fops_init_pkru = {
188 .read = init_pkru_read_file,
189 .write = init_pkru_write_file,
190 .llseek = default_llseek,
191};
192
193static int __init create_init_pkru_value(void)
194{
195 debugfs_create_file("init_pkru", S_IRUSR | S_IWUSR,
196 arch_debugfs_dir, NULL, &fops_init_pkru);
197 return 0;
198}
199late_initcall(create_init_pkru_value);
200
201static __init int setup_init_pkru(char *opt)
202{
203 u32 new_init_pkru;
204
205 if (kstrtouint(opt, 0, &new_init_pkru))
206 return 1;
207
208 WRITE_ONCE(init_pkru_value, new_init_pkru);
209
210 return 1;
211}
212__setup("init_pkru=", setup_init_pkru);
1/*
2 * Intel Memory Protection Keys management
3 * Copyright (c) 2015, Intel Corporation.
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms and conditions of the GNU General Public License,
7 * version 2, as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
12 * more details.
13 */
14#include <linux/mm_types.h> /* mm_struct, vma, etc... */
15#include <linux/pkeys.h> /* PKEY_* */
16#include <uapi/asm-generic/mman-common.h>
17
18#include <asm/cpufeature.h> /* boot_cpu_has, ... */
19#include <asm/mmu_context.h> /* vma_pkey() */
20#include <asm/fpu/internal.h> /* fpregs_active() */
21
22int __execute_only_pkey(struct mm_struct *mm)
23{
24 int ret;
25
26 /*
27 * We do not want to go through the relatively costly
28 * dance to set PKRU if we do not need to. Check it
29 * first and assume that if the execute-only pkey is
30 * write-disabled that we do not have to set it
31 * ourselves. We need preempt off so that nobody
32 * can make fpregs inactive.
33 */
34 preempt_disable();
35 if (fpregs_active() &&
36 !__pkru_allows_read(read_pkru(), PKEY_DEDICATED_EXECUTE_ONLY)) {
37 preempt_enable();
38 return PKEY_DEDICATED_EXECUTE_ONLY;
39 }
40 preempt_enable();
41 ret = arch_set_user_pkey_access(current, PKEY_DEDICATED_EXECUTE_ONLY,
42 PKEY_DISABLE_ACCESS);
43 /*
44 * If the PKRU-set operation failed somehow, just return
45 * 0 and effectively disable execute-only support.
46 */
47 if (ret)
48 return 0;
49
50 return PKEY_DEDICATED_EXECUTE_ONLY;
51}
52
53static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
54{
55 /* Do this check first since the vm_flags should be hot */
56 if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
57 return false;
58 if (vma_pkey(vma) != PKEY_DEDICATED_EXECUTE_ONLY)
59 return false;
60
61 return true;
62}
63
64/*
65 * This is only called for *plain* mprotect calls.
66 */
67int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey)
68{
69 /*
70 * Is this an mprotect_pkey() call? If so, never
71 * override the value that came from the user.
72 */
73 if (pkey != -1)
74 return pkey;
75 /*
76 * Look for a protection-key-drive execute-only mapping
77 * which is now being given permissions that are not
78 * execute-only. Move it back to the default pkey.
79 */
80 if (vma_is_pkey_exec_only(vma) &&
81 (prot & (PROT_READ|PROT_WRITE))) {
82 return 0;
83 }
84 /*
85 * The mapping is execute-only. Go try to get the
86 * execute-only protection key. If we fail to do that,
87 * fall through as if we do not have execute-only
88 * support.
89 */
90 if (prot == PROT_EXEC) {
91 pkey = execute_only_pkey(vma->vm_mm);
92 if (pkey > 0)
93 return pkey;
94 }
95 /*
96 * This is a vanilla, non-pkey mprotect (or we failed to
97 * setup execute-only), inherit the pkey from the VMA we
98 * are working on.
99 */
100 return vma_pkey(vma);
101}