1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
// SPDX-License-Identifier: GPL-2.0-only
/*
* Intel Memory Protection Keys management
* Copyright (c) 2015, Intel Corporation.
*/
#include <linux/debugfs.h> /* debugfs_create_u32() */
#include <linux/mm_types.h> /* mm_struct, vma, etc... */
#include <linux/pkeys.h> /* PKEY_* */
#include <uapi/asm-generic/mman-common.h>
#include <asm/cpufeature.h> /* boot_cpu_has, ... */
#include <asm/mmu_context.h> /* vma_pkey() */
#include <asm/fpu/internal.h> /* init_fpstate */
int __execute_only_pkey(struct mm_struct *mm)
{
bool need_to_set_mm_pkey = false;
int execute_only_pkey = mm->context.execute_only_pkey;
int ret;
/* Do we need to assign a pkey for mm's execute-only maps? */
if (execute_only_pkey == -1) {
/* Go allocate one to use, which might fail */
execute_only_pkey = mm_pkey_alloc(mm);
if (execute_only_pkey < 0)
return -1;
need_to_set_mm_pkey = true;
}
/*
* We do not want to go through the relatively costly
* dance to set PKRU if we do not need to. Check it
* first and assume that if the execute-only pkey is
* write-disabled that we do not have to set it
* ourselves.
*/
if (!need_to_set_mm_pkey &&
!__pkru_allows_read(read_pkru(), execute_only_pkey)) {
return execute_only_pkey;
}
/*
* Set up PKRU so that it denies access for everything
* other than execution.
*/
ret = arch_set_user_pkey_access(current, execute_only_pkey,
PKEY_DISABLE_ACCESS);
/*
* If the PKRU-set operation failed somehow, just return
* 0 and effectively disable execute-only support.
*/
if (ret) {
mm_set_pkey_free(mm, execute_only_pkey);
return -1;
}
/* We got one, store it and use it from here on out */
if (need_to_set_mm_pkey)
mm->context.execute_only_pkey = execute_only_pkey;
return execute_only_pkey;
}
static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
{
/* Do this check first since the vm_flags should be hot */
if ((vma->vm_flags & VM_ACCESS_FLAGS) != VM_EXEC)
return false;
if (vma_pkey(vma) != vma->vm_mm->context.execute_only_pkey)
return false;
return true;
}
/*
* This is only called for *plain* mprotect calls.
*/
int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey)
{
/*
* Is this an mprotect_pkey() call? If so, never
* override the value that came from the user.
*/
if (pkey != -1)
return pkey;
/*
* The mapping is execute-only. Go try to get the
* execute-only protection key. If we fail to do that,
* fall through as if we do not have execute-only
* support in this mm.
*/
if (prot == PROT_EXEC) {
pkey = execute_only_pkey(vma->vm_mm);
if (pkey > 0)
return pkey;
} else if (vma_is_pkey_exec_only(vma)) {
/*
* Protections are *not* PROT_EXEC, but the mapping
* is using the exec-only pkey. This mapping was
* PROT_EXEC and will no longer be. Move back to
* the default pkey.
*/
return ARCH_DEFAULT_PKEY;
}
/*
* This is a vanilla, non-pkey mprotect (or we failed to
* setup execute-only), inherit the pkey from the VMA we
* are working on.
*/
return vma_pkey(vma);
}
#define PKRU_AD_KEY(pkey) (PKRU_AD_BIT << ((pkey) * PKRU_BITS_PER_PKEY))
/*
* Make the default PKRU value (at execve() time) as restrictive
* as possible. This ensures that any threads clone()'d early
* in the process's lifetime will not accidentally get access
* to data which is pkey-protected later on.
*/
u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) |
PKRU_AD_KEY( 4) | PKRU_AD_KEY( 5) | PKRU_AD_KEY( 6) |
PKRU_AD_KEY( 7) | PKRU_AD_KEY( 8) | PKRU_AD_KEY( 9) |
PKRU_AD_KEY(10) | PKRU_AD_KEY(11) | PKRU_AD_KEY(12) |
PKRU_AD_KEY(13) | PKRU_AD_KEY(14) | PKRU_AD_KEY(15);
/*
* Called from the FPU code when creating a fresh set of FPU
* registers. This is called from a very specific context where
* we know the FPU regstiers are safe for use and we can use PKRU
* directly.
*/
void copy_init_pkru_to_fpregs(void)
{
u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value);
/*
* Override the PKRU state that came from 'init_fpstate'
* with the baseline from the process.
*/
write_pkru(init_pkru_value_snapshot);
}
static ssize_t init_pkru_read_file(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{
char buf[32];
unsigned int len;
len = sprintf(buf, "0x%x\n", init_pkru_value);
return simple_read_from_buffer(user_buf, count, ppos, buf, len);
}
static ssize_t init_pkru_write_file(struct file *file,
const char __user *user_buf, size_t count, loff_t *ppos)
{
struct pkru_state *pk;
char buf[32];
ssize_t len;
u32 new_init_pkru;
len = min(count, sizeof(buf) - 1);
if (copy_from_user(buf, user_buf, len))
return -EFAULT;
/* Make the buffer a valid string that we can not overrun */
buf[len] = '\0';
if (kstrtouint(buf, 0, &new_init_pkru))
return -EINVAL;
/*
* Don't allow insane settings that will blow the system
* up immediately if someone attempts to disable access
* or writes to pkey 0.
*/
if (new_init_pkru & (PKRU_AD_BIT|PKRU_WD_BIT))
return -EINVAL;
WRITE_ONCE(init_pkru_value, new_init_pkru);
pk = get_xsave_addr(&init_fpstate.xsave, XFEATURE_PKRU);
if (!pk)
return -EINVAL;
pk->pkru = new_init_pkru;
return count;
}
static const struct file_operations fops_init_pkru = {
.read = init_pkru_read_file,
.write = init_pkru_write_file,
.llseek = default_llseek,
};
static int __init create_init_pkru_value(void)
{
debugfs_create_file("init_pkru", S_IRUSR | S_IWUSR,
arch_debugfs_dir, NULL, &fops_init_pkru);
return 0;
}
late_initcall(create_init_pkru_value);
static __init int setup_init_pkru(char *opt)
{
u32 new_init_pkru;
if (kstrtouint(opt, 0, &new_init_pkru))
return 1;
WRITE_ONCE(init_pkru_value, new_init_pkru);
return 1;
}
__setup("init_pkru=", setup_init_pkru);
|
