Merge branch 'for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/jlawall...
[linux-2.6-microblaze.git] / arch / x86 / mm / pkeys.c
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
15 int __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
63 static 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_ACCESS_FLAGS) != 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  */
77 int __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  */
122 u32 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  */
134 void 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
144 static 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
154 static 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
187 static 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
193 static 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 }
199 late_initcall(create_init_pkru_value);
200
201 static __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);