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1#include <linux/kernel.h>
2#include <linux/errno.h>
3#include <linux/sched.h>
4#include <linux/user.h>
5#include <linux/regset.h>
6
7#include <asm/uaccess.h>
8#include <asm/desc.h>
9#include <asm/ldt.h>
10#include <asm/processor.h>
11#include <asm/proto.h>
12#include <asm/syscalls.h>
13
14#include "tls.h"
15
16/*
17 * sys_alloc_thread_area: get a yet unused TLS descriptor index.
18 */
19static int get_free_idx(void)
20{
21 struct thread_struct *t = ¤t->thread;
22 int idx;
23
24 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
25 if (desc_empty(&t->tls_array[idx]))
26 return idx + GDT_ENTRY_TLS_MIN;
27 return -ESRCH;
28}
29
30static void set_tls_desc(struct task_struct *p, int idx,
31 const struct user_desc *info, int n)
32{
33 struct thread_struct *t = &p->thread;
34 struct desc_struct *desc = &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
35 int cpu;
36
37 /*
38 * We must not get preempted while modifying the TLS.
39 */
40 cpu = get_cpu();
41
42 while (n-- > 0) {
43 if (LDT_empty(info))
44 desc->a = desc->b = 0;
45 else
46 fill_ldt(desc, info);
47 ++info;
48 ++desc;
49 }
50
51 if (t == ¤t->thread)
52 load_TLS(t, cpu);
53
54 put_cpu();
55}
56
57/*
58 * Set a given TLS descriptor:
59 */
60int do_set_thread_area(struct task_struct *p, int idx,
61 struct user_desc __user *u_info,
62 int can_allocate)
63{
64 struct user_desc info;
65
66 if (copy_from_user(&info, u_info, sizeof(info)))
67 return -EFAULT;
68
69 if (idx == -1)
70 idx = info.entry_number;
71
72 /*
73 * index -1 means the kernel should try to find and
74 * allocate an empty descriptor:
75 */
76 if (idx == -1 && can_allocate) {
77 idx = get_free_idx();
78 if (idx < 0)
79 return idx;
80 if (put_user(idx, &u_info->entry_number))
81 return -EFAULT;
82 }
83
84 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
85 return -EINVAL;
86
87 set_tls_desc(p, idx, &info, 1);
88
89 return 0;
90}
91
92asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
93{
94 int ret = do_set_thread_area(current, -1, u_info, 1);
95 asmlinkage_protect(1, ret, u_info);
96 return ret;
97}
98
99
100/*
101 * Get the current Thread-Local Storage area:
102 */
103
104static void fill_user_desc(struct user_desc *info, int idx,
105 const struct desc_struct *desc)
106
107{
108 memset(info, 0, sizeof(*info));
109 info->entry_number = idx;
110 info->base_addr = get_desc_base(desc);
111 info->limit = get_desc_limit(desc);
112 info->seg_32bit = desc->d;
113 info->contents = desc->type >> 2;
114 info->read_exec_only = !(desc->type & 2);
115 info->limit_in_pages = desc->g;
116 info->seg_not_present = !desc->p;
117 info->useable = desc->avl;
118#ifdef CONFIG_X86_64
119 info->lm = desc->l;
120#endif
121}
122
123int do_get_thread_area(struct task_struct *p, int idx,
124 struct user_desc __user *u_info)
125{
126 struct user_desc info;
127
128 if (idx == -1 && get_user(idx, &u_info->entry_number))
129 return -EFAULT;
130
131 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
132 return -EINVAL;
133
134 fill_user_desc(&info, idx,
135 &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]);
136
137 if (copy_to_user(u_info, &info, sizeof(info)))
138 return -EFAULT;
139 return 0;
140}
141
142asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
143{
144 int ret = do_get_thread_area(current, -1, u_info);
145 asmlinkage_protect(1, ret, u_info);
146 return ret;
147}
148
149int regset_tls_active(struct task_struct *target,
150 const struct user_regset *regset)
151{
152 struct thread_struct *t = &target->thread;
153 int n = GDT_ENTRY_TLS_ENTRIES;
154 while (n > 0 && desc_empty(&t->tls_array[n - 1]))
155 --n;
156 return n;
157}
158
159int regset_tls_get(struct task_struct *target, const struct user_regset *regset,
160 unsigned int pos, unsigned int count,
161 void *kbuf, void __user *ubuf)
162{
163 const struct desc_struct *tls;
164
165 if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
166 (pos % sizeof(struct user_desc)) != 0 ||
167 (count % sizeof(struct user_desc)) != 0)
168 return -EINVAL;
169
170 pos /= sizeof(struct user_desc);
171 count /= sizeof(struct user_desc);
172
173 tls = &target->thread.tls_array[pos];
174
175 if (kbuf) {
176 struct user_desc *info = kbuf;
177 while (count-- > 0)
178 fill_user_desc(info++, GDT_ENTRY_TLS_MIN + pos++,
179 tls++);
180 } else {
181 struct user_desc __user *u_info = ubuf;
182 while (count-- > 0) {
183 struct user_desc info;
184 fill_user_desc(&info, GDT_ENTRY_TLS_MIN + pos++, tls++);
185 if (__copy_to_user(u_info++, &info, sizeof(info)))
186 return -EFAULT;
187 }
188 }
189
190 return 0;
191}
192
193int regset_tls_set(struct task_struct *target, const struct user_regset *regset,
194 unsigned int pos, unsigned int count,
195 const void *kbuf, const void __user *ubuf)
196{
197 struct user_desc infobuf[GDT_ENTRY_TLS_ENTRIES];
198 const struct user_desc *info;
199
200 if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
201 (pos % sizeof(struct user_desc)) != 0 ||
202 (count % sizeof(struct user_desc)) != 0)
203 return -EINVAL;
204
205 if (kbuf)
206 info = kbuf;
207 else if (__copy_from_user(infobuf, ubuf, count))
208 return -EFAULT;
209 else
210 info = infobuf;
211
212 set_tls_desc(target,
213 GDT_ENTRY_TLS_MIN + (pos / sizeof(struct user_desc)),
214 info, count / sizeof(struct user_desc));
215
216 return 0;
217}
1#include <linux/kernel.h>
2#include <linux/errno.h>
3#include <linux/sched.h>
4#include <linux/user.h>
5#include <linux/regset.h>
6#include <linux/syscalls.h>
7
8#include <asm/uaccess.h>
9#include <asm/desc.h>
10#include <asm/ldt.h>
11#include <asm/processor.h>
12#include <asm/proto.h>
13
14#include "tls.h"
15
16/*
17 * sys_alloc_thread_area: get a yet unused TLS descriptor index.
18 */
19static int get_free_idx(void)
20{
21 struct thread_struct *t = ¤t->thread;
22 int idx;
23
24 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
25 if (desc_empty(&t->tls_array[idx]))
26 return idx + GDT_ENTRY_TLS_MIN;
27 return -ESRCH;
28}
29
30static bool tls_desc_okay(const struct user_desc *info)
31{
32 /*
33 * For historical reasons (i.e. no one ever documented how any
34 * of the segmentation APIs work), user programs can and do
35 * assume that a struct user_desc that's all zeros except for
36 * entry_number means "no segment at all". This never actually
37 * worked. In fact, up to Linux 3.19, a struct user_desc like
38 * this would create a 16-bit read-write segment with base and
39 * limit both equal to zero.
40 *
41 * That was close enough to "no segment at all" until we
42 * hardened this function to disallow 16-bit TLS segments. Fix
43 * it up by interpreting these zeroed segments the way that they
44 * were almost certainly intended to be interpreted.
45 *
46 * The correct way to ask for "no segment at all" is to specify
47 * a user_desc that satisfies LDT_empty. To keep everything
48 * working, we accept both.
49 *
50 * Note that there's a similar kludge in modify_ldt -- look at
51 * the distinction between modes 1 and 0x11.
52 */
53 if (LDT_empty(info) || LDT_zero(info))
54 return true;
55
56 /*
57 * espfix is required for 16-bit data segments, but espfix
58 * only works for LDT segments.
59 */
60 if (!info->seg_32bit)
61 return false;
62
63 /* Only allow data segments in the TLS array. */
64 if (info->contents > 1)
65 return false;
66
67 /*
68 * Non-present segments with DPL 3 present an interesting attack
69 * surface. The kernel should handle such segments correctly,
70 * but TLS is very difficult to protect in a sandbox, so prevent
71 * such segments from being created.
72 *
73 * If userspace needs to remove a TLS entry, it can still delete
74 * it outright.
75 */
76 if (info->seg_not_present)
77 return false;
78
79 return true;
80}
81
82static void set_tls_desc(struct task_struct *p, int idx,
83 const struct user_desc *info, int n)
84{
85 struct thread_struct *t = &p->thread;
86 struct desc_struct *desc = &t->tls_array[idx - GDT_ENTRY_TLS_MIN];
87 int cpu;
88
89 /*
90 * We must not get preempted while modifying the TLS.
91 */
92 cpu = get_cpu();
93
94 while (n-- > 0) {
95 if (LDT_empty(info) || LDT_zero(info))
96 desc->a = desc->b = 0;
97 else
98 fill_ldt(desc, info);
99 ++info;
100 ++desc;
101 }
102
103 if (t == ¤t->thread)
104 load_TLS(t, cpu);
105
106 put_cpu();
107}
108
109/*
110 * Set a given TLS descriptor:
111 */
112int do_set_thread_area(struct task_struct *p, int idx,
113 struct user_desc __user *u_info,
114 int can_allocate)
115{
116 struct user_desc info;
117
118 if (copy_from_user(&info, u_info, sizeof(info)))
119 return -EFAULT;
120
121 if (!tls_desc_okay(&info))
122 return -EINVAL;
123
124 if (idx == -1)
125 idx = info.entry_number;
126
127 /*
128 * index -1 means the kernel should try to find and
129 * allocate an empty descriptor:
130 */
131 if (idx == -1 && can_allocate) {
132 idx = get_free_idx();
133 if (idx < 0)
134 return idx;
135 if (put_user(idx, &u_info->entry_number))
136 return -EFAULT;
137 }
138
139 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
140 return -EINVAL;
141
142 set_tls_desc(p, idx, &info, 1);
143
144 return 0;
145}
146
147SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, u_info)
148{
149 return do_set_thread_area(current, -1, u_info, 1);
150}
151
152
153/*
154 * Get the current Thread-Local Storage area:
155 */
156
157static void fill_user_desc(struct user_desc *info, int idx,
158 const struct desc_struct *desc)
159
160{
161 memset(info, 0, sizeof(*info));
162 info->entry_number = idx;
163 info->base_addr = get_desc_base(desc);
164 info->limit = get_desc_limit(desc);
165 info->seg_32bit = desc->d;
166 info->contents = desc->type >> 2;
167 info->read_exec_only = !(desc->type & 2);
168 info->limit_in_pages = desc->g;
169 info->seg_not_present = !desc->p;
170 info->useable = desc->avl;
171#ifdef CONFIG_X86_64
172 info->lm = desc->l;
173#endif
174}
175
176int do_get_thread_area(struct task_struct *p, int idx,
177 struct user_desc __user *u_info)
178{
179 struct user_desc info;
180
181 if (idx == -1 && get_user(idx, &u_info->entry_number))
182 return -EFAULT;
183
184 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
185 return -EINVAL;
186
187 fill_user_desc(&info, idx,
188 &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]);
189
190 if (copy_to_user(u_info, &info, sizeof(info)))
191 return -EFAULT;
192 return 0;
193}
194
195SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, u_info)
196{
197 return do_get_thread_area(current, -1, u_info);
198}
199
200int regset_tls_active(struct task_struct *target,
201 const struct user_regset *regset)
202{
203 struct thread_struct *t = &target->thread;
204 int n = GDT_ENTRY_TLS_ENTRIES;
205 while (n > 0 && desc_empty(&t->tls_array[n - 1]))
206 --n;
207 return n;
208}
209
210int regset_tls_get(struct task_struct *target, const struct user_regset *regset,
211 unsigned int pos, unsigned int count,
212 void *kbuf, void __user *ubuf)
213{
214 const struct desc_struct *tls;
215
216 if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
217 (pos % sizeof(struct user_desc)) != 0 ||
218 (count % sizeof(struct user_desc)) != 0)
219 return -EINVAL;
220
221 pos /= sizeof(struct user_desc);
222 count /= sizeof(struct user_desc);
223
224 tls = &target->thread.tls_array[pos];
225
226 if (kbuf) {
227 struct user_desc *info = kbuf;
228 while (count-- > 0)
229 fill_user_desc(info++, GDT_ENTRY_TLS_MIN + pos++,
230 tls++);
231 } else {
232 struct user_desc __user *u_info = ubuf;
233 while (count-- > 0) {
234 struct user_desc info;
235 fill_user_desc(&info, GDT_ENTRY_TLS_MIN + pos++, tls++);
236 if (__copy_to_user(u_info++, &info, sizeof(info)))
237 return -EFAULT;
238 }
239 }
240
241 return 0;
242}
243
244int regset_tls_set(struct task_struct *target, const struct user_regset *regset,
245 unsigned int pos, unsigned int count,
246 const void *kbuf, const void __user *ubuf)
247{
248 struct user_desc infobuf[GDT_ENTRY_TLS_ENTRIES];
249 const struct user_desc *info;
250 int i;
251
252 if (pos >= GDT_ENTRY_TLS_ENTRIES * sizeof(struct user_desc) ||
253 (pos % sizeof(struct user_desc)) != 0 ||
254 (count % sizeof(struct user_desc)) != 0)
255 return -EINVAL;
256
257 if (kbuf)
258 info = kbuf;
259 else if (__copy_from_user(infobuf, ubuf, count))
260 return -EFAULT;
261 else
262 info = infobuf;
263
264 for (i = 0; i < count / sizeof(struct user_desc); i++)
265 if (!tls_desc_okay(info + i))
266 return -EINVAL;
267
268 set_tls_desc(target,
269 GDT_ENTRY_TLS_MIN + (pos / sizeof(struct user_desc)),
270 info, count / sizeof(struct user_desc));
271
272 return 0;
273}