projects/linux·blob v4.0-rc1 · refs

280 lines · 6.0 KiB

1/*
2 * Supplementary group IDs
3 */
4#include <linux/cred.h>
5#include <linux/export.h>
6#include <linux/slab.h>
7#include <linux/security.h>
8#include <linux/syscalls.h>
9#include <linux/user_namespace.h>
10#include <asm/uaccess.h>
11
12/* init to 2 - one for init_task, one to ensure it is never freed */
13struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
14
15struct group_info *groups_alloc(int gidsetsize)
16{
17 struct group_info *group_info;
18 int nblocks;
19 int i;
20
21 nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;
22 /* Make sure we always allocate at least one indirect block pointer */
23 nblocks = nblocks ? : 1;
24 group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER);
25 if (!group_info)
26 return NULL;
27 group_info->ngroups = gidsetsize;
28 group_info->nblocks = nblocks;
29 atomic_set(&group_info->usage, 1);
30
31 if (gidsetsize <= NGROUPS_SMALL)
32 group_info->blocks[0] = group_info->small_block;
33 else {
34 for (i = 0; i < nblocks; i++) {
35 kgid_t *b;
36 b = (void *)__get_free_page(GFP_USER);
37 if (!b)
38 goto out_undo_partial_alloc;
39 group_info->blocks[i] = b;
40 }
41 }
42 return group_info;
43
44out_undo_partial_alloc:
45 while (--i >= 0) {
46 free_page((unsigned long)group_info->blocks[i]);
47 }
48 kfree(group_info);
49 return NULL;
50}
51
52EXPORT_SYMBOL(groups_alloc);
53
54void groups_free(struct group_info *group_info)
55{
56 if (group_info->blocks[0] != group_info->small_block) {
57 int i;
58 for (i = 0; i < group_info->nblocks; i++)
59 free_page((unsigned long)group_info->blocks[i]);
60 }
61 kfree(group_info);
62}
63
64EXPORT_SYMBOL(groups_free);
65
66/* export the group_info to a user-space array */
67static int groups_to_user(gid_t __user *grouplist,
68 const struct group_info *group_info)
69{
70 struct user_namespace *user_ns = current_user_ns();
71 int i;
72 unsigned int count = group_info->ngroups;
73
74 for (i = 0; i < count; i++) {
75 gid_t gid;
76 gid = from_kgid_munged(user_ns, GROUP_AT(group_info, i));
77 if (put_user(gid, grouplist+i))
78 return -EFAULT;
79 }
80 return 0;
81}
82
83/* fill a group_info from a user-space array - it must be allocated already */
84static int groups_from_user(struct group_info *group_info,
85 gid_t __user *grouplist)
86{
87 struct user_namespace *user_ns = current_user_ns();
88 int i;
89 unsigned int count = group_info->ngroups;
90
91 for (i = 0; i < count; i++) {
92 gid_t gid;
93 kgid_t kgid;
94 if (get_user(gid, grouplist+i))
95 return -EFAULT;
96
97 kgid = make_kgid(user_ns, gid);
98 if (!gid_valid(kgid))
99 return -EINVAL;
100
101 GROUP_AT(group_info, i) = kgid;
102 }
103 return 0;
104}
105
106/* a simple Shell sort */
107static void groups_sort(struct group_info *group_info)
108{
109 int base, max, stride;
110 int gidsetsize = group_info->ngroups;
111
112 for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
113 ; /* nothing */
114 stride /= 3;
115
116 while (stride) {
117 max = gidsetsize - stride;
118 for (base = 0; base < max; base++) {
119 int left = base;
120 int right = left + stride;
121 kgid_t tmp = GROUP_AT(group_info, right);
122
123 while (left >= 0 && gid_gt(GROUP_AT(group_info, left), tmp)) {
124 GROUP_AT(group_info, right) =
125 GROUP_AT(group_info, left);
126 right = left;
127 left -= stride;
128 }
129 GROUP_AT(group_info, right) = tmp;
130 }
131 stride /= 3;
132 }
133}
134
135/* a simple bsearch */
136int groups_search(const struct group_info *group_info, kgid_t grp)
137{
138 unsigned int left, right;
139
140 if (!group_info)
141 return 0;
142
143 left = 0;
144 right = group_info->ngroups;
145 while (left < right) {
146 unsigned int mid = (left+right)/2;
147 if (gid_gt(grp, GROUP_AT(group_info, mid)))
148 left = mid + 1;
149 else if (gid_lt(grp, GROUP_AT(group_info, mid)))
150 right = mid;
151 else
152 return 1;
153 }
154 return 0;
155}
156
157/**
158 * set_groups - Change a group subscription in a set of credentials
159 * @new: The newly prepared set of credentials to alter
160 * @group_info: The group list to install
161 */
162void set_groups(struct cred *new, struct group_info *group_info)
163{
164 put_group_info(new->group_info);
165 groups_sort(group_info);
166 get_group_info(group_info);
167 new->group_info = group_info;
168}
169
170EXPORT_SYMBOL(set_groups);
171
172/**
173 * set_current_groups - Change current's group subscription
174 * @group_info: The group list to impose
175 *
176 * Validate a group subscription and, if valid, impose it upon current's task
177 * security record.
178 */
179int set_current_groups(struct group_info *group_info)
180{
181 struct cred *new;
182
183 new = prepare_creds();
184 if (!new)
185 return -ENOMEM;
186
187 set_groups(new, group_info);
188 return commit_creds(new);
189}
190
191EXPORT_SYMBOL(set_current_groups);
192
193SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
194{
195 const struct cred *cred = current_cred();
196 int i;
197
198 if (gidsetsize < 0)
199 return -EINVAL;
200
201 /* no need to grab task_lock here; it cannot change */
202 i = cred->group_info->ngroups;
203 if (gidsetsize) {
204 if (i > gidsetsize) {
205 i = -EINVAL;
206 goto out;
207 }
208 if (groups_to_user(grouplist, cred->group_info)) {
209 i = -EFAULT;
210 goto out;
211 }
212 }
213out:
214 return i;
215}
216
217bool may_setgroups(void)
218{
219 struct user_namespace *user_ns = current_user_ns();
220
221 return ns_capable(user_ns, CAP_SETGID) &&
222 userns_may_setgroups(user_ns);
223}
224
225/*
226 * SMP: Our groups are copy-on-write. We can set them safely
227 * without another task interfering.
228 */
229
230SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
231{
232 struct group_info *group_info;
233 int retval;
234
235 if (!may_setgroups())
236 return -EPERM;
237 if ((unsigned)gidsetsize > NGROUPS_MAX)
238 return -EINVAL;
239
240 group_info = groups_alloc(gidsetsize);
241 if (!group_info)
242 return -ENOMEM;
243 retval = groups_from_user(group_info, grouplist);
244 if (retval) {
245 put_group_info(group_info);
246 return retval;
247 }
248
249 retval = set_current_groups(group_info);
250 put_group_info(group_info);
251
252 return retval;
253}
254
255/*
256 * Check whether we're fsgid/egid or in the supplemental group..
257 */
258int in_group_p(kgid_t grp)
259{
260 const struct cred *cred = current_cred();
261 int retval = 1;
262
263 if (!gid_eq(grp, cred->fsgid))
264 retval = groups_search(cred->group_info, grp);
265 return retval;
266}
267
268EXPORT_SYMBOL(in_group_p);
269
270int in_egroup_p(kgid_t grp)
271{
272 const struct cred *cred = current_cred();
273 int retval = 1;
274
275 if (!gid_eq(grp, cred->egid))
276 retval = groups_search(cred->group_info, grp);
277 return retval;
278}
279
280EXPORT_SYMBOL(in_egroup_p);