projects/linux·blob v3.16-rc5 · refs

271 lines · 5.8 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 <asm/uaccess.h>
10
11/* init to 2 - one for init_task, one to ensure it is never freed */
12struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
13
14struct group_info *groups_alloc(int gidsetsize)
15{
16 struct group_info *group_info;
17 int nblocks;
18 int i;
19
20 nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;
21 /* Make sure we always allocate at least one indirect block pointer */
22 nblocks = nblocks ? : 1;
23 group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER);
24 if (!group_info)
25 return NULL;
26 group_info->ngroups = gidsetsize;
27 group_info->nblocks = nblocks;
28 atomic_set(&group_info->usage, 1);
29
30 if (gidsetsize <= NGROUPS_SMALL)
31 group_info->blocks[0] = group_info->small_block;
32 else {
33 for (i = 0; i < nblocks; i++) {
34 kgid_t *b;
35 b = (void *)__get_free_page(GFP_USER);
36 if (!b)
37 goto out_undo_partial_alloc;
38 group_info->blocks[i] = b;
39 }
40 }
41 return group_info;
42
43out_undo_partial_alloc:
44 while (--i >= 0) {
45 free_page((unsigned long)group_info->blocks[i]);
46 }
47 kfree(group_info);
48 return NULL;
49}
50
51EXPORT_SYMBOL(groups_alloc);
52
53void groups_free(struct group_info *group_info)
54{
55 if (group_info->blocks[0] != group_info->small_block) {
56 int i;
57 for (i = 0; i < group_info->nblocks; i++)
58 free_page((unsigned long)group_info->blocks[i]);
59 }
60 kfree(group_info);
61}
62
63EXPORT_SYMBOL(groups_free);
64
65/* export the group_info to a user-space array */
66static int groups_to_user(gid_t __user *grouplist,
67 const struct group_info *group_info)
68{
69 struct user_namespace *user_ns = current_user_ns();
70 int i;
71 unsigned int count = group_info->ngroups;
72
73 for (i = 0; i < count; i++) {
74 gid_t gid;
75 gid = from_kgid_munged(user_ns, GROUP_AT(group_info, i));
76 if (put_user(gid, grouplist+i))
77 return -EFAULT;
78 }
79 return 0;
80}
81
82/* fill a group_info from a user-space array - it must be allocated already */
83static int groups_from_user(struct group_info *group_info,
84 gid_t __user *grouplist)
85{
86 struct user_namespace *user_ns = current_user_ns();
87 int i;
88 unsigned int count = group_info->ngroups;
89
90 for (i = 0; i < count; i++) {
91 gid_t gid;
92 kgid_t kgid;
93 if (get_user(gid, grouplist+i))
94 return -EFAULT;
95
96 kgid = make_kgid(user_ns, gid);
97 if (!gid_valid(kgid))
98 return -EINVAL;
99
100 GROUP_AT(group_info, i) = kgid;
101 }
102 return 0;
103}
104
105/* a simple Shell sort */
106static void groups_sort(struct group_info *group_info)
107{
108 int base, max, stride;
109 int gidsetsize = group_info->ngroups;
110
111 for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
112 ; /* nothing */
113 stride /= 3;
114
115 while (stride) {
116 max = gidsetsize - stride;
117 for (base = 0; base < max; base++) {
118 int left = base;
119 int right = left + stride;
120 kgid_t tmp = GROUP_AT(group_info, right);
121
122 while (left >= 0 && gid_gt(GROUP_AT(group_info, left), tmp)) {
123 GROUP_AT(group_info, right) =
124 GROUP_AT(group_info, left);
125 right = left;
126 left -= stride;
127 }
128 GROUP_AT(group_info, right) = tmp;
129 }
130 stride /= 3;
131 }
132}
133
134/* a simple bsearch */
135int groups_search(const struct group_info *group_info, kgid_t grp)
136{
137 unsigned int left, right;
138
139 if (!group_info)
140 return 0;
141
142 left = 0;
143 right = group_info->ngroups;
144 while (left < right) {
145 unsigned int mid = (left+right)/2;
146 if (gid_gt(grp, GROUP_AT(group_info, mid)))
147 left = mid + 1;
148 else if (gid_lt(grp, GROUP_AT(group_info, mid)))
149 right = mid;
150 else
151 return 1;
152 }
153 return 0;
154}
155
156/**
157 * set_groups - Change a group subscription in a set of credentials
158 * @new: The newly prepared set of credentials to alter
159 * @group_info: The group list to install
160 */
161void set_groups(struct cred *new, struct group_info *group_info)
162{
163 put_group_info(new->group_info);
164 groups_sort(group_info);
165 get_group_info(group_info);
166 new->group_info = group_info;
167}
168
169EXPORT_SYMBOL(set_groups);
170
171/**
172 * set_current_groups - Change current's group subscription
173 * @group_info: The group list to impose
174 *
175 * Validate a group subscription and, if valid, impose it upon current's task
176 * security record.
177 */
178int set_current_groups(struct group_info *group_info)
179{
180 struct cred *new;
181
182 new = prepare_creds();
183 if (!new)
184 return -ENOMEM;
185
186 set_groups(new, group_info);
187 return commit_creds(new);
188}
189
190EXPORT_SYMBOL(set_current_groups);
191
192SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
193{
194 const struct cred *cred = current_cred();
195 int i;
196
197 if (gidsetsize < 0)
198 return -EINVAL;
199
200 /* no need to grab task_lock here; it cannot change */
201 i = cred->group_info->ngroups;
202 if (gidsetsize) {
203 if (i > gidsetsize) {
204 i = -EINVAL;
205 goto out;
206 }
207 if (groups_to_user(grouplist, cred->group_info)) {
208 i = -EFAULT;
209 goto out;
210 }
211 }
212out:
213 return i;
214}
215
216/*
217 * SMP: Our groups are copy-on-write. We can set them safely
218 * without another task interfering.
219 */
220
221SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
222{
223 struct group_info *group_info;
224 int retval;
225
226 if (!ns_capable(current_user_ns(), CAP_SETGID))
227 return -EPERM;
228 if ((unsigned)gidsetsize > NGROUPS_MAX)
229 return -EINVAL;
230
231 group_info = groups_alloc(gidsetsize);
232 if (!group_info)
233 return -ENOMEM;
234 retval = groups_from_user(group_info, grouplist);
235 if (retval) {
236 put_group_info(group_info);
237 return retval;
238 }
239
240 retval = set_current_groups(group_info);
241 put_group_info(group_info);
242
243 return retval;
244}
245
246/*
247 * Check whether we're fsgid/egid or in the supplemental group..
248 */
249int in_group_p(kgid_t grp)
250{
251 const struct cred *cred = current_cred();
252 int retval = 1;
253
254 if (!gid_eq(grp, cred->fsgid))
255 retval = groups_search(cred->group_info, grp);
256 return retval;
257}
258
259EXPORT_SYMBOL(in_group_p);
260
261int in_egroup_p(kgid_t grp)
262{
263 const struct cred *cred = current_cred();
264 int retval = 1;
265
266 if (!gid_eq(grp, cred->egid))
267 retval = groups_search(cred->group_info, grp);
268 return retval;
269}
270
271EXPORT_SYMBOL(in_egroup_p);