cgroup: Add generic cgroup subsystem permission checks.
[linux-2.6.git] / kernel / groups.c
1 /*
2  * Supplementary group IDs
3  */
4 #include <linux/cred.h>
5 #include <linux/module.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 */
12 struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
13
14 struct 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                         gid_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
43 out_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
51 EXPORT_SYMBOL(groups_alloc);
52
53 void 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
63 EXPORT_SYMBOL(groups_free);
64
65 /* export the group_info to a user-space array */
66 static int groups_to_user(gid_t __user *grouplist,
67                           const struct group_info *group_info)
68 {
69         int i;
70         unsigned int count = group_info->ngroups;
71
72         for (i = 0; i < group_info->nblocks; i++) {
73                 unsigned int cp_count = min(NGROUPS_PER_BLOCK, count);
74                 unsigned int len = cp_count * sizeof(*grouplist);
75
76                 if (copy_to_user(grouplist, group_info->blocks[i], len))
77                         return -EFAULT;
78
79                 grouplist += NGROUPS_PER_BLOCK;
80                 count -= cp_count;
81         }
82         return 0;
83 }
84
85 /* fill a group_info from a user-space array - it must be allocated already */
86 static int groups_from_user(struct group_info *group_info,
87     gid_t __user *grouplist)
88 {
89         int i;
90         unsigned int count = group_info->ngroups;
91
92         for (i = 0; i < group_info->nblocks; i++) {
93                 unsigned int cp_count = min(NGROUPS_PER_BLOCK, count);
94                 unsigned int len = cp_count * sizeof(*grouplist);
95
96                 if (copy_from_user(group_info->blocks[i], grouplist, len))
97                         return -EFAULT;
98
99                 grouplist += NGROUPS_PER_BLOCK;
100                 count -= cp_count;
101         }
102         return 0;
103 }
104
105 /* a simple Shell sort */
106 static 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                         gid_t tmp = GROUP_AT(group_info, right);
121
122                         while (left >= 0 && 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 */
135 int groups_search(const struct group_info *group_info, gid_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 (grp > GROUP_AT(group_info, mid))
147                         left = mid + 1;
148                 else if (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  *
161  * Validate a group subscription and, if valid, insert it into a set
162  * of credentials.
163  */
164 int set_groups(struct cred *new, struct group_info *group_info)
165 {
166         put_group_info(new->group_info);
167         groups_sort(group_info);
168         get_group_info(group_info);
169         new->group_info = group_info;
170         return 0;
171 }
172
173 EXPORT_SYMBOL(set_groups);
174
175 /**
176  * set_current_groups - Change current's group subscription
177  * @group_info: The group list to impose
178  *
179  * Validate a group subscription and, if valid, impose it upon current's task
180  * security record.
181  */
182 int set_current_groups(struct group_info *group_info)
183 {
184         struct cred *new;
185         int ret;
186
187         new = prepare_creds();
188         if (!new)
189                 return -ENOMEM;
190
191         ret = set_groups(new, group_info);
192         if (ret < 0) {
193                 abort_creds(new);
194                 return ret;
195         }
196
197         return commit_creds(new);
198 }
199
200 EXPORT_SYMBOL(set_current_groups);
201
202 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
203 {
204         const struct cred *cred = current_cred();
205         int i;
206
207         if (gidsetsize < 0)
208                 return -EINVAL;
209
210         /* no need to grab task_lock here; it cannot change */
211         i = cred->group_info->ngroups;
212         if (gidsetsize) {
213                 if (i > gidsetsize) {
214                         i = -EINVAL;
215                         goto out;
216                 }
217                 if (groups_to_user(grouplist, cred->group_info)) {
218                         i = -EFAULT;
219                         goto out;
220                 }
221         }
222 out:
223         return i;
224 }
225
226 /*
227  *      SMP: Our groups are copy-on-write. We can set them safely
228  *      without another task interfering.
229  */
230
231 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
232 {
233         struct group_info *group_info;
234         int retval;
235
236         if (!nsown_capable(CAP_SETGID))
237                 return -EPERM;
238         if ((unsigned)gidsetsize > NGROUPS_MAX)
239                 return -EINVAL;
240
241         group_info = groups_alloc(gidsetsize);
242         if (!group_info)
243                 return -ENOMEM;
244         retval = groups_from_user(group_info, grouplist);
245         if (retval) {
246                 put_group_info(group_info);
247                 return retval;
248         }
249
250         retval = set_current_groups(group_info);
251         put_group_info(group_info);
252
253         return retval;
254 }
255
256 /*
257  * Check whether we're fsgid/egid or in the supplemental group..
258  */
259 int in_group_p(gid_t grp)
260 {
261         const struct cred *cred = current_cred();
262         int retval = 1;
263
264         if (grp != cred->fsgid)
265                 retval = groups_search(cred->group_info, grp);
266         return retval;
267 }
268
269 EXPORT_SYMBOL(in_group_p);
270
271 int in_egroup_p(gid_t grp)
272 {
273         const struct cred *cred = current_cred();
274         int retval = 1;
275
276         if (grp != cred->egid)
277                 retval = groups_search(cred->group_info, grp);
278         return retval;
279 }
280
281 EXPORT_SYMBOL(in_egroup_p);