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path: root/kernel/groups.c (plain)
blob: 94bde5210e3d5ec0dfaa893f735ed9613e1a127b
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 <linux/vmalloc.h>
11#include <asm/uaccess.h>
12
13struct group_info *groups_alloc(int gidsetsize)
14{
15 struct group_info *gi;
16 unsigned int len;
17
18 len = sizeof(struct group_info) + sizeof(kgid_t) * gidsetsize;
19 gi = kmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_NOWARN|__GFP_NORETRY);
20 if (!gi)
21 gi = __vmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_HIGHMEM, PAGE_KERNEL);
22 if (!gi)
23 return NULL;
24
25 atomic_set(&gi->usage, 1);
26 gi->ngroups = gidsetsize;
27 return gi;
28}
29
30EXPORT_SYMBOL(groups_alloc);
31
32void groups_free(struct group_info *group_info)
33{
34 kvfree(group_info);
35}
36
37EXPORT_SYMBOL(groups_free);
38
39/* export the group_info to a user-space array */
40static int groups_to_user(gid_t __user *grouplist,
41 const struct group_info *group_info)
42{
43 struct user_namespace *user_ns = current_user_ns();
44 int i;
45 unsigned int count = group_info->ngroups;
46
47 for (i = 0; i < count; i++) {
48 gid_t gid;
49 gid = from_kgid_munged(user_ns, group_info->gid[i]);
50 if (put_user(gid, grouplist+i))
51 return -EFAULT;
52 }
53 return 0;
54}
55
56/* fill a group_info from a user-space array - it must be allocated already */
57static int groups_from_user(struct group_info *group_info,
58 gid_t __user *grouplist)
59{
60 struct user_namespace *user_ns = current_user_ns();
61 int i;
62 unsigned int count = group_info->ngroups;
63
64 for (i = 0; i < count; i++) {
65 gid_t gid;
66 kgid_t kgid;
67 if (get_user(gid, grouplist+i))
68 return -EFAULT;
69
70 kgid = make_kgid(user_ns, gid);
71 if (!gid_valid(kgid))
72 return -EINVAL;
73
74 group_info->gid[i] = kgid;
75 }
76 return 0;
77}
78
79/* a simple Shell sort */
80void groups_sort(struct group_info *group_info)
81{
82 int base, max, stride;
83 int gidsetsize = group_info->ngroups;
84
85 for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
86 ; /* nothing */
87 stride /= 3;
88
89 while (stride) {
90 max = gidsetsize - stride;
91 for (base = 0; base < max; base++) {
92 int left = base;
93 int right = left + stride;
94 kgid_t tmp = group_info->gid[right];
95
96 while (left >= 0 && gid_gt(group_info->gid[left], tmp)) {
97 group_info->gid[right] = group_info->gid[left];
98 right = left;
99 left -= stride;
100 }
101 group_info->gid[right] = tmp;
102 }
103 stride /= 3;
104 }
105}
106EXPORT_SYMBOL(groups_sort);
107
108/* a simple bsearch */
109int groups_search(const struct group_info *group_info, kgid_t grp)
110{
111 unsigned int left, right;
112
113 if (!group_info)
114 return 0;
115
116 left = 0;
117 right = group_info->ngroups;
118 while (left < right) {
119 unsigned int mid = (left+right)/2;
120 if (gid_gt(grp, group_info->gid[mid]))
121 left = mid + 1;
122 else if (gid_lt(grp, group_info->gid[mid]))
123 right = mid;
124 else
125 return 1;
126 }
127 return 0;
128}
129
130/**
131 * set_groups - Change a group subscription in a set of credentials
132 * @new: The newly prepared set of credentials to alter
133 * @group_info: The group list to install
134 */
135void set_groups(struct cred *new, struct group_info *group_info)
136{
137 put_group_info(new->group_info);
138 get_group_info(group_info);
139 new->group_info = group_info;
140}
141
142EXPORT_SYMBOL(set_groups);
143
144/**
145 * set_current_groups - Change current's group subscription
146 * @group_info: The group list to impose
147 *
148 * Validate a group subscription and, if valid, impose it upon current's task
149 * security record.
150 */
151int set_current_groups(struct group_info *group_info)
152{
153 struct cred *new;
154
155 new = prepare_creds();
156 if (!new)
157 return -ENOMEM;
158
159 set_groups(new, group_info);
160 return commit_creds(new);
161}
162
163EXPORT_SYMBOL(set_current_groups);
164
165SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
166{
167 const struct cred *cred = current_cred();
168 int i;
169
170 if (gidsetsize < 0)
171 return -EINVAL;
172
173 /* no need to grab task_lock here; it cannot change */
174 i = cred->group_info->ngroups;
175 if (gidsetsize) {
176 if (i > gidsetsize) {
177 i = -EINVAL;
178 goto out;
179 }
180 if (groups_to_user(grouplist, cred->group_info)) {
181 i = -EFAULT;
182 goto out;
183 }
184 }
185out:
186 return i;
187}
188
189bool may_setgroups(void)
190{
191 struct user_namespace *user_ns = current_user_ns();
192
193 return ns_capable(user_ns, CAP_SETGID) &&
194 userns_may_setgroups(user_ns);
195}
196
197/*
198 * SMP: Our groups are copy-on-write. We can set them safely
199 * without another task interfering.
200 */
201
202SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
203{
204 struct group_info *group_info;
205 int retval;
206
207 if (!may_setgroups())
208 return -EPERM;
209 if ((unsigned)gidsetsize > NGROUPS_MAX)
210 return -EINVAL;
211
212 group_info = groups_alloc(gidsetsize);
213 if (!group_info)
214 return -ENOMEM;
215 retval = groups_from_user(group_info, grouplist);
216 if (retval) {
217 put_group_info(group_info);
218 return retval;
219 }
220
221 groups_sort(group_info);
222 retval = set_current_groups(group_info);
223 put_group_info(group_info);
224
225 return retval;
226}
227
228/*
229 * Check whether we're fsgid/egid or in the supplemental group..
230 */
231int in_group_p(kgid_t grp)
232{
233 const struct cred *cred = current_cred();
234 int retval = 1;
235
236 if (!gid_eq(grp, cred->fsgid))
237 retval = groups_search(cred->group_info, grp);
238 return retval;
239}
240
241EXPORT_SYMBOL(in_group_p);
242
243int in_egroup_p(kgid_t grp)
244{
245 const struct cred *cred = current_cred();
246 int retval = 1;
247
248 if (!gid_eq(grp, cred->egid))
249 retval = groups_search(cred->group_info, grp);
250 return retval;
251}
252
253EXPORT_SYMBOL(in_egroup_p);
254
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