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
12struct group_info *groups_alloc(int gidsetsize)
13{
14	struct group_info *group_info;
15	int nblocks;
16	int i;
17
18	nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;
19	/* Make sure we always allocate at least one indirect block pointer */
20	nblocks = nblocks ? : 1;
21	group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER);
22	if (!group_info)
23		return NULL;
24	group_info->ngroups = gidsetsize;
25	group_info->nblocks = nblocks;
26	atomic_set(&group_info->usage, 1);
27
28	if (gidsetsize <= NGROUPS_SMALL)
29		group_info->blocks[0] = group_info->small_block;
30	else {
31		for (i = 0; i < nblocks; i++) {
32			kgid_t *b;
33			b = (void *)__get_free_page(GFP_USER);
34			if (!b)
35				goto out_undo_partial_alloc;
36			group_info->blocks[i] = b;
37		}
38	}
39	return group_info;
40
41out_undo_partial_alloc:
42	while (--i >= 0) {
43		free_page((unsigned long)group_info->blocks[i]);
44	}
45	kfree(group_info);
46	return NULL;
47}
48
49EXPORT_SYMBOL(groups_alloc);
50
51void groups_free(struct group_info *group_info)
52{
53	if (group_info->blocks[0] != group_info->small_block) {
54		int i;
55		for (i = 0; i < group_info->nblocks; i++)
56			free_page((unsigned long)group_info->blocks[i]);
57	}
58	kfree(group_info);
59}
60
61EXPORT_SYMBOL(groups_free);
62
63/* export the group_info to a user-space array */
64static int groups_to_user(gid_t __user *grouplist,
65			  const struct group_info *group_info)
66{
67	struct user_namespace *user_ns = current_user_ns();
68	int i;
69	unsigned int count = group_info->ngroups;
70
71	for (i = 0; i < count; i++) {
72		gid_t gid;
73		gid = from_kgid_munged(user_ns, GROUP_AT(group_info, i));
74		if (put_user(gid, grouplist+i))
75			return -EFAULT;
76	}
77	return 0;
78}
79
80/* fill a group_info from a user-space array - it must be allocated already */
81static int groups_from_user(struct group_info *group_info,
82    gid_t __user *grouplist)
83{
84	struct user_namespace *user_ns = current_user_ns();
85	int i;
86	unsigned int count = group_info->ngroups;
87
88	for (i = 0; i < count; i++) {
89		gid_t gid;
90		kgid_t kgid;
91		if (get_user(gid, grouplist+i))
92			return -EFAULT;
93
94		kgid = make_kgid(user_ns, gid);
95		if (!gid_valid(kgid))
96			return -EINVAL;
97
98		GROUP_AT(group_info, i) = kgid;
99	}
100	return 0;
101}
102
103/* a simple Shell sort */
104static void groups_sort(struct group_info *group_info)
105{
106	int base, max, stride;
107	int gidsetsize = group_info->ngroups;
108
109	for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
110		; /* nothing */
111	stride /= 3;
112
113	while (stride) {
114		max = gidsetsize - stride;
115		for (base = 0; base < max; base++) {
116			int left = base;
117			int right = left + stride;
118			kgid_t tmp = GROUP_AT(group_info, right);
119
120			while (left >= 0 && gid_gt(GROUP_AT(group_info, left), tmp)) {
121				GROUP_AT(group_info, right) =
122				    GROUP_AT(group_info, left);
123				right = left;
124				left -= stride;
125			}
126			GROUP_AT(group_info, right) = tmp;
127		}
128		stride /= 3;
129	}
130}
131
132/* a simple bsearch */
133int groups_search(const struct group_info *group_info, kgid_t grp)
134{
135	unsigned int left, right;
136
137	if (!group_info)
138		return 0;
139
140	left = 0;
141	right = group_info->ngroups;
142	while (left < right) {
143		unsigned int mid = (left+right)/2;
144		if (gid_gt(grp, GROUP_AT(group_info, mid)))
145			left = mid + 1;
146		else if (gid_lt(grp, GROUP_AT(group_info, mid)))
147			right = mid;
148		else
149			return 1;
150	}
151	return 0;
152}
153
154/**
155 * set_groups - Change a group subscription in a set of credentials
156 * @new: The newly prepared set of credentials to alter
157 * @group_info: The group list to install
158 */
159void set_groups(struct cred *new, struct group_info *group_info)
160{
161	put_group_info(new->group_info);
162	groups_sort(group_info);
163	get_group_info(group_info);
164	new->group_info = group_info;
165}
166
167EXPORT_SYMBOL(set_groups);
168
169/**
170 * set_current_groups - Change current's group subscription
171 * @group_info: The group list to impose
172 *
173 * Validate a group subscription and, if valid, impose it upon current's task
174 * security record.
175 */
176int set_current_groups(struct group_info *group_info)
177{
178	struct cred *new;
179
180	new = prepare_creds();
181	if (!new)
182		return -ENOMEM;
183
184	set_groups(new, group_info);
185	return commit_creds(new);
186}
187
188EXPORT_SYMBOL(set_current_groups);
189
190SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
191{
192	const struct cred *cred = current_cred();
193	int i;
194
195	if (gidsetsize < 0)
196		return -EINVAL;
197
198	/* no need to grab task_lock here; it cannot change */
199	i = cred->group_info->ngroups;
200	if (gidsetsize) {
201		if (i > gidsetsize) {
202			i = -EINVAL;
203			goto out;
204		}
205		if (groups_to_user(grouplist, cred->group_info)) {
206			i = -EFAULT;
207			goto out;
208		}
209	}
210out:
211	return i;
212}
213
214bool may_setgroups(void)
215{
216	struct user_namespace *user_ns = current_user_ns();
217
218	return ns_capable(user_ns, CAP_SETGID) &&
219		userns_may_setgroups(user_ns);
220}
221
222/*
223 *	SMP: Our groups are copy-on-write. We can set them safely
224 *	without another task interfering.
225 */
226
227SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
228{
229	struct group_info *group_info;
230	int retval;
231
232	if (!may_setgroups())
233		return -EPERM;
234	if ((unsigned)gidsetsize > NGROUPS_MAX)
235		return -EINVAL;
236
237	group_info = groups_alloc(gidsetsize);
238	if (!group_info)
239		return -ENOMEM;
240	retval = groups_from_user(group_info, grouplist);
241	if (retval) {
242		put_group_info(group_info);
243		return retval;
244	}
245
246	retval = set_current_groups(group_info);
247	put_group_info(group_info);
248
249	return retval;
250}
251
252/*
253 * Check whether we're fsgid/egid or in the supplemental group..
254 */
255int in_group_p(kgid_t grp)
256{
257	const struct cred *cred = current_cred();
258	int retval = 1;
259
260	if (!gid_eq(grp, cred->fsgid))
261		retval = groups_search(cred->group_info, grp);
262	return retval;
263}
264
265EXPORT_SYMBOL(in_group_p);
266
267int in_egroup_p(kgid_t grp)
268{
269	const struct cred *cred = current_cred();
270	int retval = 1;
271
272	if (!gid_eq(grp, cred->egid))
273		retval = groups_search(cred->group_info, grp);
274	return retval;
275}
276
277EXPORT_SYMBOL(in_egroup_p);
278