2 * Supplementary group IDs
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>
12 /* init to 2 - one for init_task, one to ensure it is never freed */
13 struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
15 struct group_info *groups_alloc(int gidsetsize)
17 struct group_info *group_info;
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);
27 group_info->ngroups = gidsetsize;
28 group_info->nblocks = nblocks;
29 atomic_set(&group_info->usage, 1);
31 if (gidsetsize <= NGROUPS_SMALL)
32 group_info->blocks[0] = group_info->small_block;
34 for (i = 0; i < nblocks; i++) {
36 b = (void *)__get_free_page(GFP_USER);
38 goto out_undo_partial_alloc;
39 group_info->blocks[i] = b;
44 out_undo_partial_alloc:
46 free_page((unsigned long)group_info->blocks[i]);
52 EXPORT_SYMBOL(groups_alloc);
54 void groups_free(struct group_info *group_info)
56 if (group_info->blocks[0] != group_info->small_block) {
58 for (i = 0; i < group_info->nblocks; i++)
59 free_page((unsigned long)group_info->blocks[i]);
64 EXPORT_SYMBOL(groups_free);
66 /* export the group_info to a user-space array */
67 static int groups_to_user(gid_t __user *grouplist,
68 const struct group_info *group_info)
70 struct user_namespace *user_ns = current_user_ns();
72 unsigned int count = group_info->ngroups;
74 for (i = 0; i < count; i++) {
76 gid = from_kgid_munged(user_ns, GROUP_AT(group_info, i));
77 if (put_user(gid, grouplist+i))
83 /* fill a group_info from a user-space array - it must be allocated already */
84 static int groups_from_user(struct group_info *group_info,
85 gid_t __user *grouplist)
87 struct user_namespace *user_ns = current_user_ns();
89 unsigned int count = group_info->ngroups;
91 for (i = 0; i < count; i++) {
94 if (get_user(gid, grouplist+i))
97 kgid = make_kgid(user_ns, gid);
101 GROUP_AT(group_info, i) = kgid;
106 /* a simple Shell sort */
107 static void groups_sort(struct group_info *group_info)
109 int base, max, stride;
110 int gidsetsize = group_info->ngroups;
112 for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
117 max = gidsetsize - stride;
118 for (base = 0; base < max; base++) {
120 int right = left + stride;
121 kgid_t tmp = GROUP_AT(group_info, right);
123 while (left >= 0 && gid_gt(GROUP_AT(group_info, left), tmp)) {
124 GROUP_AT(group_info, right) =
125 GROUP_AT(group_info, left);
129 GROUP_AT(group_info, right) = tmp;
135 /* a simple bsearch */
136 int groups_search(const struct group_info *group_info, kgid_t grp)
138 unsigned int left, right;
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)))
149 else if (gid_lt(grp, GROUP_AT(group_info, mid)))
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
162 * Validate a group subscription and, if valid, insert it into a set
165 int set_groups(struct cred *new, struct group_info *group_info)
167 put_group_info(new->group_info);
168 groups_sort(group_info);
169 get_group_info(group_info);
170 new->group_info = group_info;
174 EXPORT_SYMBOL(set_groups);
177 * set_current_groups - Change current's group subscription
178 * @group_info: The group list to impose
180 * Validate a group subscription and, if valid, impose it upon current's task
183 int set_current_groups(struct group_info *group_info)
188 new = prepare_creds();
192 ret = set_groups(new, group_info);
198 return commit_creds(new);
201 EXPORT_SYMBOL(set_current_groups);
203 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
205 const struct cred *cred = current_cred();
211 /* no need to grab task_lock here; it cannot change */
212 i = cred->group_info->ngroups;
214 if (i > gidsetsize) {
218 if (groups_to_user(grouplist, cred->group_info)) {
227 bool may_setgroups(void)
229 struct user_namespace *user_ns = current_user_ns();
231 return ns_capable(user_ns, CAP_SETGID) &&
232 userns_may_setgroups(user_ns);
236 * SMP: Our groups are copy-on-write. We can set them safely
237 * without another task interfering.
240 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
242 struct group_info *group_info;
245 if (!may_setgroups())
247 if ((unsigned)gidsetsize > NGROUPS_MAX)
250 group_info = groups_alloc(gidsetsize);
253 retval = groups_from_user(group_info, grouplist);
255 put_group_info(group_info);
259 retval = set_current_groups(group_info);
260 put_group_info(group_info);
266 * Check whether we're fsgid/egid or in the supplemental group..
268 int in_group_p(kgid_t grp)
270 const struct cred *cred = current_cred();
273 if (!gid_eq(grp, cred->fsgid))
274 retval = groups_search(cred->group_info, grp);
278 EXPORT_SYMBOL(in_group_p);
280 int in_egroup_p(kgid_t grp)
282 const struct cred *cred = current_cred();
285 if (!gid_eq(grp, cred->egid))
286 retval = groups_search(cred->group_info, grp);
290 EXPORT_SYMBOL(in_egroup_p);