2 * Supplementary group IDs
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>
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) };
14 struct group_info *groups_alloc(int gidsetsize)
16 struct group_info *group_info;
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);
26 group_info->ngroups = gidsetsize;
27 group_info->nblocks = nblocks;
28 atomic_set(&group_info->usage, 1);
30 if (gidsetsize <= NGROUPS_SMALL)
31 group_info->blocks[0] = group_info->small_block;
33 for (i = 0; i < nblocks; i++) {
35 b = (void *)__get_free_page(GFP_USER);
37 goto out_undo_partial_alloc;
38 group_info->blocks[i] = b;
43 out_undo_partial_alloc:
45 free_page((unsigned long)group_info->blocks[i]);
51 EXPORT_SYMBOL(groups_alloc);
53 void groups_free(struct group_info *group_info)
55 if (group_info->blocks[0] != group_info->small_block) {
57 for (i = 0; i < group_info->nblocks; i++)
58 free_page((unsigned long)group_info->blocks[i]);
63 EXPORT_SYMBOL(groups_free);
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)
70 unsigned int count = group_info->ngroups;
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);
76 if (copy_to_user(grouplist, group_info->blocks[i], len))
79 grouplist += NGROUPS_PER_BLOCK;
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)
90 unsigned int count = group_info->ngroups;
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);
96 if (copy_from_user(group_info->blocks[i], grouplist, len))
99 grouplist += NGROUPS_PER_BLOCK;
105 /* a simple Shell sort */
106 static void groups_sort(struct group_info *group_info)
108 int base, max, stride;
109 int gidsetsize = group_info->ngroups;
111 for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
116 max = gidsetsize - stride;
117 for (base = 0; base < max; base++) {
119 int right = left + stride;
120 gid_t tmp = GROUP_AT(group_info, right);
122 while (left >= 0 && GROUP_AT(group_info, left) > tmp) {
123 GROUP_AT(group_info, right) =
124 GROUP_AT(group_info, left);
128 GROUP_AT(group_info, right) = tmp;
134 /* a simple bsearch */
135 int groups_search(const struct group_info *group_info, gid_t grp)
137 unsigned int left, right;
143 right = group_info->ngroups;
144 while (left < right) {
145 unsigned int mid = (left+right)/2;
146 if (grp > GROUP_AT(group_info, mid))
148 else if (grp < GROUP_AT(group_info, mid))
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
161 * Validate a group subscription and, if valid, insert it into a set
164 int set_groups(struct cred *new, struct group_info *group_info)
168 retval = security_task_setgroups(group_info);
172 put_group_info(new->group_info);
173 groups_sort(group_info);
174 get_group_info(group_info);
175 new->group_info = group_info;
179 EXPORT_SYMBOL(set_groups);
182 * set_current_groups - Change current's group subscription
183 * @group_info: The group list to impose
185 * Validate a group subscription and, if valid, impose it upon current's task
188 int set_current_groups(struct group_info *group_info)
193 new = prepare_creds();
197 ret = set_groups(new, group_info);
203 return commit_creds(new);
206 EXPORT_SYMBOL(set_current_groups);
208 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
210 const struct cred *cred = current_cred();
216 /* no need to grab task_lock here; it cannot change */
217 i = cred->group_info->ngroups;
219 if (i > gidsetsize) {
223 if (groups_to_user(grouplist, cred->group_info)) {
233 * SMP: Our groups are copy-on-write. We can set them safely
234 * without another task interfering.
237 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
239 struct group_info *group_info;
242 if (!capable(CAP_SETGID))
244 if ((unsigned)gidsetsize > NGROUPS_MAX)
247 group_info = groups_alloc(gidsetsize);
250 retval = groups_from_user(group_info, grouplist);
252 put_group_info(group_info);
256 retval = set_current_groups(group_info);
257 put_group_info(group_info);
263 * Check whether we're fsgid/egid or in the supplemental group..
265 int in_group_p(gid_t grp)
267 const struct cred *cred = current_cred();
270 if (grp != cred->fsgid)
271 retval = groups_search(cred->group_info, grp);
275 EXPORT_SYMBOL(in_group_p);
277 int in_egroup_p(gid_t grp)
279 const struct cred *cred = current_cred();
282 if (grp != cred->egid)
283 retval = groups_search(cred->group_info, grp);
287 EXPORT_SYMBOL(in_egroup_p);