1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Supplementary group IDs |
4 | */ |
5 | #include <linux/cred.h> |
6 | #include <linux/export.h> |
7 | #include <linux/slab.h> |
8 | #include <linux/security.h> |
9 | #include <linux/sort.h> |
10 | #include <linux/syscalls.h> |
11 | #include <linux/user_namespace.h> |
12 | #include <linux/vmalloc.h> |
13 | #include <linux/uaccess.h> |
14 | |
15 | struct group_info *groups_alloc(int gidsetsize) |
16 | { |
17 | struct group_info *gi; |
18 | gi = kvmalloc(struct_size(gi, gid, gidsetsize), GFP_KERNEL_ACCOUNT); |
19 | if (!gi) |
20 | return NULL; |
21 | |
22 | refcount_set(r: &gi->usage, n: 1); |
23 | gi->ngroups = gidsetsize; |
24 | return gi; |
25 | } |
26 | |
27 | EXPORT_SYMBOL(groups_alloc); |
28 | |
29 | void groups_free(struct group_info *group_info) |
30 | { |
31 | kvfree(addr: group_info); |
32 | } |
33 | |
34 | EXPORT_SYMBOL(groups_free); |
35 | |
36 | /* export the group_info to a user-space array */ |
37 | static int groups_to_user(gid_t __user *grouplist, |
38 | const struct group_info *group_info) |
39 | { |
40 | struct user_namespace *user_ns = current_user_ns(); |
41 | int i; |
42 | unsigned int count = group_info->ngroups; |
43 | |
44 | for (i = 0; i < count; i++) { |
45 | gid_t gid; |
46 | gid = from_kgid_munged(to: user_ns, gid: group_info->gid[i]); |
47 | if (put_user(gid, grouplist+i)) |
48 | return -EFAULT; |
49 | } |
50 | return 0; |
51 | } |
52 | |
53 | /* fill a group_info from a user-space array - it must be allocated already */ |
54 | static int groups_from_user(struct group_info *group_info, |
55 | gid_t __user *grouplist) |
56 | { |
57 | struct user_namespace *user_ns = current_user_ns(); |
58 | int i; |
59 | unsigned int count = group_info->ngroups; |
60 | |
61 | for (i = 0; i < count; i++) { |
62 | gid_t gid; |
63 | kgid_t kgid; |
64 | if (get_user(gid, grouplist+i)) |
65 | return -EFAULT; |
66 | |
67 | kgid = make_kgid(from: user_ns, gid); |
68 | if (!gid_valid(gid: kgid)) |
69 | return -EINVAL; |
70 | |
71 | group_info->gid[i] = kgid; |
72 | } |
73 | return 0; |
74 | } |
75 | |
76 | static int gid_cmp(const void *_a, const void *_b) |
77 | { |
78 | kgid_t a = *(kgid_t *)_a; |
79 | kgid_t b = *(kgid_t *)_b; |
80 | |
81 | return gid_gt(left: a, right: b) - gid_lt(left: a, right: b); |
82 | } |
83 | |
84 | void groups_sort(struct group_info *group_info) |
85 | { |
86 | sort(base: group_info->gid, num: group_info->ngroups, size: sizeof(*group_info->gid), |
87 | cmp_func: gid_cmp, NULL); |
88 | } |
89 | EXPORT_SYMBOL(groups_sort); |
90 | |
91 | /* a simple bsearch */ |
92 | int groups_search(const struct group_info *group_info, kgid_t grp) |
93 | { |
94 | unsigned int left, right; |
95 | |
96 | if (!group_info) |
97 | return 0; |
98 | |
99 | left = 0; |
100 | right = group_info->ngroups; |
101 | while (left < right) { |
102 | unsigned int mid = (left+right)/2; |
103 | if (gid_gt(left: grp, right: group_info->gid[mid])) |
104 | left = mid + 1; |
105 | else if (gid_lt(left: grp, right: group_info->gid[mid])) |
106 | right = mid; |
107 | else |
108 | return 1; |
109 | } |
110 | return 0; |
111 | } |
112 | |
113 | /** |
114 | * set_groups - Change a group subscription in a set of credentials |
115 | * @new: The newly prepared set of credentials to alter |
116 | * @group_info: The group list to install |
117 | */ |
118 | void set_groups(struct cred *new, struct group_info *group_info) |
119 | { |
120 | put_group_info(new->group_info); |
121 | get_group_info(gi: group_info); |
122 | new->group_info = group_info; |
123 | } |
124 | |
125 | EXPORT_SYMBOL(set_groups); |
126 | |
127 | /** |
128 | * set_current_groups - Change current's group subscription |
129 | * @group_info: The group list to impose |
130 | * |
131 | * Validate a group subscription and, if valid, impose it upon current's task |
132 | * security record. |
133 | */ |
134 | int set_current_groups(struct group_info *group_info) |
135 | { |
136 | struct cred *new; |
137 | const struct cred *old; |
138 | int retval; |
139 | |
140 | new = prepare_creds(); |
141 | if (!new) |
142 | return -ENOMEM; |
143 | |
144 | old = current_cred(); |
145 | |
146 | set_groups(new, group_info); |
147 | |
148 | retval = security_task_fix_setgroups(new, old); |
149 | if (retval < 0) |
150 | goto error; |
151 | |
152 | return commit_creds(new); |
153 | |
154 | error: |
155 | abort_creds(new); |
156 | return retval; |
157 | } |
158 | |
159 | EXPORT_SYMBOL(set_current_groups); |
160 | |
161 | SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist) |
162 | { |
163 | const struct cred *cred = current_cred(); |
164 | int i; |
165 | |
166 | if (gidsetsize < 0) |
167 | return -EINVAL; |
168 | |
169 | /* no need to grab task_lock here; it cannot change */ |
170 | i = cred->group_info->ngroups; |
171 | if (gidsetsize) { |
172 | if (i > gidsetsize) { |
173 | i = -EINVAL; |
174 | goto out; |
175 | } |
176 | if (groups_to_user(grouplist, group_info: cred->group_info)) { |
177 | i = -EFAULT; |
178 | goto out; |
179 | } |
180 | } |
181 | out: |
182 | return i; |
183 | } |
184 | |
185 | bool may_setgroups(void) |
186 | { |
187 | struct user_namespace *user_ns = current_user_ns(); |
188 | |
189 | return ns_capable_setid(ns: user_ns, CAP_SETGID) && |
190 | userns_may_setgroups(ns: user_ns); |
191 | } |
192 | |
193 | /* |
194 | * SMP: Our groups are copy-on-write. We can set them safely |
195 | * without another task interfering. |
196 | */ |
197 | |
198 | SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist) |
199 | { |
200 | struct group_info *group_info; |
201 | int retval; |
202 | |
203 | if (!may_setgroups()) |
204 | return -EPERM; |
205 | if ((unsigned)gidsetsize > NGROUPS_MAX) |
206 | return -EINVAL; |
207 | |
208 | group_info = groups_alloc(gidsetsize); |
209 | if (!group_info) |
210 | return -ENOMEM; |
211 | retval = groups_from_user(group_info, grouplist); |
212 | if (retval) { |
213 | put_group_info(group_info); |
214 | return retval; |
215 | } |
216 | |
217 | groups_sort(group_info); |
218 | retval = set_current_groups(group_info); |
219 | put_group_info(group_info); |
220 | |
221 | return retval; |
222 | } |
223 | |
224 | /* |
225 | * Check whether we're fsgid/egid or in the supplemental group.. |
226 | */ |
227 | int in_group_p(kgid_t grp) |
228 | { |
229 | const struct cred *cred = current_cred(); |
230 | int retval = 1; |
231 | |
232 | if (!gid_eq(left: grp, right: cred->fsgid)) |
233 | retval = groups_search(group_info: cred->group_info, grp); |
234 | return retval; |
235 | } |
236 | |
237 | EXPORT_SYMBOL(in_group_p); |
238 | |
239 | int in_egroup_p(kgid_t grp) |
240 | { |
241 | const struct cred *cred = current_cred(); |
242 | int retval = 1; |
243 | |
244 | if (!gid_eq(left: grp, right: cred->egid)) |
245 | retval = groups_search(group_info: cred->group_info, grp); |
246 | return retval; |
247 | } |
248 | |
249 | EXPORT_SYMBOL(in_egroup_p); |
250 | |