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