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Linux/kernel/groups.c

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

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