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 <asm/uaccess.h> 11 12 struct group_info *groups_alloc(int gidsetsize) 13 { 14 struct group_info *group_info; 15 int nblocks; 16 int i; 17 18 nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK; 19 /* Make sure we always allocate at least one indirect block pointer */ 20 nblocks = nblocks ? : 1; 21 group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER); 22 if (!group_info) 23 return NULL; 24 group_info->ngroups = gidsetsize; 25 group_info->nblocks = nblocks; 26 atomic_set(&group_info->usage, 1); 27 28 if (gidsetsize <= NGROUPS_SMALL) 29 group_info->blocks[0] = group_info->small_block; 30 else { 31 for (i = 0; i < nblocks; i++) { 32 kgid_t *b; 33 b = (void *)__get_free_page(GFP_USER); 34 if (!b) 35 goto out_undo_partial_alloc; 36 group_info->blocks[i] = b; 37 } 38 } 39 return group_info; 40 41 out_undo_partial_alloc: 42 while (--i >= 0) { 43 free_page((unsigned long)group_info->blocks[i]); 44 } 45 kfree(group_info); 46 return NULL; 47 } 48 49 EXPORT_SYMBOL(groups_alloc); 50 51 void groups_free(struct group_info *group_info) 52 { 53 if (group_info->blocks[0] != group_info->small_block) { 54 int i; 55 for (i = 0; i < group_info->nblocks; i++) 56 free_page((unsigned long)group_info->blocks[i]); 57 } 58 kfree(group_info); 59 } 60 61 EXPORT_SYMBOL(groups_free); 62 63 /* export the group_info to a user-space array */ 64 static int groups_to_user(gid_t __user *grouplist, 65 const struct group_info *group_info) 66 { 67 struct user_namespace *user_ns = current_user_ns(); 68 int i; 69 unsigned int count = group_info->ngroups; 70 71 for (i = 0; i < count; i++) { 72 gid_t gid; 73 gid = from_kgid_munged(user_ns, GROUP_AT(group_info, i)); 74 if (put_user(gid, grouplist+i)) 75 return -EFAULT; 76 } 77 return 0; 78 } 79 80 /* fill a group_info from a user-space array - it must be allocated already */ 81 static int groups_from_user(struct group_info *group_info, 82 gid_t __user *grouplist) 83 { 84 struct user_namespace *user_ns = current_user_ns(); 85 int i; 86 unsigned int count = group_info->ngroups; 87 88 for (i = 0; i < count; i++) { 89 gid_t gid; 90 kgid_t kgid; 91 if (get_user(gid, grouplist+i)) 92 return -EFAULT; 93 94 kgid = make_kgid(user_ns, gid); 95 if (!gid_valid(kgid)) 96 return -EINVAL; 97 98 GROUP_AT(group_info, i) = kgid; 99 } 100 return 0; 101 } 102 103 /* a simple Shell sort */ 104 static void groups_sort(struct group_info *group_info) 105 { 106 int base, max, stride; 107 int gidsetsize = group_info->ngroups; 108 109 for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1) 110 ; /* nothing */ 111 stride /= 3; 112 113 while (stride) { 114 max = gidsetsize - stride; 115 for (base = 0; base < max; base++) { 116 int left = base; 117 int right = left + stride; 118 kgid_t tmp = GROUP_AT(group_info, right); 119 120 while (left >= 0 && gid_gt(GROUP_AT(group_info, left), tmp)) { 121 GROUP_AT(group_info, right) = 122 GROUP_AT(group_info, left); 123 right = left; 124 left -= stride; 125 } 126 GROUP_AT(group_info, right) = tmp; 127 } 128 stride /= 3; 129 } 130 } 131 132 /* a simple bsearch */ 133 int groups_search(const struct group_info *group_info, kgid_t grp) 134 { 135 unsigned int left, right; 136 137 if (!group_info) 138 return 0; 139 140 left = 0; 141 right = group_info->ngroups; 142 while (left < right) { 143 unsigned int mid = (left+right)/2; 144 if (gid_gt(grp, GROUP_AT(group_info, mid))) 145 left = mid + 1; 146 else if (gid_lt(grp, GROUP_AT(group_info, mid))) 147 right = mid; 148 else 149 return 1; 150 } 151 return 0; 152 } 153 154 /** 155 * set_groups - Change a group subscription in a set of credentials 156 * @new: The newly prepared set of credentials to alter 157 * @group_info: The group list to install 158 */ 159 void set_groups(struct cred *new, struct group_info *group_info) 160 { 161 put_group_info(new->group_info); 162 groups_sort(group_info); 163 get_group_info(group_info); 164 new->group_info = group_info; 165 } 166 167 EXPORT_SYMBOL(set_groups); 168 169 /** 170 * set_current_groups - Change current's group subscription 171 * @group_info: The group list to impose 172 * 173 * Validate a group subscription and, if valid, impose it upon current's task 174 * security record. 175 */ 176 int set_current_groups(struct group_info *group_info) 177 { 178 struct cred *new; 179 180 new = prepare_creds(); 181 if (!new) 182 return -ENOMEM; 183 184 set_groups(new, group_info); 185 return commit_creds(new); 186 } 187 188 EXPORT_SYMBOL(set_current_groups); 189 190 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist) 191 { 192 const struct cred *cred = current_cred(); 193 int i; 194 195 if (gidsetsize < 0) 196 return -EINVAL; 197 198 /* no need to grab task_lock here; it cannot change */ 199 i = cred->group_info->ngroups; 200 if (gidsetsize) { 201 if (i > gidsetsize) { 202 i = -EINVAL; 203 goto out; 204 } 205 if (groups_to_user(grouplist, cred->group_info)) { 206 i = -EFAULT; 207 goto out; 208 } 209 } 210 out: 211 return i; 212 } 213 214 bool may_setgroups(void) 215 { 216 struct user_namespace *user_ns = current_user_ns(); 217 218 return ns_capable(user_ns, CAP_SETGID) && 219 userns_may_setgroups(user_ns); 220 } 221 222 /* 223 * SMP: Our groups are copy-on-write. We can set them safely 224 * without another task interfering. 225 */ 226 227 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist) 228 { 229 struct group_info *group_info; 230 int retval; 231 232 if (!may_setgroups()) 233 return -EPERM; 234 if ((unsigned)gidsetsize > NGROUPS_MAX) 235 return -EINVAL; 236 237 group_info = groups_alloc(gidsetsize); 238 if (!group_info) 239 return -ENOMEM; 240 retval = groups_from_user(group_info, grouplist); 241 if (retval) { 242 put_group_info(group_info); 243 return retval; 244 } 245 246 retval = set_current_groups(group_info); 247 put_group_info(group_info); 248 249 return retval; 250 } 251 252 /* 253 * Check whether we're fsgid/egid or in the supplemental group.. 254 */ 255 int in_group_p(kgid_t grp) 256 { 257 const struct cred *cred = current_cred(); 258 int retval = 1; 259 260 if (!gid_eq(grp, cred->fsgid)) 261 retval = groups_search(cred->group_info, grp); 262 return retval; 263 } 264 265 EXPORT_SYMBOL(in_group_p); 266 267 int in_egroup_p(kgid_t grp) 268 { 269 const struct cred *cred = current_cred(); 270 int retval = 1; 271 272 if (!gid_eq(grp, cred->egid)) 273 retval = groups_search(cred->group_info, grp); 274 return retval; 275 } 276 277 EXPORT_SYMBOL(in_egroup_p); 278