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(&gi->usage, 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(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(user_ns, 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(user_ns, gid); 68 if (!gid_valid(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(a, b) - gid_lt(a, b); 82 } 83 84 void groups_sort(struct group_info *group_info) 85 { 86 sort(group_info->gid, group_info->ngroups, sizeof(*group_info->gid), 87 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(grp, group_info->gid[mid])) 104 left = mid + 1; 105 else if (gid_lt(grp, 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(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, 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(user_ns, CAP_SETGID) && 190 userns_may_setgroups(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(grp, cred->fsgid)) 233 retval = groups_search(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(grp, cred->egid)) 245 retval = groups_search(cred->group_info, grp); 246 return retval; 247 } 248 249 EXPORT_SYMBOL(in_egroup_p); 250