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 atomic_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; 137 138 new = prepare_creds(); 139 if (!new) 140 return -ENOMEM; 141 142 set_groups(new, group_info); 143 return commit_creds(new); 144 } 145 146 EXPORT_SYMBOL(set_current_groups); 147 148 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist) 149 { 150 const struct cred *cred = current_cred(); 151 int i; 152 153 if (gidsetsize < 0) 154 return -EINVAL; 155 156 /* no need to grab task_lock here; it cannot change */ 157 i = cred->group_info->ngroups; 158 if (gidsetsize) { 159 if (i > gidsetsize) { 160 i = -EINVAL; 161 goto out; 162 } 163 if (groups_to_user(grouplist, cred->group_info)) { 164 i = -EFAULT; 165 goto out; 166 } 167 } 168 out: 169 return i; 170 } 171 172 bool may_setgroups(void) 173 { 174 struct user_namespace *user_ns = current_user_ns(); 175 176 return ns_capable_setid(user_ns, CAP_SETGID) && 177 userns_may_setgroups(user_ns); 178 } 179 180 /* 181 * SMP: Our groups are copy-on-write. We can set them safely 182 * without another task interfering. 183 */ 184 185 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist) 186 { 187 struct group_info *group_info; 188 int retval; 189 190 if (!may_setgroups()) 191 return -EPERM; 192 if ((unsigned)gidsetsize > NGROUPS_MAX) 193 return -EINVAL; 194 195 group_info = groups_alloc(gidsetsize); 196 if (!group_info) 197 return -ENOMEM; 198 retval = groups_from_user(group_info, grouplist); 199 if (retval) { 200 put_group_info(group_info); 201 return retval; 202 } 203 204 groups_sort(group_info); 205 retval = set_current_groups(group_info); 206 put_group_info(group_info); 207 208 return retval; 209 } 210 211 /* 212 * Check whether we're fsgid/egid or in the supplemental group.. 213 */ 214 int in_group_p(kgid_t grp) 215 { 216 const struct cred *cred = current_cred(); 217 int retval = 1; 218 219 if (!gid_eq(grp, cred->fsgid)) 220 retval = groups_search(cred->group_info, grp); 221 return retval; 222 } 223 224 EXPORT_SYMBOL(in_group_p); 225 226 int in_egroup_p(kgid_t grp) 227 { 228 const struct cred *cred = current_cred(); 229 int retval = 1; 230 231 if (!gid_eq(grp, cred->egid)) 232 retval = groups_search(cred->group_info, grp); 233 return retval; 234 } 235 236 EXPORT_SYMBOL(in_egroup_p); 237