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 unsigned int len; 19 20 len = sizeof(struct group_info) + sizeof(kgid_t) * gidsetsize; 21 gi = kmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_NOWARN|__GFP_NORETRY); 22 if (!gi) 23 gi = __vmalloc(len, GFP_KERNEL_ACCOUNT); 24 if (!gi) 25 return NULL; 26 27 atomic_set(&gi->usage, 1); 28 gi->ngroups = gidsetsize; 29 return gi; 30 } 31 32 EXPORT_SYMBOL(groups_alloc); 33 34 void groups_free(struct group_info *group_info) 35 { 36 kvfree(group_info); 37 } 38 39 EXPORT_SYMBOL(groups_free); 40 41 /* export the group_info to a user-space array */ 42 static int groups_to_user(gid_t __user *grouplist, 43 const struct group_info *group_info) 44 { 45 struct user_namespace *user_ns = current_user_ns(); 46 int i; 47 unsigned int count = group_info->ngroups; 48 49 for (i = 0; i < count; i++) { 50 gid_t gid; 51 gid = from_kgid_munged(user_ns, group_info->gid[i]); 52 if (put_user(gid, grouplist+i)) 53 return -EFAULT; 54 } 55 return 0; 56 } 57 58 /* fill a group_info from a user-space array - it must be allocated already */ 59 static int groups_from_user(struct group_info *group_info, 60 gid_t __user *grouplist) 61 { 62 struct user_namespace *user_ns = current_user_ns(); 63 int i; 64 unsigned int count = group_info->ngroups; 65 66 for (i = 0; i < count; i++) { 67 gid_t gid; 68 kgid_t kgid; 69 if (get_user(gid, grouplist+i)) 70 return -EFAULT; 71 72 kgid = make_kgid(user_ns, gid); 73 if (!gid_valid(kgid)) 74 return -EINVAL; 75 76 group_info->gid[i] = kgid; 77 } 78 return 0; 79 } 80 81 static int gid_cmp(const void *_a, const void *_b) 82 { 83 kgid_t a = *(kgid_t *)_a; 84 kgid_t b = *(kgid_t *)_b; 85 86 return gid_gt(a, b) - gid_lt(a, b); 87 } 88 89 void groups_sort(struct group_info *group_info) 90 { 91 sort(group_info->gid, group_info->ngroups, sizeof(*group_info->gid), 92 gid_cmp, NULL); 93 } 94 EXPORT_SYMBOL(groups_sort); 95 96 /* a simple bsearch */ 97 int groups_search(const struct group_info *group_info, kgid_t grp) 98 { 99 unsigned int left, right; 100 101 if (!group_info) 102 return 0; 103 104 left = 0; 105 right = group_info->ngroups; 106 while (left < right) { 107 unsigned int mid = (left+right)/2; 108 if (gid_gt(grp, group_info->gid[mid])) 109 left = mid + 1; 110 else if (gid_lt(grp, group_info->gid[mid])) 111 right = mid; 112 else 113 return 1; 114 } 115 return 0; 116 } 117 118 /** 119 * set_groups - Change a group subscription in a set of credentials 120 * @new: The newly prepared set of credentials to alter 121 * @group_info: The group list to install 122 */ 123 void set_groups(struct cred *new, struct group_info *group_info) 124 { 125 put_group_info(new->group_info); 126 get_group_info(group_info); 127 new->group_info = group_info; 128 } 129 130 EXPORT_SYMBOL(set_groups); 131 132 /** 133 * set_current_groups - Change current's group subscription 134 * @group_info: The group list to impose 135 * 136 * Validate a group subscription and, if valid, impose it upon current's task 137 * security record. 138 */ 139 int set_current_groups(struct group_info *group_info) 140 { 141 struct cred *new; 142 143 new = prepare_creds(); 144 if (!new) 145 return -ENOMEM; 146 147 set_groups(new, group_info); 148 return commit_creds(new); 149 } 150 151 EXPORT_SYMBOL(set_current_groups); 152 153 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist) 154 { 155 const struct cred *cred = current_cred(); 156 int i; 157 158 if (gidsetsize < 0) 159 return -EINVAL; 160 161 /* no need to grab task_lock here; it cannot change */ 162 i = cred->group_info->ngroups; 163 if (gidsetsize) { 164 if (i > gidsetsize) { 165 i = -EINVAL; 166 goto out; 167 } 168 if (groups_to_user(grouplist, cred->group_info)) { 169 i = -EFAULT; 170 goto out; 171 } 172 } 173 out: 174 return i; 175 } 176 177 bool may_setgroups(void) 178 { 179 struct user_namespace *user_ns = current_user_ns(); 180 181 return ns_capable_setid(user_ns, CAP_SETGID) && 182 userns_may_setgroups(user_ns); 183 } 184 185 /* 186 * SMP: Our groups are copy-on-write. We can set them safely 187 * without another task interfering. 188 */ 189 190 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist) 191 { 192 struct group_info *group_info; 193 int retval; 194 195 if (!may_setgroups()) 196 return -EPERM; 197 if ((unsigned)gidsetsize > NGROUPS_MAX) 198 return -EINVAL; 199 200 group_info = groups_alloc(gidsetsize); 201 if (!group_info) 202 return -ENOMEM; 203 retval = groups_from_user(group_info, grouplist); 204 if (retval) { 205 put_group_info(group_info); 206 return retval; 207 } 208 209 groups_sort(group_info); 210 retval = set_current_groups(group_info); 211 put_group_info(group_info); 212 213 return retval; 214 } 215 216 /* 217 * Check whether we're fsgid/egid or in the supplemental group.. 218 */ 219 int in_group_p(kgid_t grp) 220 { 221 const struct cred *cred = current_cred(); 222 int retval = 1; 223 224 if (!gid_eq(grp, cred->fsgid)) 225 retval = groups_search(cred->group_info, grp); 226 return retval; 227 } 228 229 EXPORT_SYMBOL(in_group_p); 230 231 int in_egroup_p(kgid_t grp) 232 { 233 const struct cred *cred = current_cred(); 234 int retval = 1; 235 236 if (!gid_eq(grp, cred->egid)) 237 retval = groups_search(cred->group_info, grp); 238 return retval; 239 } 240 241 EXPORT_SYMBOL(in_egroup_p); 242