| 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, PAGE_KERNEL); |
| 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 | static 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 | |
| 95 | /* a simple bsearch */ |
| 96 | int groups_search(const struct group_info *group_info, kgid_t grp) |
| 97 | { |
| 98 | unsigned int left, right; |
| 99 | |
| 100 | if (!group_info) |
| 101 | return 0; |
| 102 | |
| 103 | left = 0; |
| 104 | right = group_info->ngroups; |
| 105 | while (left < right) { |
| 106 | unsigned int mid = (left+right)/2; |
| 107 | if (gid_gt(grp, group_info->gid[mid])) |
| 108 | left = mid + 1; |
| 109 | else if (gid_lt(grp, group_info->gid[mid])) |
| 110 | right = mid; |
| 111 | else |
| 112 | return 1; |
| 113 | } |
| 114 | return 0; |
| 115 | } |
| 116 | |
| 117 | /** |
| 118 | * set_groups - Change a group subscription in a set of credentials |
| 119 | * @new: The newly prepared set of credentials to alter |
| 120 | * @group_info: The group list to install |
| 121 | */ |
| 122 | void set_groups(struct cred *new, struct group_info *group_info) |
| 123 | { |
| 124 | put_group_info(new->group_info); |
| 125 | groups_sort(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(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 | retval = set_current_groups(group_info); |
| 210 | put_group_info(group_info); |
| 211 | |
| 212 | return retval; |
| 213 | } |
| 214 | |
| 215 | /* |
| 216 | * Check whether we're fsgid/egid or in the supplemental group.. |
| 217 | */ |
| 218 | int in_group_p(kgid_t grp) |
| 219 | { |
| 220 | const struct cred *cred = current_cred(); |
| 221 | int retval = 1; |
| 222 | |
| 223 | if (!gid_eq(grp, cred->fsgid)) |
| 224 | retval = groups_search(cred->group_info, grp); |
| 225 | return retval; |
| 226 | } |
| 227 | |
| 228 | EXPORT_SYMBOL(in_group_p); |
| 229 | |
| 230 | int in_egroup_p(kgid_t grp) |
| 231 | { |
| 232 | const struct cred *cred = current_cred(); |
| 233 | int retval = 1; |
| 234 | |
| 235 | if (!gid_eq(grp, cred->egid)) |
| 236 | retval = groups_search(cred->group_info, grp); |
| 237 | return retval; |
| 238 | } |
| 239 | |
| 240 | EXPORT_SYMBOL(in_egroup_p); |