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/sort.h> 9 #include <linux/syscalls.h> 10 #include <linux/user_namespace.h> 11 #include <linux/vmalloc.h> 12 #include <linux/uaccess.h> 13 14 struct group_info *groups_alloc(int gidsetsize) 15 { 16 struct group_info *gi; 17 unsigned int len; 18 19 len = sizeof(struct group_info) + sizeof(kgid_t) * gidsetsize; 20 gi = kmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_NOWARN|__GFP_NORETRY); 21 if (!gi) 22 gi = __vmalloc(len, GFP_KERNEL_ACCOUNT, PAGE_KERNEL); 23 if (!gi) 24 return NULL; 25 26 atomic_set(&gi->usage, 1); 27 gi->ngroups = gidsetsize; 28 return gi; 29 } 30 31 EXPORT_SYMBOL(groups_alloc); 32 33 void groups_free(struct group_info *group_info) 34 { 35 kvfree(group_info); 36 } 37 38 EXPORT_SYMBOL(groups_free); 39 40 /* export the group_info to a user-space array */ 41 static int groups_to_user(gid_t __user *grouplist, 42 const struct group_info *group_info) 43 { 44 struct user_namespace *user_ns = current_user_ns(); 45 int i; 46 unsigned int count = group_info->ngroups; 47 48 for (i = 0; i < count; i++) { 49 gid_t gid; 50 gid = from_kgid_munged(user_ns, group_info->gid[i]); 51 if (put_user(gid, grouplist+i)) 52 return -EFAULT; 53 } 54 return 0; 55 } 56 57 /* fill a group_info from a user-space array - it must be allocated already */ 58 static int groups_from_user(struct group_info *group_info, 59 gid_t __user *grouplist) 60 { 61 struct user_namespace *user_ns = current_user_ns(); 62 int i; 63 unsigned int count = group_info->ngroups; 64 65 for (i = 0; i < count; i++) { 66 gid_t gid; 67 kgid_t kgid; 68 if (get_user(gid, grouplist+i)) 69 return -EFAULT; 70 71 kgid = make_kgid(user_ns, gid); 72 if (!gid_valid(kgid)) 73 return -EINVAL; 74 75 group_info->gid[i] = kgid; 76 } 77 return 0; 78 } 79 80 static int gid_cmp(const void *_a, const void *_b) 81 { 82 kgid_t a = *(kgid_t *)_a; 83 kgid_t b = *(kgid_t *)_b; 84 85 return gid_gt(a, b) - gid_lt(a, b); 86 } 87 88 static void groups_sort(struct group_info *group_info) 89 { 90 sort(group_info->gid, group_info->ngroups, sizeof(*group_info->gid), 91 gid_cmp, NULL); 92 } 93 94 /* a simple bsearch */ 95 int groups_search(const struct group_info *group_info, kgid_t grp) 96 { 97 unsigned int left, right; 98 99 if (!group_info) 100 return 0; 101 102 left = 0; 103 right = group_info->ngroups; 104 while (left < right) { 105 unsigned int mid = (left+right)/2; 106 if (gid_gt(grp, group_info->gid[mid])) 107 left = mid + 1; 108 else if (gid_lt(grp, group_info->gid[mid])) 109 right = mid; 110 else 111 return 1; 112 } 113 return 0; 114 } 115 116 /** 117 * set_groups - Change a group subscription in a set of credentials 118 * @new: The newly prepared set of credentials to alter 119 * @group_info: The group list to install 120 */ 121 void set_groups(struct cred *new, struct group_info *group_info) 122 { 123 put_group_info(new->group_info); 124 groups_sort(group_info); 125 get_group_info(group_info); 126 new->group_info = group_info; 127 } 128 129 EXPORT_SYMBOL(set_groups); 130 131 /** 132 * set_current_groups - Change current's group subscription 133 * @group_info: The group list to impose 134 * 135 * Validate a group subscription and, if valid, impose it upon current's task 136 * security record. 137 */ 138 int set_current_groups(struct group_info *group_info) 139 { 140 struct cred *new; 141 142 new = prepare_creds(); 143 if (!new) 144 return -ENOMEM; 145 146 set_groups(new, group_info); 147 return commit_creds(new); 148 } 149 150 EXPORT_SYMBOL(set_current_groups); 151 152 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist) 153 { 154 const struct cred *cred = current_cred(); 155 int i; 156 157 if (gidsetsize < 0) 158 return -EINVAL; 159 160 /* no need to grab task_lock here; it cannot change */ 161 i = cred->group_info->ngroups; 162 if (gidsetsize) { 163 if (i > gidsetsize) { 164 i = -EINVAL; 165 goto out; 166 } 167 if (groups_to_user(grouplist, cred->group_info)) { 168 i = -EFAULT; 169 goto out; 170 } 171 } 172 out: 173 return i; 174 } 175 176 bool may_setgroups(void) 177 { 178 struct user_namespace *user_ns = current_user_ns(); 179 180 return ns_capable(user_ns, CAP_SETGID) && 181 userns_may_setgroups(user_ns); 182 } 183 184 /* 185 * SMP: Our groups are copy-on-write. We can set them safely 186 * without another task interfering. 187 */ 188 189 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist) 190 { 191 struct group_info *group_info; 192 int retval; 193 194 if (!may_setgroups()) 195 return -EPERM; 196 if ((unsigned)gidsetsize > NGROUPS_MAX) 197 return -EINVAL; 198 199 group_info = groups_alloc(gidsetsize); 200 if (!group_info) 201 return -ENOMEM; 202 retval = groups_from_user(group_info, grouplist); 203 if (retval) { 204 put_group_info(group_info); 205 return retval; 206 } 207 208 retval = set_current_groups(group_info); 209 put_group_info(group_info); 210 211 return retval; 212 } 213 214 /* 215 * Check whether we're fsgid/egid or in the supplemental group.. 216 */ 217 int in_group_p(kgid_t grp) 218 { 219 const struct cred *cred = current_cred(); 220 int retval = 1; 221 222 if (!gid_eq(grp, cred->fsgid)) 223 retval = groups_search(cred->group_info, grp); 224 return retval; 225 } 226 227 EXPORT_SYMBOL(in_group_p); 228 229 int in_egroup_p(kgid_t grp) 230 { 231 const struct cred *cred = current_cred(); 232 int retval = 1; 233 234 if (!gid_eq(grp, cred->egid)) 235 retval = groups_search(cred->group_info, grp); 236 return retval; 237 } 238 239 EXPORT_SYMBOL(in_egroup_p); 240