kernel/groups.c

   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/syscalls.h>
   9 #include <linux/user_namespace.h>
  10 #include <linux/vmalloc.h>
  11 #include <linux/uaccess.h>
  12
  13 struct group_info *groups_alloc(int gidsetsize)
  14 {
  15         struct group_info *gi;
  16         unsigned int len;
  17
  18         len = sizeof(struct group_info) + sizeof(kgid_t) * gidsetsize;
  19         gi = kmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_NOWARN|__GFP_NORETRY);
  20         if (!gi)
  21                 gi = __vmalloc(len, GFP_KERNEL_ACCOUNT|__GFP_HIGHMEM, PAGE_KERNEL);
  22         if (!gi)
  23                 return NULL;
  24
  25         atomic_set(&gi->usage, 1);
  26         gi->ngroups = gidsetsize;
  27         return gi;
  28 }
  29
  30 EXPORT_SYMBOL(groups_alloc);
  31
  32 void groups_free(struct group_info *group_info)
  33 {
  34         kvfree(group_info);
  35 }
  36
  37 EXPORT_SYMBOL(groups_free);
  38
  39 /* export the group_info to a user-space array */
  40 static int groups_to_user(gid_t __user *grouplist,
  41                           const struct group_info *group_info)
  42 {
  43         struct user_namespace *user_ns = current_user_ns();
  44         int i;
  45         unsigned int count = group_info->ngroups;
  46
  47         for (i = 0; i < count; i++) {
  48                 gid_t gid;
  49                 gid = from_kgid_munged(user_ns, group_info->gid[i]);
  50                 if (put_user(gid, grouplist+i))
  51                         return -EFAULT;
  52         }
  53         return 0;
  54 }
  55
  56 /* fill a group_info from a user-space array - it must be allocated already */
  57 static int groups_from_user(struct group_info *group_info,
  58     gid_t __user *grouplist)
  59 {
  60         struct user_namespace *user_ns = current_user_ns();
  61         int i;
  62         unsigned int count = group_info->ngroups;
  63
  64         for (i = 0; i < count; i++) {
  65                 gid_t gid;
  66                 kgid_t kgid;
  67                 if (get_user(gid, grouplist+i))
  68                         return -EFAULT;
  69
  70                 kgid = make_kgid(user_ns, gid);
  71                 if (!gid_valid(kgid))
  72                         return -EINVAL;
  73
  74                 group_info->gid[i] = kgid;
  75         }
  76         return 0;
  77 }
  78
  79 /* a simple Shell sort */
  80 static void groups_sort(struct group_info *group_info)
  81 {
  82         int base, max, stride;
  83         int gidsetsize = group_info->ngroups;
  84
  85         for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
  86                 ; /* nothing */
  87         stride /= 3;
  88
  89         while (stride) {
  90                 max = gidsetsize - stride;
  91                 for (base = 0; base < max; base++) {
  92                         int left = base;
  93                         int right = left + stride;
  94                         kgid_t tmp = group_info->gid[right];
  95
  96                         while (left >= 0 && gid_gt(group_info->gid[left], tmp)) {
  97                                 group_info->gid[right] = group_info->gid[left];
  98                                 right = left;
  99                                 left -= stride;
 100                         }
 101                         group_info->gid[right] = tmp;
 102                 }
 103                 stride /= 3;
 104         }
 105 }
 106
 107 /* a simple bsearch */
 108 int groups_search(const struct group_info *group_info, kgid_t grp)
 109 {
 110         unsigned int left, right;
 111
 112         if (!group_info)
 113                 return 0;
 114
 115         left = 0;
 116         right = group_info->ngroups;
 117         while (left < right) {
 118                 unsigned int mid = (left+right)/2;
 119                 if (gid_gt(grp, group_info->gid[mid]))
 120                         left = mid + 1;
 121                 else if (gid_lt(grp, group_info->gid[mid]))
 122                         right = mid;
 123                 else
 124                         return 1;
 125         }
 126         return 0;
 127 }
 128
 129 /**
 130  * set_groups - Change a group subscription in a set of credentials
 131  * @new: The newly prepared set of credentials to alter
 132  * @group_info: The group list to install
 133  */
 134 void set_groups(struct cred *new, struct group_info *group_info)
 135 {
 136         put_group_info(new->group_info);
 137         groups_sort(group_info);
 138         get_group_info(group_info);
 139         new->group_info = group_info;
 140 }
 141
 142 EXPORT_SYMBOL(set_groups);
 143
 144 /**
 145  * set_current_groups - Change current's group subscription
 146  * @group_info: The group list to impose
 147  *
 148  * Validate a group subscription and, if valid, impose it upon current's task
 149  * security record.
 150  */
 151 int set_current_groups(struct group_info *group_info)
 152 {
 153         struct cred *new;
 154
 155         new = prepare_creds();
 156         if (!new)
 157                 return -ENOMEM;
 158
 159         set_groups(new, group_info);
 160         return commit_creds(new);
 161 }
 162
 163 EXPORT_SYMBOL(set_current_groups);
 164
 165 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
 166 {
 167         const struct cred *cred = current_cred();
 168         int i;
 169
 170         if (gidsetsize < 0)
 171                 return -EINVAL;
 172
 173         /* no need to grab task_lock here; it cannot change */
 174         i = cred->group_info->ngroups;
 175         if (gidsetsize) {
 176                 if (i > gidsetsize) {
 177                         i = -EINVAL;
 178                         goto out;
 179                 }
 180                 if (groups_to_user(grouplist, cred->group_info)) {
 181                         i = -EFAULT;
 182                         goto out;
 183                 }
 184         }
 185 out:
 186         return i;
 187 }
 188
 189 bool may_setgroups(void)
 190 {
 191         struct user_namespace *user_ns = current_user_ns();
 192
 193         return ns_capable(user_ns, CAP_SETGID) &&
 194                 userns_may_setgroups(user_ns);
 195 }
 196
 197 /*
 198  *      SMP: Our groups are copy-on-write. We can set them safely
 199  *      without another task interfering.
 200  */
 201
 202 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
 203 {
 204         struct group_info *group_info;
 205         int retval;
 206
 207         if (!may_setgroups())
 208                 return -EPERM;
 209         if ((unsigned)gidsetsize > NGROUPS_MAX)
 210                 return -EINVAL;
 211
 212         group_info = groups_alloc(gidsetsize);
 213         if (!group_info)
 214                 return -ENOMEM;
 215         retval = groups_from_user(group_info, grouplist);
 216         if (retval) {
 217                 put_group_info(group_info);
 218                 return retval;
 219         }
 220
 221         retval = set_current_groups(group_info);
 222         put_group_info(group_info);
 223
 224         return retval;
 225 }
 226
 227 /*
 228  * Check whether we're fsgid/egid or in the supplemental group..
 229  */
 230 int in_group_p(kgid_t grp)
 231 {
 232         const struct cred *cred = current_cred();
 233         int retval = 1;
 234
 235         if (!gid_eq(grp, cred->fsgid))
 236                 retval = groups_search(cred->group_info, grp);
 237         return retval;
 238 }
 239
 240 EXPORT_SYMBOL(in_group_p);
 241
 242 int in_egroup_p(kgid_t grp)
 243 {
 244         const struct cred *cred = current_cred();
 245         int retval = 1;
 246
 247         if (!gid_eq(grp, cred->egid))
 248                 retval = groups_search(cred->group_info, grp);
 249         return retval;
 250 }
 251
 252 EXPORT_SYMBOL(in_egroup_p);