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/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);