groups.c

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SearchContext: - none - 3 - 10

    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 <asm/uaccess.h>
   10 
   11 /* init to 2 - one for init_task, one to ensure it is never freed */
   12 struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
   13 
   14 struct group_info *groups_alloc(int gidsetsize)
   15 {
   16         struct group_info *group_info;
   17         int nblocks;
   18         int i;
   19 
   20         nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;
   21         /* Make sure we always allocate at least one indirect block pointer */
   22         nblocks = nblocks ? : 1;
   23         group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER);
   24         if (!group_info)
   25                 return NULL;
   26         group_info->ngroups = gidsetsize;
   27         group_info->nblocks = nblocks;
   28         atomic_set(&group_info->usage, 1);
   29 
   30         if (gidsetsize <= NGROUPS_SMALL)
   31                 group_info->blocks[0] = group_info->small_block;
   32         else {
   33                 for (i = 0; i < nblocks; i++) {
   34                         kgid_t *b;
   35                         b = (void *)__get_free_page(GFP_USER);
   36                         if (!b)
   37                                 goto out_undo_partial_alloc;
   38                         group_info->blocks[i] = b;
   39                 }
   40         }
   41         return group_info;
   42 
   43 out_undo_partial_alloc:
   44         while (--i >= 0) {
   45                 free_page((unsigned long)group_info->blocks[i]);
   46         }
   47         kfree(group_info);
   48         return NULL;
   49 }
   50 
   51 EXPORT_SYMBOL(groups_alloc);
   52 
   53 void groups_free(struct group_info *group_info)
   54 {
   55         if (group_info->blocks[0] != group_info->small_block) {
   56                 int i;
   57                 for (i = 0; i < group_info->nblocks; i++)
   58                         free_page((unsigned long)group_info->blocks[i]);
   59         }
   60         kfree(group_info);
   61 }
   62 
   63 EXPORT_SYMBOL(groups_free);
   64 
   65 /* export the group_info to a user-space array */
   66 static int groups_to_user(gid_t __user *grouplist,
   67                           const struct group_info *group_info)
   68 {
   69         struct user_namespace *user_ns = current_user_ns();
   70         int i;
   71         unsigned int count = group_info->ngroups;
   72 
   73         for (i = 0; i < count; i++) {
   74                 gid_t gid;
   75                 gid = from_kgid_munged(user_ns, GROUP_AT(group_info, i));
   76                 if (put_user(gid, grouplist+i))
   77                         return -EFAULT;
   78         }
   79         return 0;
   80 }
   81 
   82 /* fill a group_info from a user-space array - it must be allocated already */
   83 static int groups_from_user(struct group_info *group_info,
   84     gid_t __user *grouplist)
   85 {
   86         struct user_namespace *user_ns = current_user_ns();
   87         int i;
   88         unsigned int count = group_info->ngroups;
   89 
   90         for (i = 0; i < count; i++) {
   91                 gid_t gid;
   92                 kgid_t kgid;
   93                 if (get_user(gid, grouplist+i))
   94                         return -EFAULT;
   95 
   96                 kgid = make_kgid(user_ns, gid);
   97                 if (!gid_valid(kgid))
   98                         return -EINVAL;
   99 
  100                 GROUP_AT(group_info, i) = kgid;
  101         }
  102         return 0;
  103 }
  104 
  105 /* a simple Shell sort */
  106 static void groups_sort(struct group_info *group_info)
  107 {
  108         int base, max, stride;
  109         int gidsetsize = group_info->ngroups;
  110 
  111         for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
  112                 ; /* nothing */
  113         stride /= 3;
  114 
  115         while (stride) {
  116                 max = gidsetsize - stride;
  117                 for (base = 0; base < max; base++) {
  118                         int left = base;
  119                         int right = left + stride;
  120                         kgid_t tmp = GROUP_AT(group_info, right);
  121 
  122                         while (left >= 0 && gid_gt(GROUP_AT(group_info, left), tmp)) {
  123                                 GROUP_AT(group_info, right) =
  124                                     GROUP_AT(group_info, left);
  125                                 right = left;
  126                                 left -= stride;
  127                         }
  128                         GROUP_AT(group_info, right) = tmp;
  129                 }
  130                 stride /= 3;
  131         }
  132 }
  133 
  134 /* a simple bsearch */
  135 int groups_search(const struct group_info *group_info, kgid_t grp)
  136 {
  137         unsigned int left, right;
  138 
  139         if (!group_info)
  140                 return 0;
  141 
  142         left = 0;
  143         right = group_info->ngroups;
  144         while (left < right) {
  145                 unsigned int mid = (left+right)/2;
  146                 if (gid_gt(grp, GROUP_AT(group_info, mid)))
  147                         left = mid + 1;
  148                 else if (gid_lt(grp, GROUP_AT(group_info, mid)))
  149                         right = mid;
  150                 else
  151                         return 1;
  152         }
  153         return 0;
  154 }
  155 
  156 /**
  157  * set_groups - Change a group subscription in a set of credentials
  158  * @new: The newly prepared set of credentials to alter
  159  * @group_info: The group list to install
  160  *
  161  * Validate a group subscription and, if valid, insert it into a set
  162  * of credentials.
  163  */
  164 int set_groups(struct cred *new, struct group_info *group_info)
  165 {
  166         put_group_info(new->group_info);
  167         groups_sort(group_info);
  168         get_group_info(group_info);
  169         new->group_info = group_info;
  170         return 0;
  171 }
  172 
  173 EXPORT_SYMBOL(set_groups);
  174 
  175 /**
  176  * set_current_groups - Change current's group subscription
  177  * @group_info: The group list to impose
  178  *
  179  * Validate a group subscription and, if valid, impose it upon current's task
  180  * security record.
  181  */
  182 int set_current_groups(struct group_info *group_info)
  183 {
  184         struct cred *new;
  185         int ret;
  186 
  187         new = prepare_creds();
  188         if (!new)
  189                 return -ENOMEM;
  190 
  191         ret = set_groups(new, group_info);
  192         if (ret < 0) {
  193                 abort_creds(new);
  194                 return ret;
  195         }
  196 
  197         return commit_creds(new);
  198 }
  199 
  200 EXPORT_SYMBOL(set_current_groups);
  201 
  202 SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
  203 {
  204         const struct cred *cred = current_cred();
  205         int i;
  206 
  207         if (gidsetsize < 0)
  208                 return -EINVAL;
  209 
  210         /* no need to grab task_lock here; it cannot change */
  211         i = cred->group_info->ngroups;
  212         if (gidsetsize) {
  213                 if (i > gidsetsize) {
  214                         i = -EINVAL;
  215                         goto out;
  216                 }
  217                 if (groups_to_user(grouplist, cred->group_info)) {
  218                         i = -EFAULT;
  219                         goto out;
  220                 }
  221         }
  222 out:
  223         return i;
  224 }
  225 
  226 /*
  227  *      SMP: Our groups are copy-on-write. We can set them safely
  228  *      without another task interfering.
  229  */
  230 
  231 SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
  232 {
  233         struct group_info *group_info;
  234         int retval;
  235 
  236         if (!nsown_capable(CAP_SETGID))
  237                 return -EPERM;
  238         if ((unsigned)gidsetsize > NGROUPS_MAX)
  239                 return -EINVAL;
  240 
  241         group_info = groups_alloc(gidsetsize);
  242         if (!group_info)
  243                 return -ENOMEM;
  244         retval = groups_from_user(group_info, grouplist);
  245         if (retval) {
  246                 put_group_info(group_info);
  247                 return retval;
  248         }
  249 
  250         retval = set_current_groups(group_info);
  251         put_group_info(group_info);
  252 
  253         return retval;
  254 }
  255 
  256 /*
  257  * Check whether we're fsgid/egid or in the supplemental group..
  258  */
  259 int in_group_p(kgid_t grp)
  260 {
  261         const struct cred *cred = current_cred();
  262         int retval = 1;
  263 
  264         if (!gid_eq(grp, cred->fsgid))
  265                 retval = groups_search(cred->group_info, grp);
  266         return retval;
  267 }
  268 
  269 EXPORT_SYMBOL(in_group_p);
  270 
  271 int in_egroup_p(kgid_t grp)
  272 {
  273         const struct cred *cred = current_cred();
  274         int retval = 1;
  275 
  276         if (!gid_eq(grp, cred->egid))
  277                 retval = groups_search(cred->group_info, grp);
  278         return retval;
  279 }
  280 
  281 EXPORT_SYMBOL(in_egroup_p);

Cache object: 98221cb0a6d18f955012003a434e9867

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FreeBSD/Linux Kernel Cross Reference sys/kernel/groups.c

FreeBSD/Linux Kernel Cross Reference
sys/kernel/groups.c