/*
   * Supplementary group IDs
   */
  #include <linux/cred.h>

  #include <linux/export.h>

  #include <linux/slab.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <asm/uaccess.h>
  
  /* init to 2 - one for init_task, one to ensure it is never freed */
  struct group_info init_groups = { .usage = ATOMIC_INIT(2) };
  
  struct group_info *groups_alloc(int gidsetsize)
  {
  	struct group_info *group_info;
  	int nblocks;
  	int i;
  
  	nblocks = (gidsetsize + NGROUPS_PER_BLOCK - 1) / NGROUPS_PER_BLOCK;
  	/* Make sure we always allocate at least one indirect block pointer */
  	nblocks = nblocks ? : 1;
  	group_info = kmalloc(sizeof(*group_info) + nblocks*sizeof(gid_t *), GFP_USER);
  	if (!group_info)
  		return NULL;
  	group_info->ngroups = gidsetsize;
  	group_info->nblocks = nblocks;
  	atomic_set(&group_info->usage, 1);
  
  	if (gidsetsize <= NGROUPS_SMALL)
  		group_info->blocks[0] = group_info->small_block;
  	else {
  		for (i = 0; i < nblocks; i++) {

  			kgid_t *b;

  			b = (void *)__get_free_page(GFP_USER);
  			if (!b)
  				goto out_undo_partial_alloc;
  			group_info->blocks[i] = b;
  		}
  	}
  	return group_info;
  
  out_undo_partial_alloc:
  	while (--i >= 0) {
  		free_page((unsigned long)group_info->blocks[i]);
  	}
  	kfree(group_info);
  	return NULL;
  }
  
  EXPORT_SYMBOL(groups_alloc);
  
  void groups_free(struct group_info *group_info)
  {
  	if (group_info->blocks[0] != group_info->small_block) {
  		int i;
  		for (i = 0; i < group_info->nblocks; i++)
  			free_page((unsigned long)group_info->blocks[i]);
  	}
  	kfree(group_info);
  }
  
  EXPORT_SYMBOL(groups_free);
  
  /* export the group_info to a user-space array */
  static int groups_to_user(gid_t __user *grouplist,
  			  const struct group_info *group_info)
  {

  	struct user_namespace *user_ns = current_user_ns();

  	int i;
  	unsigned int count = group_info->ngroups;

  	for (i = 0; i < count; i++) {
  		gid_t gid;
  		gid = from_kgid_munged(user_ns, GROUP_AT(group_info, i));
  		if (put_user(gid, grouplist+i))

  			return -EFAULT;

  	}
  	return 0;
  }
  
  /* fill a group_info from a user-space array - it must be allocated already */
  static int groups_from_user(struct group_info *group_info,
      gid_t __user *grouplist)
  {

  	struct user_namespace *user_ns = current_user_ns();

  	int i;
  	unsigned int count = group_info->ngroups;

  	for (i = 0; i < count; i++) {
  		gid_t gid;
  		kgid_t kgid;
  		if (get_user(gid, grouplist+i))

  			return -EFAULT;

  		kgid = make_kgid(user_ns, gid);
  		if (!gid_valid(kgid))
  			return -EINVAL;
  
  		GROUP_AT(group_info, i) = kgid;

  	}
  	return 0;
  }
  
  /* a simple Shell sort */
  static void groups_sort(struct group_info *group_info)
  {
  	int base, max, stride;
  	int gidsetsize = group_info->ngroups;
  
  	for (stride = 1; stride < gidsetsize; stride = 3 * stride + 1)
  		; /* nothing */
  	stride /= 3;
  
  	while (stride) {
  		max = gidsetsize - stride;
  		for (base = 0; base < max; base++) {
  			int left = base;
  			int right = left + stride;

  			kgid_t tmp = GROUP_AT(group_info, right);

  			while (left >= 0 && gid_gt(GROUP_AT(group_info, left), tmp)) {

  				GROUP_AT(group_info, right) =
  				    GROUP_AT(group_info, left);
  				right = left;
  				left -= stride;
  			}
  			GROUP_AT(group_info, right) = tmp;
  		}
  		stride /= 3;
  	}
  }
  
  /* a simple bsearch */

  int groups_search(const struct group_info *group_info, kgid_t grp)

  {
  	unsigned int left, right;
  
  	if (!group_info)
  		return 0;
  
  	left = 0;
  	right = group_info->ngroups;
  	while (left < right) {
  		unsigned int mid = (left+right)/2;

  		if (gid_gt(grp, GROUP_AT(group_info, mid)))

  			left = mid + 1;

  		else if (gid_lt(grp, GROUP_AT(group_info, mid)))

  			right = mid;
  		else
  			return 1;
  	}
  	return 0;
  }
  
  /**
   * set_groups - Change a group subscription in a set of credentials
   * @new: The newly prepared set of credentials to alter
   * @group_info: The group list to install

   */

  void set_groups(struct cred *new, struct group_info *group_info)

  {

  	put_group_info(new->group_info);
  	groups_sort(group_info);
  	get_group_info(group_info);
  	new->group_info = group_info;

  }
  
  EXPORT_SYMBOL(set_groups);
  
  /**
   * set_current_groups - Change current's group subscription
   * @group_info: The group list to impose
   *
   * Validate a group subscription and, if valid, impose it upon current's task
   * security record.
   */
  int set_current_groups(struct group_info *group_info)
  {
  	struct cred *new;

  
  	new = prepare_creds();
  	if (!new)
  		return -ENOMEM;

  	set_groups(new, group_info);

  	return commit_creds(new);
  }
  
  EXPORT_SYMBOL(set_current_groups);
  
  SYSCALL_DEFINE2(getgroups, int, gidsetsize, gid_t __user *, grouplist)
  {
  	const struct cred *cred = current_cred();
  	int i;
  
  	if (gidsetsize < 0)
  		return -EINVAL;
  
  	/* no need to grab task_lock here; it cannot change */
  	i = cred->group_info->ngroups;
  	if (gidsetsize) {
  		if (i > gidsetsize) {
  			i = -EINVAL;
  			goto out;
  		}
  		if (groups_to_user(grouplist, cred->group_info)) {
  			i = -EFAULT;
  			goto out;
  		}
  	}
  out:
  	return i;
  }
  
  /*
   *	SMP: Our groups are copy-on-write. We can set them safely
   *	without another task interfering.
   */
  
  SYSCALL_DEFINE2(setgroups, int, gidsetsize, gid_t __user *, grouplist)
  {
  	struct group_info *group_info;
  	int retval;

  	if (!ns_capable(current_user_ns(), CAP_SETGID))

  		return -EPERM;
  	if ((unsigned)gidsetsize > NGROUPS_MAX)
  		return -EINVAL;
  
  	group_info = groups_alloc(gidsetsize);
  	if (!group_info)
  		return -ENOMEM;
  	retval = groups_from_user(group_info, grouplist);
  	if (retval) {
  		put_group_info(group_info);
  		return retval;
  	}
  
  	retval = set_current_groups(group_info);
  	put_group_info(group_info);
  
  	return retval;
  }
  
  /*
   * Check whether we're fsgid/egid or in the supplemental group..
   */

  int in_group_p(kgid_t grp)

  {
  	const struct cred *cred = current_cred();
  	int retval = 1;

  	if (!gid_eq(grp, cred->fsgid))
  		retval = groups_search(cred->group_info, grp);

  	return retval;
  }
  
  EXPORT_SYMBOL(in_group_p);

  int in_egroup_p(kgid_t grp)

  {
  	const struct cred *cred = current_cred();
  	int retval = 1;

  	if (!gid_eq(grp, cred->egid))
  		retval = groups_search(cred->group_info, grp);

  	return retval;
  }
  
  EXPORT_SYMBOL(in_egroup_p);