fs/lockd/svcshare.c

// SPDX-License-Identifier: GPL-2.0
/*
 * linux/fs/lockd/svcshare.c
 *
 * Management of DOS shares.
 *
 * Copyright (C) 1996 Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/time.h>
#include <linux/unistd.h>
#include <linux/string.h>
#include <linux/slab.h>

#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/svc.h>

#include "lockd.h"
#include "share.h"

static inline int
nlm_cmp_owner(struct lockd_share *share, struct xdr_netobj *oh)
{
	return share->s_owner.len == oh->len
	    && !memcmp(share->s_owner.data, oh->data, oh->len);
}

/*
 * Recompute s_access / s_mode as the union of every (access, deny) pair
 * whose bit is currently set in s_access_deny_bmap.
 */
static void nlm_recompute_share(struct lockd_share *share)
{
	u32 new_access = 0, new_mode = 0;
	unsigned int i;

	for (i = 0; i < 16; i++) {
		if (share->s_access_deny_bmap & BIT(i)) {
			new_access |= i >> 2;
			new_mode   |= i & 3;
		}
	}
	share->s_access = new_access;
	share->s_mode = new_mode;
}

/**
 * nlmsvc_share_file - create a share
 * @host: Network client peer
 * @file: File to be shared
 * @oh: Share owner handle
 * @access: Requested access mode
 * @mode: Requested file sharing mode
 *
 * Returns an NLM status code.
 */
__be32
nlmsvc_share_file(struct nlm_host *host, struct nlm_file *file,
		  struct xdr_netobj *oh, u32 access, u32 mode)
{
	struct lockd_share	*share;
	u8			*ohdata;

	if (nlmsvc_file_cannot_lock(file))
		return nlm_lck_denied_nolocks;

	for (share = file->f_shares; share; share = share->s_next) {
		if (share->s_host == host && nlm_cmp_owner(share, oh))
			goto update;
		if ((access & share->s_mode) || (mode & share->s_access))
			return nlm_lck_denied;
	}

	share = kmalloc(sizeof(*share) + oh->len, GFP_KERNEL);
	if (share == NULL)
		return nlm_lck_denied_nolocks;

	/* Copy owner handle */
	ohdata = (u8 *) (share + 1);
	memcpy(ohdata, oh->data, oh->len);

	share->s_file	    = file;
	share->s_host       = host;
	share->s_owner.data = ohdata;
	share->s_owner.len  = oh->len;
	share->s_access_deny_bmap  = 0;
	share->s_next       = file->f_shares;
	file->f_shares      = share;

update:
	share->s_access_deny_bmap |= LOCKD_FSH_BIT(access, mode);
	nlm_recompute_share(share);
	return nlm_granted;
}

/**
 * nlmsvc_unshare_file - delete a share
 * @host: Network client peer
 * @file: File to be unshared
 * @oh: Share owner handle
 * @access: Access mode of the SHARE being released
 * @mode: Deny mode of the SHARE being released
 *
 * Returns an NLM status code.
 */
__be32
nlmsvc_unshare_file(struct nlm_host *host, struct nlm_file *file,
		    struct xdr_netobj *oh, u32 access, u32 mode)
{
	struct lockd_share	*share, **shpp;

	if (nlmsvc_file_cannot_lock(file))
		return nlm_lck_denied_nolocks;

	for (shpp = &file->f_shares; (share = *shpp) != NULL;
					shpp = &share->s_next) {
		if (share->s_host == host && nlm_cmp_owner(share, oh)) {
			share->s_access_deny_bmap &= ~LOCKD_FSH_BIT(access, mode);
			nlm_recompute_share(share);
			if (!share->s_access_deny_bmap) {
				*shpp = share->s_next;
				kfree(share);
			}
			return nlm_granted;
		}
	}

	/* X/Open spec says return success even if there was no
	 * corresponding share. */
	return nlm_granted;
}

/*
 * Traverse all shares for a given file, and delete
 * those owned by the given (type of) host
 */
void nlmsvc_traverse_shares(struct nlm_host *host, struct nlm_file *file,
		nlm_host_match_fn_t match)
{
	struct lockd_share	*share, **shpp;

	shpp = &file->f_shares;
	while ((share = *shpp) !=  NULL) {
		if (match(share->s_host, host)) {
			*shpp = share->s_next;
			kfree(share);
			continue;
		}
		shpp = &share->s_next;
	}
}