1 files changed, 151 insertions, 0 deletions
diff --git a/fs/lockd/svcshare.c b/fs/lockd/svcshare.c
new file mode 100644
index 000000000..a58b7035b
--- /dev/null
+++ b/fs/lockd/svcshare.c
@@ -0,0 +1,151 @@
+// 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;
+	}
+}