1 files changed, 416 insertions, 0 deletions
diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
new file mode 100644
index 000000000..42125601e
--- /dev/null
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -0,0 +1,416 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Contains the CIFS DFS referral mounting routines used for handling
+ *   traversal via DFS junction point
+ *
+ *   Copyright (c) 2007 Igor Mammedov
+ *   Copyright (C) International Business Machines  Corp., 2008
+ *   Author(s): Igor Mammedov (niallain@gmail.com)
+ *		Steve French (sfrench@us.ibm.com)
+ */
+
+#include <linux/dcache.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/slab.h>
+#include <linux/vfs.h>
+#include <linux/fs.h>
+#include <linux/inet.h>
+#include "cifsglob.h"
+#include "cifsproto.h"
+#include "cifsfs.h"
+#include "dns_resolve.h"
+#include "cifs_debug.h"
+#include "cifs_unicode.h"
+#include "dfs_cache.h"
+
+static LIST_HEAD(cifs_dfs_automount_list);
+
+static void cifs_dfs_expire_automounts(struct work_struct *work);
+static DECLARE_DELAYED_WORK(cifs_dfs_automount_task,
+			    cifs_dfs_expire_automounts);
+static int cifs_dfs_mountpoint_expiry_timeout = 500 * HZ;
+
+static void cifs_dfs_expire_automounts(struct work_struct *work)
+{
+	struct list_head *list = &cifs_dfs_automount_list;
+
+	mark_mounts_for_expiry(list);
+	if (!list_empty(list))
+		schedule_delayed_work(&cifs_dfs_automount_task,
+				      cifs_dfs_mountpoint_expiry_timeout);
+}
+
+void cifs_dfs_release_automount_timer(void)
+{
+	BUG_ON(!list_empty(&cifs_dfs_automount_list));
+	cancel_delayed_work_sync(&cifs_dfs_automount_task);
+}
+
+/**
+ * cifs_build_devname - build a devicename from a UNC and optional prepath
+ * @nodename:	pointer to UNC string
+ * @prepath:	pointer to prefixpath (or NULL if there isn't one)
+ *
+ * Build a new cifs devicename after chasing a DFS referral. Allocate a buffer
+ * big enough to hold the final thing. Copy the UNC from the nodename, and
+ * concatenate the prepath onto the end of it if there is one.
+ *
+ * Returns pointer to the built string, or a ERR_PTR. Caller is responsible
+ * for freeing the returned string.
+ */
+static char *
+cifs_build_devname(char *nodename, const char *prepath)
+{
+	size_t pplen;
+	size_t unclen;
+	char *dev;
+	char *pos;
+
+	/* skip over any preceding delimiters */
+	nodename += strspn(nodename, "\\");
+	if (!*nodename)
+		return ERR_PTR(-EINVAL);
+
+	/* get length of UNC and set pos to last char */
+	unclen = strlen(nodename);
+	pos = nodename + unclen - 1;
+
+	/* trim off any trailing delimiters */
+	while (*pos == '\\') {
+		--pos;
+		--unclen;
+	}
+
+	/* allocate a buffer:
+	 * +2 for preceding "//"
+	 * +1 for delimiter between UNC and prepath
+	 * +1 for trailing NULL
+	 */
+	pplen = prepath ? strlen(prepath) : 0;
+	dev = kmalloc(2 + unclen + 1 + pplen + 1, GFP_KERNEL);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	pos = dev;
+	/* add the initial "//" */
+	*pos = '/';
+	++pos;
+	*pos = '/';
+	++pos;
+
+	/* copy in the UNC portion from referral */
+	memcpy(pos, nodename, unclen);
+	pos += unclen;
+
+	/* copy the prefixpath remainder (if there is one) */
+	if (pplen) {
+		*pos = '/';
+		++pos;
+		memcpy(pos, prepath, pplen);
+		pos += pplen;
+	}
+
+	/* NULL terminator */
+	*pos = '\0';
+
+	convert_delimiter(dev, '/');
+	return dev;
+}
+
+
+/**
+ * cifs_compose_mount_options	-	creates mount options for referral
+ * @sb_mountdata:	parent/root DFS mount options (template)
+ * @fullpath:		full path in UNC format
+ * @ref:		optional server's referral
+ * @devname:		optional pointer for saving device name
+ *
+ * creates mount options for submount based on template options sb_mountdata
+ * and replacing unc,ip,prefixpath options with ones we've got form ref_unc.
+ *
+ * Returns: pointer to new mount options or ERR_PTR.
+ * Caller is responsible for freeing returned value if it is not error.
+ */
+char *cifs_compose_mount_options(const char *sb_mountdata,
+				   const char *fullpath,
+				   const struct dfs_info3_param *ref,
+				   char **devname)
+{
+	int rc;
+	char *name;
+	char *mountdata = NULL;
+	const char *prepath = NULL;
+	int md_len;
+	char *tkn_e;
+	char *srvIP = NULL;
+	char sep = ',';
+	int off, noff;
+
+	if (sb_mountdata == NULL)
+		return ERR_PTR(-EINVAL);
+
+	if (ref) {
+		if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
+			return ERR_PTR(-EINVAL);
+
+		if (strlen(fullpath) - ref->path_consumed) {
+			prepath = fullpath + ref->path_consumed;
+			/* skip initial delimiter */
+			if (*prepath == '/' || *prepath == '\\')
+				prepath++;
+		}
+
+		name = cifs_build_devname(ref->node_name, prepath);
+		if (IS_ERR(name)) {
+			rc = PTR_ERR(name);
+			name = NULL;
+			goto compose_mount_options_err;
+		}
+	} else {
+		name = cifs_build_devname((char *)fullpath, NULL);
+		if (IS_ERR(name)) {
+			rc = PTR_ERR(name);
+			name = NULL;
+			goto compose_mount_options_err;
+		}
+	}
+
+	rc = dns_resolve_server_name_to_ip(name, &srvIP);
+	if (rc < 0) {
+		cifs_dbg(FYI, "%s: Failed to resolve server part of %s to IP: %d\n",
+			 __func__, name, rc);
+		goto compose_mount_options_err;
+	}
+
+	/*
+	 * In most cases, we'll be building a shorter string than the original,
+	 * but we do have to assume that the address in the ip= option may be
+	 * much longer than the original. Add the max length of an address
+	 * string to the length of the original string to allow for worst case.
+	 */
+	md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
+	mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
+	if (mountdata == NULL) {
+		rc = -ENOMEM;
+		goto compose_mount_options_err;
+	}
+
+	/* copy all options except of unc,ip,prefixpath */
+	off = 0;
+	if (strncmp(sb_mountdata, "sep=", 4) == 0) {
+			sep = sb_mountdata[4];
+			strncpy(mountdata, sb_mountdata, 5);
+			off += 5;
+	}
+
+	do {
+		tkn_e = strchr(sb_mountdata + off, sep);
+		if (tkn_e == NULL)
+			noff = strlen(sb_mountdata + off);
+		else
+			noff = tkn_e - (sb_mountdata + off) + 1;
+
+		if (strncasecmp(sb_mountdata + off, "unc=", 4) == 0) {
+			off += noff;
+			continue;
+		}
+		if (strncasecmp(sb_mountdata + off, "ip=", 3) == 0) {
+			off += noff;
+			continue;
+		}
+		if (strncasecmp(sb_mountdata + off, "prefixpath=", 11) == 0) {
+			off += noff;
+			continue;
+		}
+		strncat(mountdata, sb_mountdata + off, noff);
+		off += noff;
+	} while (tkn_e);
+	strcat(mountdata, sb_mountdata + off);
+	mountdata[md_len] = '\0';
+
+	/* copy new IP and ref share name */
+	if (mountdata[strlen(mountdata) - 1] != sep)
+		strncat(mountdata, &sep, 1);
+	strcat(mountdata, "ip=");
+	strcat(mountdata, srvIP);
+
+	if (devname)
+		*devname = name;
+	else
+		kfree(name);
+
+	/*cifs_dbg(FYI, "%s: parent mountdata: %s\n", __func__, sb_mountdata);*/
+	/*cifs_dbg(FYI, "%s: submount mountdata: %s\n", __func__, mountdata );*/
+
+compose_mount_options_out:
+	kfree(srvIP);
+	return mountdata;
+
+compose_mount_options_err:
+	kfree(mountdata);
+	mountdata = ERR_PTR(rc);
+	kfree(name);
+	goto compose_mount_options_out;
+}
+
+/**
+ * cifs_dfs_do_mount - mounts specified path using DFS full path
+ *
+ * Always pass down @fullpath to smb3_do_mount() so we can use the root server
+ * to perform failover in case we failed to connect to the first target in the
+ * referral.
+ *
+ * @cifs_sb:		parent/root superblock
+ * @fullpath:		full path in UNC format
+ */
+static struct vfsmount *cifs_dfs_do_mount(struct dentry *mntpt,
+					  struct cifs_sb_info *cifs_sb,
+					  const char *fullpath)
+{
+	struct vfsmount *mnt;
+	char *mountdata;
+	char *devname;
+
+	devname = kstrndup(fullpath, strlen(fullpath), GFP_KERNEL);
+	if (!devname)
+		return ERR_PTR(-ENOMEM);
+
+	convert_delimiter(devname, '/');
+
+	/* strip first '\' from fullpath */
+	mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
+					       fullpath + 1, NULL, NULL);
+	if (IS_ERR(mountdata)) {
+		kfree(devname);
+		return (struct vfsmount *)mountdata;
+	}
+
+	mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
+	kfree(mountdata);
+	kfree(devname);
+	return mnt;
+}
+
+/*
+ * Create a vfsmount that we can automount
+ */
+static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
+{
+	struct cifs_sb_info *cifs_sb;
+	struct cifs_ses *ses;
+	struct cifs_tcon *tcon;
+	char *full_path, *root_path;
+	unsigned int xid;
+	int rc;
+	struct vfsmount *mnt;
+
+	cifs_dbg(FYI, "in %s\n", __func__);
+	BUG_ON(IS_ROOT(mntpt));
+
+	/*
+	 * The MSDFS spec states that paths in DFS referral requests and
+	 * responses must be prefixed by a single '\' character instead of
+	 * the double backslashes usually used in the UNC. This function
+	 * gives us the latter, so we must adjust the result.
+	 */
+	mnt = ERR_PTR(-ENOMEM);
+
+	cifs_sb = CIFS_SB(mntpt->d_sb);
+	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) {
+		mnt = ERR_PTR(-EREMOTE);
+		goto cdda_exit;
+	}
+
+	/* always use tree name prefix */
+	full_path = build_path_from_dentry_optional_prefix(mntpt, true);
+	if (full_path == NULL)
+		goto cdda_exit;
+
+	convert_delimiter(full_path, '\\');
+
+	cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
+
+	if (!cifs_sb_master_tlink(cifs_sb)) {
+		cifs_dbg(FYI, "%s: master tlink is NULL\n", __func__);
+		goto free_full_path;
+	}
+
+	tcon = cifs_sb_master_tcon(cifs_sb);
+	if (!tcon) {
+		cifs_dbg(FYI, "%s: master tcon is NULL\n", __func__);
+		goto free_full_path;
+	}
+
+	root_path = kstrdup(tcon->treeName, GFP_KERNEL);
+	if (!root_path) {
+		mnt = ERR_PTR(-ENOMEM);
+		goto free_full_path;
+	}
+	cifs_dbg(FYI, "%s: root path: %s\n", __func__, root_path);
+
+	ses = tcon->ses;
+	xid = get_xid();
+
+	/*
+	 * If DFS root has been expired, then unconditionally fetch it again to
+	 * refresh DFS referral cache.
+	 */
+	rc = dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
+			    root_path + 1, NULL, NULL);
+	if (!rc) {
+		rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
+				    cifs_remap(cifs_sb), full_path + 1,
+				    NULL, NULL);
+	}
+
+	free_xid(xid);
+
+	if (rc) {
+		mnt = ERR_PTR(rc);
+		goto free_root_path;
+	}
+	/*
+	 * OK - we were able to get and cache a referral for @full_path.
+	 *
+	 * Now, pass it down to cifs_mount() and it will retry every available
+	 * node server in case of failures - no need to do it here.
+	 */
+	mnt = cifs_dfs_do_mount(mntpt, cifs_sb, full_path);
+	cifs_dbg(FYI, "%s: cifs_dfs_do_mount:%s , mnt:%p\n", __func__,
+		 full_path + 1, mnt);
+
+free_root_path:
+	kfree(root_path);
+free_full_path:
+	kfree(full_path);
+cdda_exit:
+	cifs_dbg(FYI, "leaving %s\n" , __func__);
+	return mnt;
+}
+
+/*
+ * Attempt to automount the referral
+ */
+struct vfsmount *cifs_dfs_d_automount(struct path *path)
+{
+	struct vfsmount *newmnt;
+
+	cifs_dbg(FYI, "in %s\n", __func__);
+
+	newmnt = cifs_dfs_do_automount(path->dentry);
+	if (IS_ERR(newmnt)) {
+		cifs_dbg(FYI, "leaving %s [automount failed]\n" , __func__);
+		return newmnt;
+	}
+
+	mntget(newmnt); /* prevent immediate expiration */
+	mnt_set_expiry(newmnt, &cifs_dfs_automount_list);
+	schedule_delayed_work(&cifs_dfs_automount_task,
+			      cifs_dfs_mountpoint_expiry_timeout);
+	cifs_dbg(FYI, "leaving %s [ok]\n" , __func__);
+	return newmnt;
+}
+
+const struct inode_operations cifs_dfs_referral_inode_operations = {
+};