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