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// 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 "dfs.h"
#include "fs_context.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.
*/
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;
}
static int set_dest_addr(struct smb3_fs_context *ctx, const char *full_path)
{
struct sockaddr *addr = (struct sockaddr *)&ctx->dstaddr;
int rc;
rc = dns_resolve_server_name_to_ip(full_path, addr, NULL);
if (!rc)
cifs_set_port(addr, ctx->port);
return rc;
}
/*
* Create a vfsmount that we can automount
*/
static struct vfsmount *cifs_dfs_do_automount(struct path *path)
{
int rc;
struct dentry *mntpt = path->dentry;
struct fs_context *fc;
struct cifs_sb_info *cifs_sb;
void *page = NULL;
struct smb3_fs_context *ctx, *cur_ctx;
struct smb3_fs_context tmp;
char *full_path;
struct vfsmount *mnt;
if (IS_ROOT(mntpt))
return ERR_PTR(-ESTALE);
/*
* 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.
*/
cifs_sb = CIFS_SB(mntpt->d_sb);
if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
return ERR_PTR(-EREMOTE);
cur_ctx = cifs_sb->ctx;
fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, mntpt);
if (IS_ERR(fc))
return ERR_CAST(fc);
ctx = smb3_fc2context(fc);
page = alloc_dentry_path();
full_path = dfs_get_automount_devname(mntpt, page);
if (IS_ERR(full_path)) {
mnt = ERR_CAST(full_path);
goto out;
}
cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
tmp = *cur_ctx;
tmp.source = full_path;
tmp.leaf_fullpath = NULL;
tmp.UNC = tmp.prepath = NULL;
tmp.dfs_root_ses = NULL;
rc = smb3_fs_context_dup(ctx, &tmp);
if (rc) {
mnt = ERR_PTR(rc);
goto out;
}
rc = set_dest_addr(ctx, full_path);
if (rc) {
mnt = ERR_PTR(rc);
goto out;
}
rc = smb3_parse_devname(full_path, ctx);
if (!rc)
mnt = fc_mount(fc);
else
mnt = ERR_PTR(rc);
out:
put_fs_context(fc);
free_dentry_path(page);
return mnt;
}
/*
* Attempt to automount the referral
*/
struct vfsmount *cifs_dfs_d_automount(struct path *path)
{
struct vfsmount *newmnt;
cifs_dbg(FYI, "%s: %pd\n", __func__, path->dentry);
newmnt = cifs_dfs_do_automount(path);
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 = {
};
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