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![Kees Cook](/assets/img/avatar_default.png)
When the call to nfs_devname() fails, the error path attempts to retain the error via the mnt variable, but this requires a cast across very different types (char * to struct vfsmount *), which the upcoming structure layout randomization plugin flags as being potentially dangerous in the face of randomization. This is a false positive, but what this code actually wants to do is retain the error value, so this patch explicitly sets it, instead of using what seems to be an unexpected cast. Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Trond Myklebust <trond.myklebust@primarydata.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
272 lines
6.9 KiB
C
272 lines
6.9 KiB
C
/*
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* linux/fs/nfs/namespace.c
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*
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* Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
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* - Modified by David Howells <dhowells@redhat.com>
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*
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* NFS namespace
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*/
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#include <linux/module.h>
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#include <linux/dcache.h>
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#include <linux/gfp.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/nfs_fs.h>
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#include <linux/string.h>
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#include <linux/sunrpc/clnt.h>
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#include <linux/vfs.h>
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#include <linux/sunrpc/gss_api.h>
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#include "internal.h"
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#define NFSDBG_FACILITY NFSDBG_VFS
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static void nfs_expire_automounts(struct work_struct *work);
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static LIST_HEAD(nfs_automount_list);
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static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
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int nfs_mountpoint_expiry_timeout = 500 * HZ;
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/*
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* nfs_path - reconstruct the path given an arbitrary dentry
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* @base - used to return pointer to the end of devname part of path
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* @dentry - pointer to dentry
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* @buffer - result buffer
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* @buflen - length of buffer
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* @flags - options (see below)
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*
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* Helper function for constructing the server pathname
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* by arbitrary hashed dentry.
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*
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* This is mainly for use in figuring out the path on the
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* server side when automounting on top of an existing partition
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* and in generating /proc/mounts and friends.
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*
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* Supported flags:
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* NFS_PATH_CANONICAL: ensure there is exactly one slash after
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* the original device (export) name
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* (if unset, the original name is returned verbatim)
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*/
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char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
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unsigned flags)
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{
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char *end;
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int namelen;
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unsigned seq;
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const char *base;
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rename_retry:
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end = buffer+buflen;
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*--end = '\0';
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buflen--;
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seq = read_seqbegin(&rename_lock);
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rcu_read_lock();
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while (1) {
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spin_lock(&dentry->d_lock);
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if (IS_ROOT(dentry))
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break;
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namelen = dentry->d_name.len;
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buflen -= namelen + 1;
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if (buflen < 0)
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goto Elong_unlock;
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end -= namelen;
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memcpy(end, dentry->d_name.name, namelen);
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*--end = '/';
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spin_unlock(&dentry->d_lock);
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dentry = dentry->d_parent;
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}
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if (read_seqretry(&rename_lock, seq)) {
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spin_unlock(&dentry->d_lock);
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rcu_read_unlock();
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goto rename_retry;
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}
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if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
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if (--buflen < 0) {
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spin_unlock(&dentry->d_lock);
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rcu_read_unlock();
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goto Elong;
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}
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*--end = '/';
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}
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*p = end;
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base = dentry->d_fsdata;
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if (!base) {
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spin_unlock(&dentry->d_lock);
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rcu_read_unlock();
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WARN_ON(1);
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return end;
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}
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namelen = strlen(base);
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if (*end == '/') {
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/* Strip off excess slashes in base string */
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while (namelen > 0 && base[namelen - 1] == '/')
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namelen--;
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}
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buflen -= namelen;
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if (buflen < 0) {
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spin_unlock(&dentry->d_lock);
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rcu_read_unlock();
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goto Elong;
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}
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end -= namelen;
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memcpy(end, base, namelen);
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spin_unlock(&dentry->d_lock);
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rcu_read_unlock();
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return end;
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Elong_unlock:
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spin_unlock(&dentry->d_lock);
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rcu_read_unlock();
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if (read_seqretry(&rename_lock, seq))
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goto rename_retry;
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Elong:
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return ERR_PTR(-ENAMETOOLONG);
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}
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EXPORT_SYMBOL_GPL(nfs_path);
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/*
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* nfs_d_automount - Handle crossing a mountpoint on the server
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* @path - The mountpoint
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*
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* When we encounter a mountpoint on the server, we want to set up
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* a mountpoint on the client too, to prevent inode numbers from
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* colliding, and to allow "df" to work properly.
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* On NFSv4, we also want to allow for the fact that different
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* filesystems may be migrated to different servers in a failover
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* situation, and that different filesystems may want to use
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* different security flavours.
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*/
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struct vfsmount *nfs_d_automount(struct path *path)
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{
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struct vfsmount *mnt;
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struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
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struct nfs_fh *fh = NULL;
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struct nfs_fattr *fattr = NULL;
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if (IS_ROOT(path->dentry))
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return ERR_PTR(-ESTALE);
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mnt = ERR_PTR(-ENOMEM);
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fh = nfs_alloc_fhandle();
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fattr = nfs_alloc_fattr();
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if (fh == NULL || fattr == NULL)
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goto out;
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mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
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if (IS_ERR(mnt))
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goto out;
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mntget(mnt); /* prevent immediate expiration */
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mnt_set_expiry(mnt, &nfs_automount_list);
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schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
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out:
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nfs_free_fattr(fattr);
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nfs_free_fhandle(fh);
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return mnt;
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}
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static int
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nfs_namespace_getattr(const struct path *path, struct kstat *stat,
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u32 request_mask, unsigned int query_flags)
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{
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if (NFS_FH(d_inode(path->dentry))->size != 0)
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return nfs_getattr(path, stat, request_mask, query_flags);
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generic_fillattr(d_inode(path->dentry), stat);
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return 0;
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}
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static int
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nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
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{
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if (NFS_FH(d_inode(dentry))->size != 0)
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return nfs_setattr(dentry, attr);
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return -EACCES;
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}
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const struct inode_operations nfs_mountpoint_inode_operations = {
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.getattr = nfs_getattr,
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.setattr = nfs_setattr,
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};
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const struct inode_operations nfs_referral_inode_operations = {
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.getattr = nfs_namespace_getattr,
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.setattr = nfs_namespace_setattr,
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};
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static void nfs_expire_automounts(struct work_struct *work)
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{
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struct list_head *list = &nfs_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(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
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}
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void nfs_release_automount_timer(void)
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{
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if (list_empty(&nfs_automount_list))
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cancel_delayed_work(&nfs_automount_task);
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}
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/*
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* Clone a mountpoint of the appropriate type
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*/
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static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
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const char *devname,
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struct nfs_clone_mount *mountdata)
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{
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return vfs_submount(mountdata->dentry, &nfs_xdev_fs_type, devname, mountdata);
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}
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/**
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* nfs_do_submount - set up mountpoint when crossing a filesystem boundary
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* @dentry - parent directory
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* @fh - filehandle for new root dentry
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* @fattr - attributes for new root inode
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* @authflavor - security flavor to use when performing the mount
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*
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*/
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struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
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struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
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{
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struct nfs_clone_mount mountdata = {
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.sb = dentry->d_sb,
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.dentry = dentry,
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.fh = fh,
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.fattr = fattr,
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.authflavor = authflavor,
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};
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struct vfsmount *mnt;
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char *page = (char *) __get_free_page(GFP_USER);
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char *devname;
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if (page == NULL)
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return ERR_PTR(-ENOMEM);
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devname = nfs_devname(dentry, page, PAGE_SIZE);
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if (IS_ERR(devname))
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mnt = ERR_CAST(devname);
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else
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mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
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free_page((unsigned long)page);
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return mnt;
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}
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EXPORT_SYMBOL_GPL(nfs_do_submount);
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struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
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struct nfs_fh *fh, struct nfs_fattr *fattr)
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{
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int err;
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struct dentry *parent = dget_parent(dentry);
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/* Look it up again to get its attributes */
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err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
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dput(parent);
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if (err != 0)
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return ERR_PTR(err);
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return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
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}
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EXPORT_SYMBOL_GPL(nfs_submount);
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