kernel-ark/fs/afs/mntpt.c
David Howells 00d3b7a453 [AFS]: Add security support.
Add security support to the AFS filesystem.  Kerberos IV tickets are added as
RxRPC keys are added to the session keyring with the klog program.  open() and
other VFS operations then find this ticket with request_key() and either use
it immediately (eg: mkdir, unlink) or attach it to a file descriptor (open).

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-26 15:57:07 -07:00

297 lines
6.8 KiB
C

/* mountpoint management
*
* Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/mnt_namespace.h>
#include "internal.h"
static struct dentry *afs_mntpt_lookup(struct inode *dir,
struct dentry *dentry,
struct nameidata *nd);
static int afs_mntpt_open(struct inode *inode, struct file *file);
static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);
static void afs_mntpt_expiry_timed_out(struct work_struct *work);
const struct file_operations afs_mntpt_file_operations = {
.open = afs_mntpt_open,
};
const struct inode_operations afs_mntpt_inode_operations = {
.lookup = afs_mntpt_lookup,
.follow_link = afs_mntpt_follow_link,
.readlink = page_readlink,
.getattr = afs_inode_getattr,
};
static LIST_HEAD(afs_vfsmounts);
static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
unsigned long afs_mntpt_expiry_timeout = 10 * 60;
/*
* check a symbolic link to see whether it actually encodes a mountpoint
* - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
*/
int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
{
struct file file = {
.private_data = key,
};
struct page *page;
size_t size;
char *buf;
int ret;
_enter("{%u,%u}", vnode->fid.vnode, vnode->fid.unique);
/* read the contents of the symlink into the pagecache */
page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, &file);
if (IS_ERR(page)) {
ret = PTR_ERR(page);
goto out;
}
ret = -EIO;
wait_on_page_locked(page);
buf = kmap(page);
if (!PageUptodate(page))
goto out_free;
if (PageError(page))
goto out_free;
/* examine the symlink's contents */
size = vnode->status.size;
_debug("symlink to %*.*s", (int) size, (int) size, buf);
if (size > 2 &&
(buf[0] == '%' || buf[0] == '#') &&
buf[size - 1] == '.'
) {
_debug("symlink is a mountpoint");
spin_lock(&vnode->lock);
set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
spin_unlock(&vnode->lock);
}
ret = 0;
out_free:
kunmap(page);
page_cache_release(page);
out:
_leave(" = %d", ret);
return ret;
}
/*
* no valid lookup procedure on this sort of dir
*/
static struct dentry *afs_mntpt_lookup(struct inode *dir,
struct dentry *dentry,
struct nameidata *nd)
{
_enter("%p,%p{%p{%s},%s}",
dir,
dentry,
dentry->d_parent,
dentry->d_parent ?
dentry->d_parent->d_name.name : (const unsigned char *) "",
dentry->d_name.name);
return ERR_PTR(-EREMOTE);
}
/*
* no valid open procedure on this sort of dir
*/
static int afs_mntpt_open(struct inode *inode, struct file *file)
{
_enter("%p,%p{%p{%s},%s}",
inode, file,
file->f_path.dentry->d_parent,
file->f_path.dentry->d_parent ?
file->f_path.dentry->d_parent->d_name.name :
(const unsigned char *) "",
file->f_path.dentry->d_name.name);
return -EREMOTE;
}
/*
* create a vfsmount to be automounted
*/
static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
{
struct afs_super_info *super;
struct vfsmount *mnt;
struct page *page = NULL;
size_t size;
char *buf, *devname = NULL, *options = NULL;
int ret;
_enter("{%s}", mntpt->d_name.name);
BUG_ON(!mntpt->d_inode);
ret = -EINVAL;
size = mntpt->d_inode->i_size;
if (size > PAGE_SIZE - 1)
goto error;
ret = -ENOMEM;
devname = (char *) get_zeroed_page(GFP_KERNEL);
if (!devname)
goto error;
options = (char *) get_zeroed_page(GFP_KERNEL);
if (!options)
goto error;
/* read the contents of the AFS special symlink */
page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
if (IS_ERR(page)) {
ret = PTR_ERR(page);
goto error;
}
ret = -EIO;
wait_on_page_locked(page);
if (!PageUptodate(page) || PageError(page))
goto error;
buf = kmap(page);
memcpy(devname, buf, size);
kunmap(page);
page_cache_release(page);
page = NULL;
/* work out what options we want */
super = AFS_FS_S(mntpt->d_sb);
memcpy(options, "cell=", 5);
strcpy(options + 5, super->volume->cell->name);
if (super->volume->type == AFSVL_RWVOL)
strcat(options, ",rwpath");
/* try and do the mount */
_debug("--- attempting mount %s -o %s ---", devname, options);
mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
_debug("--- mount result %p ---", mnt);
free_page((unsigned long) devname);
free_page((unsigned long) options);
_leave(" = %p", mnt);
return mnt;
error:
if (page)
page_cache_release(page);
if (devname)
free_page((unsigned long) devname);
if (options)
free_page((unsigned long) options);
_leave(" = %d", ret);
return ERR_PTR(ret);
}
/*
* follow a link from a mountpoint directory, thus causing it to be mounted
*/
static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
{
struct vfsmount *newmnt;
int err;
_enter("%p{%s},{%s:%p{%s},}",
dentry,
dentry->d_name.name,
nd->mnt->mnt_devname,
dentry,
nd->dentry->d_name.name);
dput(nd->dentry);
nd->dentry = dget(dentry);
newmnt = afs_mntpt_do_automount(nd->dentry);
if (IS_ERR(newmnt)) {
path_release(nd);
return (void *)newmnt;
}
mntget(newmnt);
err = do_add_mount(newmnt, nd, MNT_SHRINKABLE, &afs_vfsmounts);
switch (err) {
case 0:
mntput(nd->mnt);
dput(nd->dentry);
nd->mnt = newmnt;
nd->dentry = dget(newmnt->mnt_root);
schedule_delayed_work(&afs_mntpt_expiry_timer,
afs_mntpt_expiry_timeout * HZ);
break;
case -EBUSY:
/* someone else made a mount here whilst we were busy */
while (d_mountpoint(nd->dentry) &&
follow_down(&nd->mnt, &nd->dentry))
;
err = 0;
default:
mntput(newmnt);
break;
}
_leave(" = %d", err);
return ERR_PTR(err);
}
/*
* handle mountpoint expiry timer going off
*/
static void afs_mntpt_expiry_timed_out(struct work_struct *work)
{
_enter("");
if (!list_empty(&afs_vfsmounts)) {
mark_mounts_for_expiry(&afs_vfsmounts);
schedule_delayed_work(&afs_mntpt_expiry_timer,
afs_mntpt_expiry_timeout * HZ);
}
_leave("");
}
/*
* kill the AFS mountpoint timer if it's still running
*/
void afs_mntpt_kill_timer(void)
{
_enter("");
ASSERT(list_empty(&afs_vfsmounts));
cancel_delayed_work(&afs_mntpt_expiry_timer);
flush_scheduled_work();
}
/*
* begin unmount by attempting to remove all automounted mountpoints we added
*/
void afs_umount_begin(struct vfsmount *vfsmnt, int flags)
{
shrink_submounts(vfsmnt, &afs_vfsmounts);
}