// SPDX-License-Identifier: GPL-2.0-only
/*
* V9FS FID Management
*
* Copyright (C) 2007 by Latchesar Ionkov <[email protected]>
* Copyright (C) 2005, 2006 by Eric Van Hensbergen <[email protected]>
*/
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>
#include "v9fs.h"
#include "v9fs_vfs.h"
#include "fid.h"
static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
{
hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
}
/**
* v9fs_fid_add - add a fid to a dentry
* @dentry: dentry that the fid is being added to
* @pfid: fid to add, NULLed out
*
*/
void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid)
{
struct p9_fid *fid = *pfid;
spin_lock(&dentry->d_lock);
__add_fid(dentry, fid);
spin_unlock(&dentry->d_lock);
*pfid = NULL;
}
static bool v9fs_is_writeable(int mode)
{
if (mode & (P9_OWRITE|P9_ORDWR))
return true;
else
return false;
}
/**
* v9fs_fid_find_inode - search for an open fid off of the inode list
* @inode: return a fid pointing to a specific inode
* @want_writeable: only consider fids which are writeable
* @uid: return a fid belonging to the specified user
* @any: ignore uid as a selection criteria
*
*/
struct p9_fid *v9fs_fid_find_inode(struct inode *inode, bool want_writeable,
kuid_t uid, bool any)
{
struct hlist_head *h;
struct p9_fid *fid, *ret = NULL;
p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode);
spin_lock(&inode->i_lock);
h = (struct hlist_head *)&inode->i_private;
hlist_for_each_entry(fid, h, ilist) {
if (any || uid_eq(fid->uid, uid)) {
if (want_writeable && !v9fs_is_writeable(fid->mode)) {
p9_debug(P9_DEBUG_VFS, " mode: %x not writeable?\n",
fid->mode);
continue;
}
p9_fid_get(fid);
ret = fid;
break;
}
}
spin_unlock(&inode->i_lock);
return ret;
}
/**
* v9fs_open_fid_add - add an open fid to an inode
* @inode: inode that the fid is being added to
* @pfid: fid to add, NULLed out
*
*/
void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)
{
struct p9_fid *fid = *pfid;
spin_lock(&inode->i_lock);
hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);
spin_unlock(&inode->i_lock);
*pfid = NULL;
}
/**
* v9fs_fid_find - retrieve a fid that belongs to the specified uid
* @dentry: dentry to look for fid in
* @uid: return fid that belongs to the specified user
* @any: if non-zero, return any fid associated with the dentry
*
*/
static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
{
struct p9_fid *fid, *ret;
p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n",
dentry, dentry, from_kuid(&init_user_ns, uid),
any);
ret = NULL;
/* we'll recheck under lock if there's anything to look in */
if (dentry->d_fsdata) {
struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
spin_lock(&dentry->d_lock);
hlist_for_each_entry(fid, h, dlist) {
if (any || uid_eq(fid->uid, uid)) {
ret = fid;
p9_fid_get(ret);
break;
}
}
spin_unlock(&dentry->d_lock);
} else {
if (dentry->d_inode)
ret = v9fs_fid_find_inode(dentry->d_inode, false, uid, any);
}
return ret;
}
/*
* We need to hold v9ses->rename_sem as long as we hold references
* to returned path array. Array element contain pointers to
* dentry names.
*/
static int build_path_from_dentry(struct v9fs_session_info *v9ses,
struct dentry *dentry, const unsigned char ***names)
{
int n = 0, i;
const unsigned char **wnames;
struct dentry *ds;
for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
n++;
wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
if (!wnames)
goto err_out;
for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
wnames[i] = ds->d_name.name;
*names = wnames;
return n;
err_out:
return -ENOMEM;
}
static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
kuid_t uid, int any)
{
struct dentry *ds;
const unsigned char **wnames, *uname;
int i, n, l, access;
struct v9fs_session_info *v9ses;
struct p9_fid *fid, *root_fid, *old_fid;
v9ses = v9fs_dentry2v9ses(dentry);
access = v9ses->flags & V9FS_ACCESS_MASK;
fid = v9fs_fid_find(dentry, uid, any);
if (fid)
return fid;
/*
* we don't have a matching fid. To do a TWALK we need
* parent fid. We need to prevent rename when we want to
* look at the parent.
*/
down_read(&v9ses->rename_sem);
ds = dentry->d_parent;
fid = v9fs_fid_find(ds, uid, any);
if (fid) {
/* Found the parent fid do a lookup with that */
old_fid = fid;
fid = p9_client_walk(old_fid, 1, &dentry->d_name.name, 1);
p9_fid_put(old_fid);
goto fid_out;
}
up_read(&v9ses->rename_sem);
/* start from the root and try to do a lookup */
root_fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
if (!root_fid) {
/* the user is not attached to the fs yet */
if (access == V9FS_ACCESS_SINGLE)
return ERR_PTR(-EPERM);
if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
uname = NULL;
else
uname = v9ses->uname;
fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
v9ses->aname);
if (IS_ERR(fid))
return fid;
root_fid = p9_fid_get(fid);
v9fs_fid_add(dentry->d_sb->s_root, &fid);
}
/* If we are root ourself just return that */
if (dentry->d_sb->s_root == dentry)
return root_fid;
/*
* Do a multipath walk with attached root.
* When walking parent we need to make sure we
* don't have a parallel rename happening
*/
down_read(&v9ses->rename_sem);
n = build_path_from_dentry(v9ses, dentry, &wnames);
if (n < 0) {
fid = ERR_PTR(n);
goto err_out;
}
fid = root_fid;
old_fid = root_fid;
i = 0;
while (i < n) {
l = min(n - i, P9_MAXWELEM);
/*
* We need to hold rename lock when doing a multipath
* walk to ensure none of the path components change
*/
fid = p9_client_walk(old_fid, l, &wnames[i],
old_fid == root_fid /* clone */);
/* non-cloning walk will return the same fid */
if (fid != old_fid) {
p9_fid_put(old_fid);
old_fid = fid;
}
if (IS_ERR(fid)) {
kfree(wnames);
goto err_out;
}
i += l;
}
kfree(wnames);
fid_out:
if (!IS_ERR(fid)) {
spin_lock(&dentry->d_lock);
if (d_unhashed(dentry)) {
spin_unlock(&dentry->d_lock);
p9_fid_put(fid);
fid = ERR_PTR(-ENOENT);
} else {
__add_fid(dentry, fid);
p9_fid_get(fid);
spin_unlock(&dentry->d_lock);
}
}
err_out:
up_read(&v9ses->rename_sem);
return fid;
}
/**
* v9fs_fid_lookup - lookup for a fid, try to walk if not found
* @dentry: dentry to look for fid in
*
* Look for a fid in the specified dentry for the current user.
* If no fid is found, try to create one walking from a fid from the parent
* dentry (if it has one), or the root dentry. If the user haven't accessed
* the fs yet, attach now and walk from the root.
*/
struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
{
kuid_t uid;
int any, access;
struct v9fs_session_info *v9ses;
v9ses = v9fs_dentry2v9ses(dentry);
access = v9ses->flags & V9FS_ACCESS_MASK;
switch (access) {
case V9FS_ACCESS_SINGLE:
case V9FS_ACCESS_USER:
case V9FS_ACCESS_CLIENT:
uid = current_fsuid();
any = 0;
break;
case V9FS_ACCESS_ANY:
uid = v9ses->uid;
any = 1;
break;
default:
uid = INVALID_UID;
any = 0;
break;
}
return v9fs_fid_lookup_with_uid(dentry, uid, any);
}
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