cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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fid.c (7512B)


      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * V9FS FID Management
      4 *
      5 *  Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
      6 *  Copyright (C) 2005, 2006 by Eric Van Hensbergen <ericvh@gmail.com>
      7 */
      8
      9#include <linux/module.h>
     10#include <linux/errno.h>
     11#include <linux/fs.h>
     12#include <linux/slab.h>
     13#include <linux/sched.h>
     14#include <linux/idr.h>
     15#include <net/9p/9p.h>
     16#include <net/9p/client.h>
     17
     18#include "v9fs.h"
     19#include "v9fs_vfs.h"
     20#include "fid.h"
     21
     22static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)
     23{
     24	hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);
     25}
     26
     27
     28/**
     29 * v9fs_fid_add - add a fid to a dentry
     30 * @dentry: dentry that the fid is being added to
     31 * @fid: fid to add
     32 *
     33 */
     34void v9fs_fid_add(struct dentry *dentry, struct p9_fid *fid)
     35{
     36	spin_lock(&dentry->d_lock);
     37	__add_fid(dentry, fid);
     38	spin_unlock(&dentry->d_lock);
     39}
     40
     41/**
     42 * v9fs_fid_find_inode - search for an open fid off of the inode list
     43 * @inode: return a fid pointing to a specific inode
     44 * @uid: return a fid belonging to the specified user
     45 *
     46 */
     47
     48static struct p9_fid *v9fs_fid_find_inode(struct inode *inode, kuid_t uid)
     49{
     50	struct hlist_head *h;
     51	struct p9_fid *fid, *ret = NULL;
     52
     53	p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode);
     54
     55	spin_lock(&inode->i_lock);
     56	h = (struct hlist_head *)&inode->i_private;
     57	hlist_for_each_entry(fid, h, ilist) {
     58		if (uid_eq(fid->uid, uid)) {
     59			refcount_inc(&fid->count);
     60			ret = fid;
     61			break;
     62		}
     63	}
     64	spin_unlock(&inode->i_lock);
     65	return ret;
     66}
     67
     68/**
     69 * v9fs_open_fid_add - add an open fid to an inode
     70 * @inode: inode that the fid is being added to
     71 * @fid: fid to add
     72 *
     73 */
     74
     75void v9fs_open_fid_add(struct inode *inode, struct p9_fid *fid)
     76{
     77	spin_lock(&inode->i_lock);
     78	hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);
     79	spin_unlock(&inode->i_lock);
     80}
     81
     82
     83/**
     84 * v9fs_fid_find - retrieve a fid that belongs to the specified uid
     85 * @dentry: dentry to look for fid in
     86 * @uid: return fid that belongs to the specified user
     87 * @any: if non-zero, return any fid associated with the dentry
     88 *
     89 */
     90
     91static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)
     92{
     93	struct p9_fid *fid, *ret;
     94
     95	p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n",
     96		 dentry, dentry, from_kuid(&init_user_ns, uid),
     97		 any);
     98	ret = NULL;
     99	/* we'll recheck under lock if there's anything to look in */
    100	if (dentry->d_fsdata) {
    101		struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;
    102
    103		spin_lock(&dentry->d_lock);
    104		hlist_for_each_entry(fid, h, dlist) {
    105			if (any || uid_eq(fid->uid, uid)) {
    106				ret = fid;
    107				refcount_inc(&ret->count);
    108				break;
    109			}
    110		}
    111		spin_unlock(&dentry->d_lock);
    112	} else {
    113		if (dentry->d_inode)
    114			ret = v9fs_fid_find_inode(dentry->d_inode, uid);
    115	}
    116
    117	return ret;
    118}
    119
    120/*
    121 * We need to hold v9ses->rename_sem as long as we hold references
    122 * to returned path array. Array element contain pointers to
    123 * dentry names.
    124 */
    125static int build_path_from_dentry(struct v9fs_session_info *v9ses,
    126				  struct dentry *dentry, const unsigned char ***names)
    127{
    128	int n = 0, i;
    129	const unsigned char **wnames;
    130	struct dentry *ds;
    131
    132	for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
    133		n++;
    134
    135	wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
    136	if (!wnames)
    137		goto err_out;
    138
    139	for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
    140		wnames[i] = ds->d_name.name;
    141
    142	*names = wnames;
    143	return n;
    144err_out:
    145	return -ENOMEM;
    146}
    147
    148static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
    149					       kuid_t uid, int any)
    150{
    151	struct dentry *ds;
    152	const unsigned char **wnames, *uname;
    153	int i, n, l, clone, access;
    154	struct v9fs_session_info *v9ses;
    155	struct p9_fid *fid, *old_fid;
    156
    157	v9ses = v9fs_dentry2v9ses(dentry);
    158	access = v9ses->flags & V9FS_ACCESS_MASK;
    159	fid = v9fs_fid_find(dentry, uid, any);
    160	if (fid)
    161		return fid;
    162	/*
    163	 * we don't have a matching fid. To do a TWALK we need
    164	 * parent fid. We need to prevent rename when we want to
    165	 * look at the parent.
    166	 */
    167	down_read(&v9ses->rename_sem);
    168	ds = dentry->d_parent;
    169	fid = v9fs_fid_find(ds, uid, any);
    170	if (fid) {
    171		/* Found the parent fid do a lookup with that */
    172		struct p9_fid *ofid = fid;
    173
    174		fid = p9_client_walk(ofid, 1, &dentry->d_name.name, 1);
    175		p9_client_clunk(ofid);
    176		goto fid_out;
    177	}
    178	up_read(&v9ses->rename_sem);
    179
    180	/* start from the root and try to do a lookup */
    181	fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
    182	if (!fid) {
    183		/* the user is not attached to the fs yet */
    184		if (access == V9FS_ACCESS_SINGLE)
    185			return ERR_PTR(-EPERM);
    186
    187		if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
    188			uname = NULL;
    189		else
    190			uname = v9ses->uname;
    191
    192		fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
    193				       v9ses->aname);
    194		if (IS_ERR(fid))
    195			return fid;
    196
    197		refcount_inc(&fid->count);
    198		v9fs_fid_add(dentry->d_sb->s_root, fid);
    199	}
    200	/* If we are root ourself just return that */
    201	if (dentry->d_sb->s_root == dentry)
    202		return fid;
    203	/*
    204	 * Do a multipath walk with attached root.
    205	 * When walking parent we need to make sure we
    206	 * don't have a parallel rename happening
    207	 */
    208	down_read(&v9ses->rename_sem);
    209	n  = build_path_from_dentry(v9ses, dentry, &wnames);
    210	if (n < 0) {
    211		fid = ERR_PTR(n);
    212		goto err_out;
    213	}
    214	old_fid = fid;
    215	clone = 1;
    216	i = 0;
    217	while (i < n) {
    218		l = min(n - i, P9_MAXWELEM);
    219		/*
    220		 * We need to hold rename lock when doing a multipath
    221		 * walk to ensure none of the patch component change
    222		 */
    223		fid = p9_client_walk(fid, l, &wnames[i], clone);
    224		/* non-cloning walk will return the same fid */
    225		if (fid != old_fid) {
    226			p9_client_clunk(old_fid);
    227			old_fid = fid;
    228		}
    229		if (IS_ERR(fid)) {
    230			kfree(wnames);
    231			goto err_out;
    232		}
    233		i += l;
    234		clone = 0;
    235	}
    236	kfree(wnames);
    237fid_out:
    238	if (!IS_ERR(fid)) {
    239		spin_lock(&dentry->d_lock);
    240		if (d_unhashed(dentry)) {
    241			spin_unlock(&dentry->d_lock);
    242			p9_client_clunk(fid);
    243			fid = ERR_PTR(-ENOENT);
    244		} else {
    245			__add_fid(dentry, fid);
    246			refcount_inc(&fid->count);
    247			spin_unlock(&dentry->d_lock);
    248		}
    249	}
    250err_out:
    251	up_read(&v9ses->rename_sem);
    252	return fid;
    253}
    254
    255/**
    256 * v9fs_fid_lookup - lookup for a fid, try to walk if not found
    257 * @dentry: dentry to look for fid in
    258 *
    259 * Look for a fid in the specified dentry for the current user.
    260 * If no fid is found, try to create one walking from a fid from the parent
    261 * dentry (if it has one), or the root dentry. If the user haven't accessed
    262 * the fs yet, attach now and walk from the root.
    263 */
    264
    265struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
    266{
    267	kuid_t uid;
    268	int  any, access;
    269	struct v9fs_session_info *v9ses;
    270
    271	v9ses = v9fs_dentry2v9ses(dentry);
    272	access = v9ses->flags & V9FS_ACCESS_MASK;
    273	switch (access) {
    274	case V9FS_ACCESS_SINGLE:
    275	case V9FS_ACCESS_USER:
    276	case V9FS_ACCESS_CLIENT:
    277		uid = current_fsuid();
    278		any = 0;
    279		break;
    280
    281	case V9FS_ACCESS_ANY:
    282		uid = v9ses->uid;
    283		any = 1;
    284		break;
    285
    286	default:
    287		uid = INVALID_UID;
    288		any = 0;
    289		break;
    290	}
    291	return v9fs_fid_lookup_with_uid(dentry, uid, any);
    292}
    293
    294struct p9_fid *v9fs_writeback_fid(struct dentry *dentry)
    295{
    296	int err;
    297	struct p9_fid *fid, *ofid;
    298
    299	ofid = v9fs_fid_lookup_with_uid(dentry, GLOBAL_ROOT_UID, 0);
    300	fid = clone_fid(ofid);
    301	if (IS_ERR(fid))
    302		goto error_out;
    303	p9_client_clunk(ofid);
    304	/*
    305	 * writeback fid will only be used to write back the
    306	 * dirty pages. We always request for the open fid in read-write
    307	 * mode so that a partial page write which result in page
    308	 * read can work.
    309	 */
    310	err = p9_client_open(fid, O_RDWR);
    311	if (err < 0) {
    312		p9_client_clunk(fid);
    313		fid = ERR_PTR(err);
    314		goto error_out;
    315	}
    316error_out:
    317	return fid;
    318}