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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * V9FS FID Management4 *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 <net/9p/9p.h>15#include <net/9p/client.h>16 17#include "v9fs.h"18#include "v9fs_vfs.h"19#include "fid.h"20 21static inline void __add_fid(struct dentry *dentry, struct p9_fid *fid)22{23 hlist_add_head(&fid->dlist, (struct hlist_head *)&dentry->d_fsdata);24}25 26 27/**28 * v9fs_fid_add - add a fid to a dentry29 * @dentry: dentry that the fid is being added to30 * @pfid: fid to add, NULLed out31 *32 */33void v9fs_fid_add(struct dentry *dentry, struct p9_fid **pfid)34{35 struct p9_fid *fid = *pfid;36 37 spin_lock(&dentry->d_lock);38 __add_fid(dentry, fid);39 spin_unlock(&dentry->d_lock);40 41 *pfid = NULL;42}43 44static bool v9fs_is_writeable(int mode)45{46 if (mode & (P9_OWRITE|P9_ORDWR))47 return true;48 else49 return false;50}51 52/**53 * v9fs_fid_find_inode - search for an open fid off of the inode list54 * @inode: return a fid pointing to a specific inode55 * @want_writeable: only consider fids which are writeable56 * @uid: return a fid belonging to the specified user57 * @any: ignore uid as a selection criteria58 *59 */60struct p9_fid *v9fs_fid_find_inode(struct inode *inode, bool want_writeable,61 kuid_t uid, bool any)62{63 struct hlist_head *h;64 struct p9_fid *fid, *ret = NULL;65 66 p9_debug(P9_DEBUG_VFS, " inode: %p\n", inode);67 68 spin_lock(&inode->i_lock);69 h = (struct hlist_head *)&inode->i_private;70 hlist_for_each_entry(fid, h, ilist) {71 if (any || uid_eq(fid->uid, uid)) {72 if (want_writeable && !v9fs_is_writeable(fid->mode)) {73 p9_debug(P9_DEBUG_VFS, " mode: %x not writeable?\n",74 fid->mode);75 continue;76 }77 p9_fid_get(fid);78 ret = fid;79 break;80 }81 }82 spin_unlock(&inode->i_lock);83 return ret;84}85 86/**87 * v9fs_open_fid_add - add an open fid to an inode88 * @inode: inode that the fid is being added to89 * @pfid: fid to add, NULLed out90 *91 */92 93void v9fs_open_fid_add(struct inode *inode, struct p9_fid **pfid)94{95 struct p9_fid *fid = *pfid;96 97 spin_lock(&inode->i_lock);98 hlist_add_head(&fid->ilist, (struct hlist_head *)&inode->i_private);99 spin_unlock(&inode->i_lock);100 101 *pfid = NULL;102}103 104 105/**106 * v9fs_fid_find - retrieve a fid that belongs to the specified uid107 * @dentry: dentry to look for fid in108 * @uid: return fid that belongs to the specified user109 * @any: if non-zero, return any fid associated with the dentry110 *111 */112 113static struct p9_fid *v9fs_fid_find(struct dentry *dentry, kuid_t uid, int any)114{115 struct p9_fid *fid, *ret;116 117 p9_debug(P9_DEBUG_VFS, " dentry: %pd (%p) uid %d any %d\n",118 dentry, dentry, from_kuid(&init_user_ns, uid),119 any);120 ret = NULL;121 /* we'll recheck under lock if there's anything to look in */122 if (dentry->d_fsdata) {123 struct hlist_head *h = (struct hlist_head *)&dentry->d_fsdata;124 125 spin_lock(&dentry->d_lock);126 hlist_for_each_entry(fid, h, dlist) {127 if (any || uid_eq(fid->uid, uid)) {128 ret = fid;129 p9_fid_get(ret);130 break;131 }132 }133 spin_unlock(&dentry->d_lock);134 }135 if (!ret && dentry->d_inode)136 ret = v9fs_fid_find_inode(dentry->d_inode, false, uid, any);137 138 return ret;139}140 141/*142 * We need to hold v9ses->rename_sem as long as we hold references143 * to returned path array. Array element contain pointers to144 * dentry names.145 */146static int build_path_from_dentry(struct v9fs_session_info *v9ses,147 struct dentry *dentry, const unsigned char ***names)148{149 int n = 0, i;150 const unsigned char **wnames;151 struct dentry *ds;152 153 for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)154 n++;155 156 wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);157 if (!wnames)158 goto err_out;159 160 for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)161 wnames[i] = ds->d_name.name;162 163 *names = wnames;164 return n;165err_out:166 return -ENOMEM;167}168 169static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,170 kuid_t uid, int any)171{172 struct dentry *ds;173 const unsigned char **wnames, *uname;174 int i, n, l, access;175 struct v9fs_session_info *v9ses;176 struct p9_fid *fid, *root_fid, *old_fid;177 178 v9ses = v9fs_dentry2v9ses(dentry);179 access = v9ses->flags & V9FS_ACCESS_MASK;180 fid = v9fs_fid_find(dentry, uid, any);181 if (fid)182 return fid;183 /*184 * we don't have a matching fid. To do a TWALK we need185 * parent fid. We need to prevent rename when we want to186 * look at the parent.187 */188 down_read(&v9ses->rename_sem);189 ds = dentry->d_parent;190 fid = v9fs_fid_find(ds, uid, any);191 if (fid) {192 /* Found the parent fid do a lookup with that */193 old_fid = fid;194 195 fid = p9_client_walk(old_fid, 1, &dentry->d_name.name, 1);196 p9_fid_put(old_fid);197 goto fid_out;198 }199 up_read(&v9ses->rename_sem);200 201 /* start from the root and try to do a lookup */202 root_fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);203 if (!root_fid) {204 /* the user is not attached to the fs yet */205 if (access == V9FS_ACCESS_SINGLE)206 return ERR_PTR(-EPERM);207 208 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))209 uname = NULL;210 else211 uname = v9ses->uname;212 213 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,214 v9ses->aname);215 if (IS_ERR(fid))216 return fid;217 218 root_fid = p9_fid_get(fid);219 v9fs_fid_add(dentry->d_sb->s_root, &fid);220 }221 /* If we are root ourself just return that */222 if (dentry->d_sb->s_root == dentry)223 return root_fid;224 225 /*226 * Do a multipath walk with attached root.227 * When walking parent we need to make sure we228 * don't have a parallel rename happening229 */230 down_read(&v9ses->rename_sem);231 n = build_path_from_dentry(v9ses, dentry, &wnames);232 if (n < 0) {233 fid = ERR_PTR(n);234 goto err_out;235 }236 fid = root_fid;237 old_fid = root_fid;238 i = 0;239 while (i < n) {240 l = min(n - i, P9_MAXWELEM);241 /*242 * We need to hold rename lock when doing a multipath243 * walk to ensure none of the path components change244 */245 fid = p9_client_walk(old_fid, l, &wnames[i],246 old_fid == root_fid /* clone */);247 /* non-cloning walk will return the same fid */248 if (fid != old_fid) {249 p9_fid_put(old_fid);250 old_fid = fid;251 }252 if (IS_ERR(fid)) {253 kfree(wnames);254 goto err_out;255 }256 i += l;257 }258 kfree(wnames);259fid_out:260 if (!IS_ERR(fid)) {261 spin_lock(&dentry->d_lock);262 if (d_unhashed(dentry)) {263 spin_unlock(&dentry->d_lock);264 p9_fid_put(fid);265 fid = ERR_PTR(-ENOENT);266 } else {267 __add_fid(dentry, fid);268 p9_fid_get(fid);269 spin_unlock(&dentry->d_lock);270 }271 }272err_out:273 up_read(&v9ses->rename_sem);274 return fid;275}276 277/**278 * v9fs_fid_lookup - lookup for a fid, try to walk if not found279 * @dentry: dentry to look for fid in280 *281 * Look for a fid in the specified dentry for the current user.282 * If no fid is found, try to create one walking from a fid from the parent283 * dentry (if it has one), or the root dentry. If the user haven't accessed284 * the fs yet, attach now and walk from the root.285 */286 287struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)288{289 kuid_t uid;290 int any, access;291 struct v9fs_session_info *v9ses;292 293 v9ses = v9fs_dentry2v9ses(dentry);294 access = v9ses->flags & V9FS_ACCESS_MASK;295 switch (access) {296 case V9FS_ACCESS_SINGLE:297 case V9FS_ACCESS_USER:298 case V9FS_ACCESS_CLIENT:299 uid = current_fsuid();300 any = 0;301 break;302 303 case V9FS_ACCESS_ANY:304 uid = v9ses->uid;305 any = 1;306 break;307 308 default:309 uid = INVALID_UID;310 any = 0;311 break;312 }313 return v9fs_fid_lookup_with_uid(dentry, uid, any);314}315 316