fs/9p/fid.c

   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 <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
  21 static 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 dentry
  29  * @dentry: dentry that the fid is being added to
  30  * @pfid: fid to add, NULLed out
  31  *
  32  */
  33 void 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
  44 static bool v9fs_is_writeable(int mode)
  45 {
  46         if (mode & (P9_OWRITE|P9_ORDWR))
  47                 return true;
  48         else
  49                 return false;
  50 }
  51
  52 /**
  53  * v9fs_fid_find_inode - search for an open fid off of the inode list
  54  * @inode: return a fid pointing to a specific inode
  55  * @want_writeable: only consider fids which are writeable
  56  * @uid: return a fid belonging to the specified user
  57  * @any: ignore uid as a selection criteria
  58  *
  59  */
  60 struct 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 inode
  88  * @inode: inode that the fid is being added to
  89  * @pfid: fid to add, NULLed out
  90  *
  91  */
  92
  93 void 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 uid
 107  * @dentry: dentry to look for fid in
 108  * @uid: return fid that belongs to the specified user
 109  * @any: if non-zero, return any fid associated with the dentry
 110  *
 111  */
 112
 113 static 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         } else {
 135                 if (dentry->d_inode)
 136                         ret = v9fs_fid_find_inode(dentry->d_inode, false, uid, any);
 137         }
 138
 139         return ret;
 140 }
 141
 142 /*
 143  * We need to hold v9ses->rename_sem as long as we hold references
 144  * to returned path array. Array element contain pointers to
 145  * dentry names.
 146  */
 147 static int build_path_from_dentry(struct v9fs_session_info *v9ses,
 148                                   struct dentry *dentry, const unsigned char ***names)
 149 {
 150         int n = 0, i;
 151         const unsigned char **wnames;
 152         struct dentry *ds;
 153
 154         for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
 155                 n++;
 156
 157         wnames = kmalloc_array(n, sizeof(char *), GFP_KERNEL);
 158         if (!wnames)
 159                 goto err_out;
 160
 161         for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
 162                 wnames[i] = ds->d_name.name;
 163
 164         *names = wnames;
 165         return n;
 166 err_out:
 167         return -ENOMEM;
 168 }
 169
 170 static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
 171                                                kuid_t uid, int any)
 172 {
 173         struct dentry *ds;
 174         const unsigned char **wnames, *uname;
 175         int i, n, l, access;
 176         struct v9fs_session_info *v9ses;
 177         struct p9_fid *fid, *root_fid, *old_fid;
 178
 179         v9ses = v9fs_dentry2v9ses(dentry);
 180         access = v9ses->flags & V9FS_ACCESS_MASK;
 181         fid = v9fs_fid_find(dentry, uid, any);
 182         if (fid)
 183                 return fid;
 184         /*
 185          * we don't have a matching fid. To do a TWALK we need
 186          * parent fid. We need to prevent rename when we want to
 187          * look at the parent.
 188          */
 189         down_read(&v9ses->rename_sem);
 190         ds = dentry->d_parent;
 191         fid = v9fs_fid_find(ds, uid, any);
 192         if (fid) {
 193                 /* Found the parent fid do a lookup with that */
 194                 old_fid = fid;
 195
 196                 fid = p9_client_walk(old_fid, 1, &dentry->d_name.name, 1);
 197                 p9_fid_put(old_fid);
 198                 goto fid_out;
 199         }
 200         up_read(&v9ses->rename_sem);
 201
 202         /* start from the root and try to do a lookup */
 203         root_fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
 204         if (!root_fid) {
 205                 /* the user is not attached to the fs yet */
 206                 if (access == V9FS_ACCESS_SINGLE)
 207                         return ERR_PTR(-EPERM);
 208
 209                 if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
 210                         uname = NULL;
 211                 else
 212                         uname = v9ses->uname;
 213
 214                 fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
 215                                        v9ses->aname);
 216                 if (IS_ERR(fid))
 217                         return fid;
 218
 219                 root_fid = p9_fid_get(fid);
 220                 v9fs_fid_add(dentry->d_sb->s_root, &fid);
 221         }
 222         /* If we are root ourself just return that */
 223         if (dentry->d_sb->s_root == dentry)
 224                 return root_fid;
 225
 226         /*
 227          * Do a multipath walk with attached root.
 228          * When walking parent we need to make sure we
 229          * don't have a parallel rename happening
 230          */
 231         down_read(&v9ses->rename_sem);
 232         n  = build_path_from_dentry(v9ses, dentry, &wnames);
 233         if (n < 0) {
 234                 fid = ERR_PTR(n);
 235                 goto err_out;
 236         }
 237         fid = root_fid;
 238         old_fid = root_fid;
 239         i = 0;
 240         while (i < n) {
 241                 l = min(n - i, P9_MAXWELEM);
 242                 /*
 243                  * We need to hold rename lock when doing a multipath
 244                  * walk to ensure none of the path components change
 245                  */
 246                 fid = p9_client_walk(old_fid, l, &wnames[i],
 247                                      old_fid == root_fid /* clone */);
 248                 /* non-cloning walk will return the same fid */
 249                 if (fid != old_fid) {
 250                         p9_fid_put(old_fid);
 251                         old_fid = fid;
 252                 }
 253                 if (IS_ERR(fid)) {
 254                         kfree(wnames);
 255                         goto err_out;
 256                 }
 257                 i += l;
 258         }
 259         kfree(wnames);
 260 fid_out:
 261         if (!IS_ERR(fid)) {
 262                 spin_lock(&dentry->d_lock);
 263                 if (d_unhashed(dentry)) {
 264                         spin_unlock(&dentry->d_lock);
 265                         p9_fid_put(fid);
 266                         fid = ERR_PTR(-ENOENT);
 267                 } else {
 268                         __add_fid(dentry, fid);
 269                         p9_fid_get(fid);
 270                         spin_unlock(&dentry->d_lock);
 271                 }
 272         }
 273 err_out:
 274         up_read(&v9ses->rename_sem);
 275         return fid;
 276 }
 277
 278 /**
 279  * v9fs_fid_lookup - lookup for a fid, try to walk if not found
 280  * @dentry: dentry to look for fid in
 281  *
 282  * Look for a fid in the specified dentry for the current user.
 283  * If no fid is found, try to create one walking from a fid from the parent
 284  * dentry (if it has one), or the root dentry. If the user haven't accessed
 285  * the fs yet, attach now and walk from the root.
 286  */
 287
 288 struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
 289 {
 290         kuid_t uid;
 291         int  any, access;
 292         struct v9fs_session_info *v9ses;
 293
 294         v9ses = v9fs_dentry2v9ses(dentry);
 295         access = v9ses->flags & V9FS_ACCESS_MASK;
 296         switch (access) {
 297         case V9FS_ACCESS_SINGLE:
 298         case V9FS_ACCESS_USER:
 299         case V9FS_ACCESS_CLIENT:
 300                 uid = current_fsuid();
 301                 any = 0;
 302                 break;
 303
 304         case V9FS_ACCESS_ANY:
 305                 uid = v9ses->uid;
 306                 any = 1;
 307                 break;
 308
 309         default:
 310                 uid = INVALID_UID;
 311                 any = 0;
 312                 break;
 313         }
 314         return v9fs_fid_lookup_with_uid(dentry, uid, any);
 315 }
 316