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         }
 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 references
 143  * to returned path array. Array element contain pointers to
 144  * dentry names.
 145  */
 146 static 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;
 165 err_out:
 166         return -ENOMEM;
 167 }
 168
 169 static 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 need
 185          * parent fid. We need to prevent rename when we want to
 186          * 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                 else
 211                         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 we
 228          * don't have a parallel rename happening
 229          */
 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 multipath
 243                  * walk to ensure none of the path components change
 244                  */
 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);
 259 fid_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         }
 272 err_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 found
 279  * @dentry: dentry to look for fid in
 280  *
 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 parent
 283  * dentry (if it has one), or the root dentry. If the user haven't accessed
 284  * the fs yet, attach now and walk from the root.
 285  */
 286
 287 struct 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