fs/squashfs/xattr.c

   1 /*
   2  * Squashfs - a compressed read only filesystem for Linux
   3  *
   4  * Copyright (c) 2010
   5  * Phillip Lougher <phillip@squashfs.org.uk>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version 2,
  10  * or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  20  *
  21  * xattr.c
  22  */
  23
  24 #include <linux/init.h>
  25 #include <linux/module.h>
  26 #include <linux/string.h>
  27 #include <linux/fs.h>
  28 #include <linux/vfs.h>
  29 #include <linux/xattr.h>
  30 #include <linux/slab.h>
  31
  32 #include "squashfs_fs.h"
  33 #include "squashfs_fs_sb.h"
  34 #include "squashfs_fs_i.h"
  35 #include "squashfs.h"
  36
  37 static const struct xattr_handler *squashfs_xattr_handler(int);
  38
  39 ssize_t squashfs_listxattr(struct dentry *d, char *buffer,
  40         size_t buffer_size)
  41 {
  42         struct inode *inode = d_inode(d);
  43         struct super_block *sb = inode->i_sb;
  44         struct squashfs_sb_info *msblk = sb->s_fs_info;
  45         u64 start = SQUASHFS_XATTR_BLK(squashfs_i(inode)->xattr)
  46                                                  + msblk->xattr_table;
  47         int offset = SQUASHFS_XATTR_OFFSET(squashfs_i(inode)->xattr);
  48         int count = squashfs_i(inode)->xattr_count;
  49         size_t rest = buffer_size;
  50         int err;
  51
  52         /* check that the file system has xattrs */
  53         if (msblk->xattr_id_table == NULL)
  54                 return -EOPNOTSUPP;
  55
  56         /* loop reading each xattr name */
  57         while (count--) {
  58                 struct squashfs_xattr_entry entry;
  59                 struct squashfs_xattr_val val;
  60                 const struct xattr_handler *handler;
  61                 int name_size, prefix_size = 0;
  62
  63                 err = squashfs_read_metadata(sb, &entry, &start, &offset,
  64                                                         sizeof(entry));
  65                 if (err < 0)
  66                         goto failed;
  67
  68                 name_size = le16_to_cpu(entry.size);
  69                 handler = squashfs_xattr_handler(le16_to_cpu(entry.type));
  70                 if (handler)
  71                         prefix_size = handler->list(handler, d, buffer, rest,
  72                                                     NULL, name_size);
  73                 if (prefix_size) {
  74                         if (buffer) {
  75                                 if (prefix_size + name_size + 1 > rest) {
  76                                         err = -ERANGE;
  77                                         goto failed;
  78                                 }
  79                                 buffer += prefix_size;
  80                         }
  81                         err = squashfs_read_metadata(sb, buffer, &start,
  82                                 &offset, name_size);
  83                         if (err < 0)
  84                                 goto failed;
  85                         if (buffer) {
  86                                 buffer[name_size] = '\0';
  87                                 buffer += name_size + 1;
  88                         }
  89                         rest -= prefix_size + name_size + 1;
  90                 } else  {
  91                         /* no handler or insuffficient privileges, so skip */
  92                         err = squashfs_read_metadata(sb, NULL, &start,
  93                                 &offset, name_size);
  94                         if (err < 0)
  95                                 goto failed;
  96                 }
  97
  98
  99                 /* skip remaining xattr entry */
 100                 err = squashfs_read_metadata(sb, &val, &start, &offset,
 101                                                 sizeof(val));
 102                 if (err < 0)
 103                         goto failed;
 104
 105                 err = squashfs_read_metadata(sb, NULL, &start, &offset,
 106                                                 le32_to_cpu(val.vsize));
 107                 if (err < 0)
 108                         goto failed;
 109         }
 110         err = buffer_size - rest;
 111
 112 failed:
 113         return err;
 114 }
 115
 116
 117 static int squashfs_xattr_get(struct inode *inode, int name_index,
 118         const char *name, void *buffer, size_t buffer_size)
 119 {
 120         struct super_block *sb = inode->i_sb;
 121         struct squashfs_sb_info *msblk = sb->s_fs_info;
 122         u64 start = SQUASHFS_XATTR_BLK(squashfs_i(inode)->xattr)
 123                                                  + msblk->xattr_table;
 124         int offset = SQUASHFS_XATTR_OFFSET(squashfs_i(inode)->xattr);
 125         int count = squashfs_i(inode)->xattr_count;
 126         int name_len = strlen(name);
 127         int err, vsize;
 128         char *target = kmalloc(name_len, GFP_KERNEL);
 129
 130         if (target == NULL)
 131                 return  -ENOMEM;
 132
 133         /* loop reading each xattr name */
 134         for (; count; count--) {
 135                 struct squashfs_xattr_entry entry;
 136                 struct squashfs_xattr_val val;
 137                 int type, prefix, name_size;
 138
 139                 err = squashfs_read_metadata(sb, &entry, &start, &offset,
 140                                                         sizeof(entry));
 141                 if (err < 0)
 142                         goto failed;
 143
 144                 name_size = le16_to_cpu(entry.size);
 145                 type = le16_to_cpu(entry.type);
 146                 prefix = type & SQUASHFS_XATTR_PREFIX_MASK;
 147
 148                 if (prefix == name_index && name_size == name_len)
 149                         err = squashfs_read_metadata(sb, target, &start,
 150                                                 &offset, name_size);
 151                 else
 152                         err = squashfs_read_metadata(sb, NULL, &start,
 153                                                 &offset, name_size);
 154                 if (err < 0)
 155                         goto failed;
 156
 157                 if (prefix == name_index && name_size == name_len &&
 158                                         strncmp(target, name, name_size) == 0) {
 159                         /* found xattr */
 160                         if (type & SQUASHFS_XATTR_VALUE_OOL) {
 161                                 __le64 xattr_val;
 162                                 u64 xattr;
 163                                 /* val is a reference to the real location */
 164                                 err = squashfs_read_metadata(sb, &val, &start,
 165                                                 &offset, sizeof(val));
 166                                 if (err < 0)
 167                                         goto failed;
 168                                 err = squashfs_read_metadata(sb, &xattr_val,
 169                                         &start, &offset, sizeof(xattr_val));
 170                                 if (err < 0)
 171                                         goto failed;
 172                                 xattr = le64_to_cpu(xattr_val);
 173                                 start = SQUASHFS_XATTR_BLK(xattr) +
 174                                                         msblk->xattr_table;
 175                                 offset = SQUASHFS_XATTR_OFFSET(xattr);
 176                         }
 177                         /* read xattr value */
 178                         err = squashfs_read_metadata(sb, &val, &start, &offset,
 179                                                         sizeof(val));
 180                         if (err < 0)
 181                                 goto failed;
 182
 183                         vsize = le32_to_cpu(val.vsize);
 184                         if (buffer) {
 185                                 if (vsize > buffer_size) {
 186                                         err = -ERANGE;
 187                                         goto failed;
 188                                 }
 189                                 err = squashfs_read_metadata(sb, buffer, &start,
 190                                          &offset, vsize);
 191                                 if (err < 0)
 192                                         goto failed;
 193                         }
 194                         break;
 195                 }
 196
 197                 /* no match, skip remaining xattr entry */
 198                 err = squashfs_read_metadata(sb, &val, &start, &offset,
 199                                                         sizeof(val));
 200                 if (err < 0)
 201                         goto failed;
 202                 err = squashfs_read_metadata(sb, NULL, &start, &offset,
 203                                                 le32_to_cpu(val.vsize));
 204                 if (err < 0)
 205                         goto failed;
 206         }
 207         err = count ? vsize : -ENODATA;
 208
 209 failed:
 210         kfree(target);
 211         return err;
 212 }
 213
 214
 215 static size_t squashfs_xattr_handler_list(const struct xattr_handler *handler,
 216                                           struct dentry *d, char *list,
 217                                           size_t list_size, const char *name,
 218                                           size_t name_len)
 219 {
 220         int len = strlen(handler->prefix);
 221
 222         if (list && len <= list_size)
 223                 memcpy(list, handler->prefix, len);
 224         return len;
 225 }
 226
 227 static int squashfs_xattr_handler_get(const struct xattr_handler *handler,
 228                                       struct dentry *d, const char *name,
 229                                       void *buffer, size_t size)
 230 {
 231         if (name[0] == '\0')
 232                 return  -EINVAL;
 233
 234         return squashfs_xattr_get(d_inode(d), handler->flags, name,
 235                 buffer, size);
 236 }
 237
 238 /*
 239  * User namespace support
 240  */
 241 static const struct xattr_handler squashfs_xattr_user_handler = {
 242         .prefix = XATTR_USER_PREFIX,
 243         .flags  = SQUASHFS_XATTR_USER,
 244         .list   = squashfs_xattr_handler_list,
 245         .get    = squashfs_xattr_handler_get
 246 };
 247
 248 /*
 249  * Trusted namespace support
 250  */
 251 static size_t squashfs_trusted_xattr_handler_list(const struct xattr_handler *handler,
 252                                                   struct dentry *d, char *list,
 253                                                   size_t list_size, const char *name,
 254                                                   size_t name_len)
 255 {
 256         if (!capable(CAP_SYS_ADMIN))
 257                 return 0;
 258         return squashfs_xattr_handler_list(handler, d, list, list_size, name,
 259                                            name_len);
 260 }
 261
 262 static const struct xattr_handler squashfs_xattr_trusted_handler = {
 263         .prefix = XATTR_TRUSTED_PREFIX,
 264         .flags  = SQUASHFS_XATTR_TRUSTED,
 265         .list   = squashfs_trusted_xattr_handler_list,
 266         .get    = squashfs_xattr_handler_get
 267 };
 268
 269 /*
 270  * Security namespace support
 271  */
 272 static const struct xattr_handler squashfs_xattr_security_handler = {
 273         .prefix = XATTR_SECURITY_PREFIX,
 274         .flags  = SQUASHFS_XATTR_SECURITY,
 275         .list   = squashfs_xattr_handler_list,
 276         .get    = squashfs_xattr_handler_get
 277 };
 278
 279 static const struct xattr_handler *squashfs_xattr_handler(int type)
 280 {
 281         if (type & ~(SQUASHFS_XATTR_PREFIX_MASK | SQUASHFS_XATTR_VALUE_OOL))
 282                 /* ignore unrecognised type */
 283                 return NULL;
 284
 285         switch (type & SQUASHFS_XATTR_PREFIX_MASK) {
 286         case SQUASHFS_XATTR_USER:
 287                 return &squashfs_xattr_user_handler;
 288         case SQUASHFS_XATTR_TRUSTED:
 289                 return &squashfs_xattr_trusted_handler;
 290         case SQUASHFS_XATTR_SECURITY:
 291                 return &squashfs_xattr_security_handler;
 292         default:
 293                 /* ignore unrecognised type */
 294                 return NULL;
 295         }
 296 }
 297
 298 const struct xattr_handler *squashfs_xattr_handlers[] = {
 299         &squashfs_xattr_user_handler,
 300         &squashfs_xattr_trusted_handler,
 301         &squashfs_xattr_security_handler,
 302         NULL
 303 };
 304