fs/sdcardfs/main.c

   1 /*
   2  * fs/sdcardfs/main.c
   3  *
   4  * Copyright (c) 2013 Samsung Electronics Co. Ltd
   5  *   Authors: Daeho Jeong, Woojoong Lee, Seunghwan Hyun,
   6  *               Sunghwan Yun, Sungjong Seo
   7  *
   8  * This program has been developed as a stackable file system based on
   9  * the WrapFS which written by
  10  *
  11  * Copyright (c) 1998-2011 Erez Zadok
  12  * Copyright (c) 2009     Shrikar Archak
  13  * Copyright (c) 2003-2011 Stony Brook University
  14  * Copyright (c) 2003-2011 The Research Foundation of SUNY
  15  *
  16  * This file is dual licensed.  It may be redistributed and/or modified
  17  * under the terms of the Apache 2.0 License OR version 2 of the GNU
  18  * General Public License.
  19  */
  20
  21 #include "sdcardfs.h"
  22 #include <linux/module.h>
  23 #include <linux/types.h>
  24 #include <linux/parser.h>
  25
  26 enum {
  27         Opt_uid,
  28         Opt_gid,
  29         Opt_wgid,
  30         Opt_debug,
  31         Opt_split,
  32         Opt_derive,
  33         Opt_lower_fs,
  34         Opt_reserved_mb,
  35         Opt_err,
  36 };
  37
  38 static const match_table_t sdcardfs_tokens = {
  39         {Opt_uid, "uid=%u"},
  40         {Opt_gid, "gid=%u"},
  41         {Opt_wgid, "wgid=%u"},
  42         {Opt_debug, "debug"},
  43         {Opt_split, "split"},
  44         {Opt_derive, "derive=%s"},
  45         {Opt_lower_fs, "lower_fs=%s"},
  46         {Opt_reserved_mb, "reserved_mb=%u"},
  47         {Opt_err, NULL}
  48 };
  49
  50 static int parse_options(struct super_block *sb, char *options, int silent,
  51                                 int *debug, struct sdcardfs_mount_options *opts)
  52 {
  53         char *p;
  54         substring_t args[MAX_OPT_ARGS];
  55         int option;
  56         char *string_option;
  57
  58         /* by default, we use AID_MEDIA_RW as uid, gid */
  59         opts->fs_low_uid = AID_MEDIA_RW;
  60         opts->fs_low_gid = AID_MEDIA_RW;
  61         /* by default, we use AID_SDCARD_RW as write_gid */
  62         opts->write_gid = AID_SDCARD_RW;
  63         /* default permission policy
  64          * (DERIVE_NONE | DERIVE_LEGACY | DERIVE_UNIFIED) */
  65         opts->derive = DERIVE_NONE;
  66         opts->split_perms = 0;
  67         /* by default, we use LOWER_FS_EXT4 as lower fs type */
  68         opts->lower_fs = LOWER_FS_EXT4;
  69         /* by default, 0MB is reserved */
  70         opts->reserved_mb = 0;
  71
  72         *debug = 0;
  73
  74         if (!options)
  75                 return 0;
  76
  77         while ((p = strsep(&options, ",")) != NULL) {
  78                 int token;
  79                 if (!*p)
  80                         continue;
  81
  82                 token = match_token(p, sdcardfs_tokens, args);
  83
  84                 switch (token) {
  85                 case Opt_debug:
  86                         *debug = 1;
  87                         break;
  88                 case Opt_uid:
  89                         if (match_int(&args[0], &option))
  90                                 return 0;
  91                         opts->fs_low_uid = option;
  92                         break;
  93                 case Opt_gid:
  94                         if (match_int(&args[0], &option))
  95                                 return 0;
  96                         opts->fs_low_gid = option;
  97                         break;
  98                 case Opt_wgid:
  99                         if (match_int(&args[0], &option))
 100                                 return 0;
 101                         opts->write_gid = option;
 102                         break;
 103                 case Opt_split:
 104                         opts->split_perms=1;
 105                         break;
 106                 case Opt_derive:
 107                         string_option = match_strdup(&args[0]);
 108                         if (!strcmp("none", string_option)) {
 109                                 opts->derive = DERIVE_NONE;
 110                         } else if (!strcmp("legacy", string_option)) {
 111                                 opts->derive = DERIVE_LEGACY;
 112                         } else if (!strcmp("unified", string_option)) {
 113                                 opts->derive = DERIVE_UNIFIED;
 114                         } else {
 115                                 kfree(string_option);
 116                                 goto invalid_option;
 117                         }
 118                         kfree(string_option);
 119                         break;
 120                 case Opt_lower_fs:
 121                         string_option = match_strdup(&args[0]);
 122                         if (!strcmp("ext4", string_option)) {
 123                                 opts->lower_fs = LOWER_FS_EXT4;
 124                         } else if (!strcmp("fat", string_option)) {
 125                                 opts->lower_fs = LOWER_FS_FAT;
 126                         } else {
 127                                 kfree(string_option);
 128                                 goto invalid_option;
 129                         }
 130                         kfree(string_option);
 131                         break;
 132                 case Opt_reserved_mb:
 133                         if (match_int(&args[0], &option))
 134                                 return 0;
 135                         opts->reserved_mb = option;
 136                         break;
 137                 /* unknown option */
 138                 default:
 139 invalid_option:
 140                         if (!silent) {
 141                                 printk( KERN_ERR "Unrecognized mount option \"%s\" "
 142                                                 "or missing value", p);
 143                         }
 144                         return -EINVAL;
 145                 }
 146         }
 147
 148         if (*debug) {
 149                 printk( KERN_INFO "sdcardfs : options - debug:%d\n", *debug);
 150                 printk( KERN_INFO "sdcardfs : options - uid:%d\n",
 151                                                         opts->fs_low_uid);
 152                 printk( KERN_INFO "sdcardfs : options - gid:%d\n",
 153                                                         opts->fs_low_gid);
 154         }
 155
 156         return 0;
 157 }
 158
 159 /*
 160  * our custom d_alloc_root work-alike
 161  *
 162  * we can't use d_alloc_root if we want to use our own interpose function
 163  * unchanged, so we simply call our own "fake" d_alloc_root
 164  */
 165 static struct dentry *sdcardfs_d_alloc_root(struct super_block *sb)
 166 {
 167         struct dentry *ret = NULL;
 168
 169         if (sb) {
 170                 static const struct qstr name = {
 171                         .name = "/",
 172                         .len = 1
 173                 };
 174
 175                 ret = d_alloc(NULL, &name);
 176                 if (ret) {
 177                         d_set_d_op(ret, &sdcardfs_ci_dops);
 178                         ret->d_sb = sb;
 179                         ret->d_parent = ret;
 180                 }
 181         }
 182         return ret;
 183 }
 184
 185 /*
 186  * There is no need to lock the sdcardfs_super_info's rwsem as there is no
 187  * way anyone can have a reference to the superblock at this point in time.
 188  */
 189 static int sdcardfs_read_super(struct super_block *sb, const char *dev_name,
 190                                                 void *raw_data, int silent)
 191 {
 192         int err = 0;
 193         int debug;
 194         struct super_block *lower_sb;
 195         struct path lower_path;
 196         struct sdcardfs_sb_info *sb_info;
 197         void *pkgl_id;
 198
 199         printk(KERN_INFO "sdcardfs version 2.0\n");
 200
 201         if (!dev_name) {
 202                 printk(KERN_ERR
 203                        "sdcardfs: read_super: missing dev_name argument\n");
 204                 err = -EINVAL;
 205                 goto out;
 206         }
 207
 208         printk(KERN_INFO "sdcardfs: dev_name -> %s\n", dev_name);
 209         printk(KERN_INFO "sdcardfs: options -> %s\n", (char *)raw_data);
 210
 211         /* parse lower path */
 212         err = kern_path(dev_name, LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
 213                         &lower_path);
 214         if (err) {
 215                 printk(KERN_ERR "sdcardfs: error accessing "
 216                        "lower directory '%s'\n", dev_name);
 217                 goto out;
 218         }
 219
 220         /* allocate superblock private data */
 221         sb->s_fs_info = kzalloc(sizeof(struct sdcardfs_sb_info), GFP_KERNEL);
 222         if (!SDCARDFS_SB(sb)) {
 223                 printk(KERN_CRIT "sdcardfs: read_super: out of memory\n");
 224                 err = -ENOMEM;
 225                 goto out_free;
 226         }
 227
 228         sb_info = sb->s_fs_info;
 229
 230         /* parse options */
 231         err = parse_options(sb, raw_data, silent, &debug, &sb_info->options);
 232         if (err) {
 233                 printk(KERN_ERR "sdcardfs: invalid options\n");
 234                 goto out_freesbi;
 235         }
 236
 237         if (sb_info->options.derive != DERIVE_NONE) {
 238                 pkgl_id = packagelist_create(sb_info->options.write_gid);
 239                 if(IS_ERR(pkgl_id))
 240                         goto out_freesbi;
 241                 else
 242                         sb_info->pkgl_id = pkgl_id;
 243         }
 244
 245         /* set the lower superblock field of upper superblock */
 246         lower_sb = lower_path.dentry->d_sb;
 247         atomic_inc(&lower_sb->s_active);
 248         sdcardfs_set_lower_super(sb, lower_sb);
 249
 250         /* inherit maxbytes from lower file system */
 251         sb->s_maxbytes = lower_sb->s_maxbytes;
 252
 253         /*
 254          * Our c/m/atime granularity is 1 ns because we may stack on file
 255          * systems whose granularity is as good.
 256          */
 257         sb->s_time_gran = 1;
 258
 259         sb->s_magic = SDCARDFS_SUPER_MAGIC;
 260         sb->s_op = &sdcardfs_sops;
 261
 262         /* see comment next to the definition of sdcardfs_d_alloc_root */
 263         sb->s_root = sdcardfs_d_alloc_root(sb);
 264         if (!sb->s_root) {
 265                 err = -ENOMEM;
 266                 goto out_sput;
 267         }
 268
 269         /* link the upper and lower dentries */
 270         sb->s_root->d_fsdata = NULL;
 271         err = new_dentry_private_data(sb->s_root);
 272         if (err)
 273                 goto out_freeroot;
 274
 275         /* set the lower dentries for s_root */
 276         sdcardfs_set_lower_path(sb->s_root, &lower_path);
 277
 278         /* call interpose to create the upper level inode */
 279         err = sdcardfs_interpose(sb->s_root, sb, &lower_path);
 280         if (!err) {
 281                 /* setup permission policy */
 282                 switch(sb_info->options.derive) {
 283                         case DERIVE_NONE:
 284                                 setup_derived_state(sb->s_root->d_inode,
 285                                         PERM_ROOT, 0, AID_ROOT, AID_SDCARD_RW, 00775);
 286                                 sb_info->obbpath_s = NULL;
 287                                 break;
 288                         case DERIVE_LEGACY:
 289                                 /* Legacy behavior used to support internal multiuser layout which
 290                                  * places user_id at the top directory level, with the actual roots
 291                                  * just below that. Shared OBB path is also at top level. */
 292                                 setup_derived_state(sb->s_root->d_inode,
 293                                         PERM_LEGACY_PRE_ROOT, 0, AID_ROOT, AID_SDCARD_R, 00771);
 294                                 /* initialize the obbpath string and lookup the path
 295                                  * sb_info->obb_path will be deactivated by path_put
 296                                  * on sdcardfs_put_super */
 297                                 sb_info->obbpath_s = kzalloc(PATH_MAX, GFP_KERNEL);
 298                                 snprintf(sb_info->obbpath_s, PATH_MAX, "%s/obb", dev_name);
 299                                 err =  prepare_dir(sb_info->obbpath_s,
 300                                                         sb_info->options.fs_low_uid,
 301                                                         sb_info->options.fs_low_gid, 00755);
 302                                 if(err)
 303                                         printk(KERN_ERR "sdcardfs: %s: %d, error on creating %s\n",
 304                                                         __func__,__LINE__, sb_info->obbpath_s);
 305                                 break;
 306                         case DERIVE_UNIFIED:
 307                                 /* Unified multiuser layout which places secondary user_id under
 308                                  * /Android/user and shared OBB path under /Android/obb. */
 309                                 setup_derived_state(sb->s_root->d_inode,
 310                                                 PERM_ROOT, 0, AID_ROOT, AID_SDCARD_R, 00771);
 311
 312                                 sb_info->obbpath_s = kzalloc(PATH_MAX, GFP_KERNEL);
 313                                 snprintf(sb_info->obbpath_s, PATH_MAX, "%s/Android/obb", dev_name);
 314                                 break;
 315                 }
 316                 fix_derived_permission(sb->s_root->d_inode);
 317
 318                 if (!silent)
 319                         printk(KERN_INFO "sdcardfs: mounted on top of %s type %s\n",
 320                                                 dev_name, lower_sb->s_type->name);
 321                 goto out;
 322         }
 323         /* else error: fall through */
 324
 325         free_dentry_private_data(sb->s_root);
 326 out_freeroot:
 327         dput(sb->s_root);
 328 out_sput:
 329         /* drop refs we took earlier */
 330         atomic_dec(&lower_sb->s_active);
 331         packagelist_destroy(sb_info->pkgl_id);
 332 out_freesbi:
 333         kfree(SDCARDFS_SB(sb));
 334         sb->s_fs_info = NULL;
 335 out_free:
 336         path_put(&lower_path);
 337
 338 out:
 339         return err;
 340 }
 341
 342 /* A feature which supports mount_nodev() with options */
 343 static struct dentry *mount_nodev_with_options(struct file_system_type *fs_type,
 344         int flags, const char *dev_name, void *data,
 345         int (*fill_super)(struct super_block *, const char *, void *, int))
 346
 347 {
 348         int error;
 349         struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
 350
 351         if (IS_ERR(s))
 352                 return ERR_CAST(s);
 353
 354         s->s_flags = flags;
 355
 356         error = fill_super(s, dev_name, data, flags & MS_SILENT ? 1 : 0);
 357         if (error) {
 358                 deactivate_locked_super(s);
 359                 return ERR_PTR(error);
 360         }
 361         s->s_flags |= MS_ACTIVE;
 362         return dget(s->s_root);
 363 }
 364
 365 struct dentry *sdcardfs_mount(struct file_system_type *fs_type, int flags,
 366                             const char *dev_name, void *raw_data)
 367 {
 368         /*
 369          * dev_name is a lower_path_name,
 370          * raw_data is a option string.
 371          */
 372         return mount_nodev_with_options(fs_type, flags, dev_name,
 373                                         raw_data, sdcardfs_read_super);
 374 }
 375
 376 static struct file_system_type sdcardfs_fs_type = {
 377         .owner          = THIS_MODULE,
 378         .name           = SDCARDFS_NAME,
 379         .mount          = sdcardfs_mount,
 380         .kill_sb        = generic_shutdown_super,
 381         .fs_flags       = FS_REVAL_DOT,
 382 };
 383
 384 static int __init init_sdcardfs_fs(void)
 385 {
 386         int err;
 387
 388         pr_info("Registering sdcardfs " SDCARDFS_VERSION "\n");
 389
 390         err = sdcardfs_init_inode_cache();
 391         if (err)
 392                 goto out;
 393         err = sdcardfs_init_dentry_cache();
 394         if (err)
 395                 goto out;
 396         err = packagelist_init();
 397         if (err)
 398                 goto out;
 399         err = register_filesystem(&sdcardfs_fs_type);
 400 out:
 401         if (err) {
 402                 sdcardfs_destroy_inode_cache();
 403                 sdcardfs_destroy_dentry_cache();
 404                 packagelist_exit();
 405         }
 406         return err;
 407 }
 408
 409 static void __exit exit_sdcardfs_fs(void)
 410 {
 411         sdcardfs_destroy_inode_cache();
 412         sdcardfs_destroy_dentry_cache();
 413         packagelist_exit();
 414         unregister_filesystem(&sdcardfs_fs_type);
 415         pr_info("Completed sdcardfs module unload\n");
 416 }
 417
 418 MODULE_AUTHOR("Erez Zadok, Filesystems and Storage Lab, Stony Brook University"
 419               " (http://www.fsl.cs.sunysb.edu/)");
 420 MODULE_DESCRIPTION("Wrapfs " SDCARDFS_VERSION
 421                    " (http://wrapfs.filesystems.org/)");
 422 MODULE_LICENSE("GPL");
 423
 424 module_init(init_sdcardfs_fs);
 425 module_exit(exit_sdcardfs_fs);