fs/sysfs/inode.c

   1 /*
   2  * fs/sysfs/inode.c - basic sysfs inode and dentry operations
   3  *
   4  * Copyright (c) 2001-3 Patrick Mochel
   5  * Copyright (c) 2007 SUSE Linux Products GmbH
   6  * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
   7  *
   8  * This file is released under the GPLv2.
   9  *
  10  * Please see Documentation/filesystems/sysfs.txt for more information.
  11  */
  12
  13 #undef DEBUG
  14
  15 #include <linux/pagemap.h>
  16 #include <linux/namei.h>
  17 #include <linux/backing-dev.h>
  18 #include <linux/capability.h>
  19 #include <linux/errno.h>
  20 #include <linux/sched.h>
  21 #include <linux/slab.h>
  22 #include <linux/sysfs.h>
  23 #include <linux/xattr.h>
  24 #include <linux/security.h>
  25 #include "sysfs.h"
  26
  27 extern struct super_block * sysfs_sb;
  28
  29 static const struct address_space_operations sysfs_aops = {
  30         .readpage       = simple_readpage,
  31         .write_begin    = simple_write_begin,
  32         .write_end      = simple_write_end,
  33 };
  34
  35 static struct backing_dev_info sysfs_backing_dev_info = {
  36         .name           = "sysfs",
  37         .ra_pages       = 0,    /* No readahead */
  38         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
  39 };
  40
  41 static const struct inode_operations sysfs_inode_operations ={
  42         .permission     = sysfs_permission,
  43         .setattr        = sysfs_setattr,
  44         .getattr        = sysfs_getattr,
  45         .setxattr       = sysfs_setxattr,
  46 };
  47
  48 int __init sysfs_inode_init(void)
  49 {
  50         return bdi_init(&sysfs_backing_dev_info);
  51 }
  52
  53 static struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)
  54 {
  55         struct sysfs_inode_attrs *attrs;
  56         struct iattr *iattrs;
  57
  58         attrs = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
  59         if (!attrs)
  60                 return NULL;
  61         iattrs = &attrs->ia_iattr;
  62
  63         /* assign default attributes */
  64         iattrs->ia_mode = sd->s_mode;
  65         iattrs->ia_uid = 0;
  66         iattrs->ia_gid = 0;
  67         iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
  68
  69         return attrs;
  70 }
  71
  72 int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr * iattr)
  73 {
  74         struct sysfs_inode_attrs *sd_attrs;
  75         struct iattr *iattrs;
  76         unsigned int ia_valid = iattr->ia_valid;
  77
  78         sd_attrs = sd->s_iattr;
  79
  80         if (!sd_attrs) {
  81                 /* setting attributes for the first time, allocate now */
  82                 sd_attrs = sysfs_init_inode_attrs(sd);
  83                 if (!sd_attrs)
  84                         return -ENOMEM;
  85                 sd->s_iattr = sd_attrs;
  86         }
  87         /* attributes were changed at least once in past */
  88         iattrs = &sd_attrs->ia_iattr;
  89
  90         if (ia_valid & ATTR_UID)
  91                 iattrs->ia_uid = iattr->ia_uid;
  92         if (ia_valid & ATTR_GID)
  93                 iattrs->ia_gid = iattr->ia_gid;
  94         if (ia_valid & ATTR_ATIME)
  95                 iattrs->ia_atime = iattr->ia_atime;
  96         if (ia_valid & ATTR_MTIME)
  97                 iattrs->ia_mtime = iattr->ia_mtime;
  98         if (ia_valid & ATTR_CTIME)
  99                 iattrs->ia_ctime = iattr->ia_ctime;
 100         if (ia_valid & ATTR_MODE) {
 101                 umode_t mode = iattr->ia_mode;
 102                 iattrs->ia_mode = sd->s_mode = mode;
 103         }
 104         return 0;
 105 }
 106
 107 int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
 108 {
 109         struct inode *inode = dentry->d_inode;
 110         struct sysfs_dirent *sd = dentry->d_fsdata;
 111         int error;
 112
 113         if (!sd)
 114                 return -EINVAL;
 115
 116         mutex_lock(&sysfs_mutex);
 117         error = inode_change_ok(inode, iattr);
 118         if (error)
 119                 goto out;
 120
 121         error = sysfs_sd_setattr(sd, iattr);
 122         if (error)
 123                 goto out;
 124
 125         /* this ignores size changes */
 126         setattr_copy(inode, iattr);
 127
 128 out:
 129         mutex_unlock(&sysfs_mutex);
 130         return error;
 131 }
 132
 133 static int sysfs_sd_setsecdata(struct sysfs_dirent *sd, void **secdata, u32 *secdata_len)
 134 {
 135         struct sysfs_inode_attrs *iattrs;
 136         void *old_secdata;
 137         size_t old_secdata_len;
 138
 139         if (!sd->s_iattr) {
 140                 sd->s_iattr = sysfs_init_inode_attrs(sd);
 141                 if (!sd->s_iattr)
 142                         return -ENOMEM;
 143         }
 144
 145         iattrs = sd->s_iattr;
 146         old_secdata = iattrs->ia_secdata;
 147         old_secdata_len = iattrs->ia_secdata_len;
 148
 149         iattrs->ia_secdata = *secdata;
 150         iattrs->ia_secdata_len = *secdata_len;
 151
 152         *secdata = old_secdata;
 153         *secdata_len = old_secdata_len;
 154         return 0;
 155 }
 156
 157 int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 158                 size_t size, int flags)
 159 {
 160         struct sysfs_dirent *sd = dentry->d_fsdata;
 161         void *secdata;
 162         int error;
 163         u32 secdata_len = 0;
 164
 165         if (!sd)
 166                 return -EINVAL;
 167
 168         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
 169                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 170                 error = security_inode_setsecurity(dentry->d_inode, suffix,
 171                                                 value, size, flags);
 172                 if (error)
 173                         goto out;
 174                 error = security_inode_getsecctx(dentry->d_inode,
 175                                                 &secdata, &secdata_len);
 176                 if (error)
 177                         goto out;
 178
 179                 mutex_lock(&sysfs_mutex);
 180                 error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
 181                 mutex_unlock(&sysfs_mutex);
 182
 183                 if (secdata)
 184                         security_release_secctx(secdata, secdata_len);
 185         } else
 186                 return -EINVAL;
 187 out:
 188         return error;
 189 }
 190
 191 static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
 192 {
 193         inode->i_mode = mode;
 194         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 195 }
 196
 197 static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
 198 {
 199         inode->i_uid = iattr->ia_uid;
 200         inode->i_gid = iattr->ia_gid;
 201         inode->i_atime = iattr->ia_atime;
 202         inode->i_mtime = iattr->ia_mtime;
 203         inode->i_ctime = iattr->ia_ctime;
 204 }
 205
 206 static int sysfs_count_nlink(struct sysfs_dirent *sd)
 207 {
 208         struct sysfs_dirent *child;
 209         int nr = 0;
 210
 211         for (child = sd->s_dir.children; child; child = child->s_sibling)
 212                 if (sysfs_type(child) == SYSFS_DIR)
 213                         nr++;
 214
 215         return nr + 2;
 216 }
 217
 218 static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
 219 {
 220         struct sysfs_inode_attrs *iattrs = sd->s_iattr;
 221
 222         inode->i_mode = sd->s_mode;
 223         if (iattrs) {
 224                 /* sysfs_dirent has non-default attributes
 225                  * get them from persistent copy in sysfs_dirent
 226                  */
 227                 set_inode_attr(inode, &iattrs->ia_iattr);
 228                 security_inode_notifysecctx(inode,
 229                                             iattrs->ia_secdata,
 230                                             iattrs->ia_secdata_len);
 231         }
 232
 233         if (sysfs_type(sd) == SYSFS_DIR)
 234                 inode->i_nlink = sysfs_count_nlink(sd);
 235 }
 236
 237 int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 238 {
 239         struct sysfs_dirent *sd = dentry->d_fsdata;
 240         struct inode *inode = dentry->d_inode;
 241
 242         mutex_lock(&sysfs_mutex);
 243         sysfs_refresh_inode(sd, inode);
 244         mutex_unlock(&sysfs_mutex);
 245
 246         generic_fillattr(inode, stat);
 247         return 0;
 248 }
 249
 250 static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
 251 {
 252         struct bin_attribute *bin_attr;
 253
 254         inode->i_private = sysfs_get(sd);
 255         inode->i_mapping->a_ops = &sysfs_aops;
 256         inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
 257         inode->i_op = &sysfs_inode_operations;
 258
 259         set_default_inode_attr(inode, sd->s_mode);
 260         sysfs_refresh_inode(sd, inode);
 261
 262         /* initialize inode according to type */
 263         switch (sysfs_type(sd)) {
 264         case SYSFS_DIR:
 265                 inode->i_op = &sysfs_dir_inode_operations;
 266                 inode->i_fop = &sysfs_dir_operations;
 267                 break;
 268         case SYSFS_KOBJ_ATTR:
 269                 inode->i_size = PAGE_SIZE;
 270                 inode->i_fop = &sysfs_file_operations;
 271                 break;
 272         case SYSFS_KOBJ_BIN_ATTR:
 273                 bin_attr = sd->s_bin_attr.bin_attr;
 274                 inode->i_size = bin_attr->size;
 275                 inode->i_fop = &bin_fops;
 276                 break;
 277         case SYSFS_KOBJ_LINK:
 278                 inode->i_op = &sysfs_symlink_inode_operations;
 279                 break;
 280         default:
 281                 BUG();
 282         }
 283
 284         unlock_new_inode(inode);
 285 }
 286
 287 /**
 288  *      sysfs_get_inode - get inode for sysfs_dirent
 289  *      @sb: super block
 290  *      @sd: sysfs_dirent to allocate inode for
 291  *
 292  *      Get inode for @sd.  If such inode doesn't exist, a new inode
 293  *      is allocated and basics are initialized.  New inode is
 294  *      returned locked.
 295  *
 296  *      LOCKING:
 297  *      Kernel thread context (may sleep).
 298  *
 299  *      RETURNS:
 300  *      Pointer to allocated inode on success, NULL on failure.
 301  */
 302 struct inode * sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd)
 303 {
 304         struct inode *inode;
 305
 306         inode = iget_locked(sb, sd->s_ino);
 307         if (inode && (inode->i_state & I_NEW))
 308                 sysfs_init_inode(sd, inode);
 309
 310         return inode;
 311 }
 312
 313 /*
 314  * The sysfs_dirent serves as both an inode and a directory entry for sysfs.
 315  * To prevent the sysfs inode numbers from being freed prematurely we take a
 316  * reference to sysfs_dirent from the sysfs inode.  A
 317  * super_operations.evict_inode() implementation is needed to drop that
 318  * reference upon inode destruction.
 319  */
 320 void sysfs_evict_inode(struct inode *inode)
 321 {
 322         struct sysfs_dirent *sd  = inode->i_private;
 323
 324         truncate_inode_pages(&inode->i_data, 0);
 325         end_writeback(inode);
 326         sysfs_put(sd);
 327 }
 328
 329 int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const void *ns, const char *name)
 330 {
 331         struct sysfs_addrm_cxt acxt;
 332         struct sysfs_dirent *sd;
 333
 334         if (!dir_sd)
 335                 return -ENOENT;
 336
 337         sysfs_addrm_start(&acxt, dir_sd);
 338
 339         sd = sysfs_find_dirent(dir_sd, ns, name);
 340         if (sd && (sd->s_ns != ns))
 341                 sd = NULL;
 342         if (sd)
 343                 sysfs_remove_one(&acxt, sd);
 344
 345         sysfs_addrm_finish(&acxt);
 346
 347         if (sd)
 348                 return 0;
 349         else
 350                 return -ENOENT;
 351 }
 352
 353 int sysfs_permission(struct inode *inode, int mask, unsigned int flags)
 354 {
 355         struct sysfs_dirent *sd;
 356
 357         if (flags & IPERM_FLAG_RCU)
 358                 return -ECHILD;
 359
 360         sd = inode->i_private;
 361
 362         mutex_lock(&sysfs_mutex);
 363         sysfs_refresh_inode(sd, inode);
 364         mutex_unlock(&sysfs_mutex);
 365
 366         return generic_permission(inode, mask, flags, NULL);
 367 }