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