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