diff options
Diffstat (limited to 'fs/ubifs/xattr.c')
| -rw-r--r-- | fs/ubifs/xattr.c | 679 |
1 files changed, 679 insertions, 0 deletions
diff --git a/fs/ubifs/xattr.c b/fs/ubifs/xattr.c new file mode 100644 index 000000000..f5ad1ede7 --- /dev/null +++ b/fs/ubifs/xattr.c @@ -0,0 +1,679 @@ +/* + * This file is part of UBIFS. + * + * Copyright (C) 2006-2008 Nokia Corporation. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * You should have received a copy of the GNU General Public License along with + * this program; if not, write to the Free Software Foundation, Inc., 51 + * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + * Authors: Artem Bityutskiy (Битюцкий Артём) + * Adrian Hunter + */ + +/* + * This file implements UBIFS extended attributes support. + * + * Extended attributes are implemented as regular inodes with attached data, + * which limits extended attribute size to UBIFS block size (4KiB). Names of + * extended attributes are described by extended attribute entries (xentries), + * which are almost identical to directory entries, but have different key type. + * + * In other words, the situation with extended attributes is very similar to + * directories. Indeed, any inode (but of course not xattr inodes) may have a + * number of associated xentries, just like directory inodes have associated + * directory entries. Extended attribute entries store the name of the extended + * attribute, the host inode number, and the extended attribute inode number. + * Similarly, direntries store the name, the parent and the target inode + * numbers. Thus, most of the common UBIFS mechanisms may be re-used for + * extended attributes. + * + * The number of extended attributes is not limited, but there is Linux + * limitation on the maximum possible size of the list of all extended + * attributes associated with an inode (%XATTR_LIST_MAX), so UBIFS makes sure + * the sum of all extended attribute names of the inode does not exceed that + * limit. + * + * Extended attributes are synchronous, which means they are written to the + * flash media synchronously and there is no write-back for extended attribute + * inodes. The extended attribute values are not stored in compressed form on + * the media. + * + * Since extended attributes are represented by regular inodes, they are cached + * in the VFS inode cache. The xentries are cached in the LNC cache (see + * tnc.c). + * + * ACL support is not implemented. + */ + +#include "ubifs.h" +#include <linux/fs.h> +#include <linux/slab.h> +#include <linux/xattr.h> + +/* + * Limit the number of extended attributes per inode so that the total size + * (@xattr_size) is guaranteeded to fit in an 'unsigned int'. + */ +#define MAX_XATTRS_PER_INODE 65535 + +/* + * Extended attribute type constants. + * + * USER_XATTR: user extended attribute ("user.*") + * TRUSTED_XATTR: trusted extended attribute ("trusted.*) + * SECURITY_XATTR: security extended attribute ("security.*") + */ +enum { + USER_XATTR, + TRUSTED_XATTR, + SECURITY_XATTR, +}; + +static const struct inode_operations empty_iops; +static const struct file_operations empty_fops; + +/** + * create_xattr - create an extended attribute. + * @c: UBIFS file-system description object + * @host: host inode + * @nm: extended attribute name + * @value: extended attribute value + * @size: size of extended attribute value + * + * This is a helper function which creates an extended attribute of name @nm + * and value @value for inode @host. The host inode is also updated on flash + * because the ctime and extended attribute accounting data changes. This + * function returns zero in case of success and a negative error code in case + * of failure. + */ +static int create_xattr(struct ubifs_info *c, struct inode *host, + const struct fscrypt_name *nm, const void *value, int size) +{ + int err, names_len; + struct inode *inode; + struct ubifs_inode *ui, *host_ui = ubifs_inode(host); + struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1, + .new_ino_d = ALIGN(size, 8), .dirtied_ino = 1, + .dirtied_ino_d = ALIGN(host_ui->data_len, 8) }; + + if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE) { + ubifs_err(c, "inode %lu already has too many xattrs (%d), cannot create more", + host->i_ino, host_ui->xattr_cnt); + return -ENOSPC; + } + /* + * Linux limits the maximum size of the extended attribute names list + * to %XATTR_LIST_MAX. This means we should not allow creating more + * extended attributes if the name list becomes larger. This limitation + * is artificial for UBIFS, though. + */ + names_len = host_ui->xattr_names + host_ui->xattr_cnt + fname_len(nm) + 1; + if (names_len > XATTR_LIST_MAX) { + ubifs_err(c, "cannot add one more xattr name to inode %lu, total names length would become %d, max. is %d", + host->i_ino, names_len, XATTR_LIST_MAX); + return -ENOSPC; + } + + err = ubifs_budget_space(c, &req); + if (err) + return err; + + inode = ubifs_new_inode(c, host, S_IFREG | S_IRWXUGO); + if (IS_ERR(inode)) { + err = PTR_ERR(inode); + goto out_budg; + } + + /* Re-define all operations to be "nothing" */ + inode->i_mapping->a_ops = &empty_aops; + inode->i_op = &empty_iops; + inode->i_fop = &empty_fops; + + inode->i_flags |= S_SYNC | S_NOATIME | S_NOCMTIME; + ui = ubifs_inode(inode); + ui->xattr = 1; + ui->flags |= UBIFS_XATTR_FL; + ui->data = kmemdup(value, size, GFP_NOFS); + if (!ui->data) { + err = -ENOMEM; + goto out_free; + } + inode->i_size = ui->ui_size = size; + ui->data_len = size; + + mutex_lock(&host_ui->ui_mutex); + host->i_ctime = current_time(host); + host_ui->xattr_cnt += 1; + host_ui->xattr_size += CALC_DENT_SIZE(fname_len(nm)); + host_ui->xattr_size += CALC_XATTR_BYTES(size); + host_ui->xattr_names += fname_len(nm); + + /* + * We handle UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT here because we + * have to set the UBIFS_CRYPT_FL flag on the host inode. + * To avoid multiple updates of the same inode in the same operation, + * let's do it here. + */ + if (strcmp(fname_name(nm), UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT) == 0) + host_ui->flags |= UBIFS_CRYPT_FL; + + err = ubifs_jnl_update(c, host, nm, inode, 0, 1); + if (err) + goto out_cancel; + ubifs_set_inode_flags(host); + mutex_unlock(&host_ui->ui_mutex); + + ubifs_release_budget(c, &req); + insert_inode_hash(inode); + iput(inode); + return 0; + +out_cancel: + host_ui->xattr_cnt -= 1; + host_ui->xattr_size -= CALC_DENT_SIZE(fname_len(nm)); + host_ui->xattr_size -= CALC_XATTR_BYTES(size); + host_ui->xattr_names -= fname_len(nm); + host_ui->flags &= ~UBIFS_CRYPT_FL; + mutex_unlock(&host_ui->ui_mutex); +out_free: + make_bad_inode(inode); + iput(inode); +out_budg: + ubifs_release_budget(c, &req); + return err; +} + +/** + * change_xattr - change an extended attribute. + * @c: UBIFS file-system description object + * @host: host inode + * @inode: extended attribute inode + * @value: extended attribute value + * @size: size of extended attribute value + * + * This helper function changes the value of extended attribute @inode with new + * data from @value. Returns zero in case of success and a negative error code + * in case of failure. + */ +static int change_xattr(struct ubifs_info *c, struct inode *host, + struct inode *inode, const void *value, int size) +{ + int err; + struct ubifs_inode *host_ui = ubifs_inode(host); + struct ubifs_inode *ui = ubifs_inode(inode); + void *buf = NULL; + int old_size; + struct ubifs_budget_req req = { .dirtied_ino = 2, + .dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) }; + + ubifs_assert(c, ui->data_len == inode->i_size); + err = ubifs_budget_space(c, &req); + if (err) + return err; + + buf = kmemdup(value, size, GFP_NOFS); + if (!buf) { + err = -ENOMEM; + goto out_free; + } + mutex_lock(&ui->ui_mutex); + kfree(ui->data); + ui->data = buf; + inode->i_size = ui->ui_size = size; + old_size = ui->data_len; + ui->data_len = size; + mutex_unlock(&ui->ui_mutex); + + mutex_lock(&host_ui->ui_mutex); + host->i_ctime = current_time(host); + host_ui->xattr_size -= CALC_XATTR_BYTES(old_size); + host_ui->xattr_size += CALC_XATTR_BYTES(size); + + /* + * It is important to write the host inode after the xattr inode + * because if the host inode gets synchronized (via 'fsync()'), then + * the extended attribute inode gets synchronized, because it goes + * before the host inode in the write-buffer. + */ + err = ubifs_jnl_change_xattr(c, inode, host); + if (err) + goto out_cancel; + mutex_unlock(&host_ui->ui_mutex); + + ubifs_release_budget(c, &req); + return 0; + +out_cancel: + host_ui->xattr_size -= CALC_XATTR_BYTES(size); + host_ui->xattr_size += CALC_XATTR_BYTES(old_size); + mutex_unlock(&host_ui->ui_mutex); + make_bad_inode(inode); +out_free: + ubifs_release_budget(c, &req); + return err; +} + +static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum) +{ + struct inode *inode; + + inode = ubifs_iget(c->vfs_sb, inum); + if (IS_ERR(inode)) { + ubifs_err(c, "dead extended attribute entry, error %d", + (int)PTR_ERR(inode)); + return inode; + } + if (ubifs_inode(inode)->xattr) + return inode; + ubifs_err(c, "corrupt extended attribute entry"); + iput(inode); + return ERR_PTR(-EINVAL); +} + +int ubifs_xattr_set(struct inode *host, const char *name, const void *value, + size_t size, int flags, bool check_lock) +{ + struct inode *inode; + struct ubifs_info *c = host->i_sb->s_fs_info; + struct fscrypt_name nm = { .disk_name = FSTR_INIT((char *)name, strlen(name))}; + struct ubifs_dent_node *xent; + union ubifs_key key; + int err; + + if (check_lock) + ubifs_assert(c, inode_is_locked(host)); + + if (size > UBIFS_MAX_INO_DATA) + return -ERANGE; + + if (fname_len(&nm) > UBIFS_MAX_NLEN) + return -ENAMETOOLONG; + + xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); + if (!xent) + return -ENOMEM; + + /* + * The extended attribute entries are stored in LNC, so multiple + * look-ups do not involve reading the flash. + */ + xent_key_init(c, &key, host->i_ino, &nm); + err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); + if (err) { + if (err != -ENOENT) + goto out_free; + + if (flags & XATTR_REPLACE) + /* We are asked not to create the xattr */ + err = -ENODATA; + else + err = create_xattr(c, host, &nm, value, size); + goto out_free; + } + + if (flags & XATTR_CREATE) { + /* We are asked not to replace the xattr */ + err = -EEXIST; + goto out_free; + } + + inode = iget_xattr(c, le64_to_cpu(xent->inum)); + if (IS_ERR(inode)) { + err = PTR_ERR(inode); + goto out_free; + } + + err = change_xattr(c, host, inode, value, size); + iput(inode); + +out_free: + kfree(xent); + return err; +} + +ssize_t ubifs_xattr_get(struct inode *host, const char *name, void *buf, + size_t size) +{ + struct inode *inode; + struct ubifs_info *c = host->i_sb->s_fs_info; + struct fscrypt_name nm = { .disk_name = FSTR_INIT((char *)name, strlen(name))}; + struct ubifs_inode *ui; + struct ubifs_dent_node *xent; + union ubifs_key key; + int err; + + if (fname_len(&nm) > UBIFS_MAX_NLEN) + return -ENAMETOOLONG; + + xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); + if (!xent) + return -ENOMEM; + + xent_key_init(c, &key, host->i_ino, &nm); + err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); + if (err) { + if (err == -ENOENT) + err = -ENODATA; + goto out_unlock; + } + + inode = iget_xattr(c, le64_to_cpu(xent->inum)); + if (IS_ERR(inode)) { + err = PTR_ERR(inode); + goto out_unlock; + } + + ui = ubifs_inode(inode); + ubifs_assert(c, inode->i_size == ui->data_len); + ubifs_assert(c, ubifs_inode(host)->xattr_size > ui->data_len); + + mutex_lock(&ui->ui_mutex); + if (buf) { + /* If @buf is %NULL we are supposed to return the length */ + if (ui->data_len > size) { + err = -ERANGE; + goto out_iput; + } + + memcpy(buf, ui->data, ui->data_len); + } + err = ui->data_len; + +out_iput: + mutex_unlock(&ui->ui_mutex); + iput(inode); +out_unlock: + kfree(xent); + return err; +} + +static bool xattr_visible(const char *name) +{ + /* File encryption related xattrs are for internal use only */ + if (strcmp(name, UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT) == 0) + return false; + + /* Show trusted namespace only for "power" users */ + if (strncmp(name, XATTR_TRUSTED_PREFIX, + XATTR_TRUSTED_PREFIX_LEN) == 0 && !capable(CAP_SYS_ADMIN)) + return false; + + return true; +} + +ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size) +{ + union ubifs_key key; + struct inode *host = d_inode(dentry); + struct ubifs_info *c = host->i_sb->s_fs_info; + struct ubifs_inode *host_ui = ubifs_inode(host); + struct ubifs_dent_node *xent, *pxent = NULL; + int err, len, written = 0; + struct fscrypt_name nm = {0}; + + dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino, + dentry, size); + + len = host_ui->xattr_names + host_ui->xattr_cnt; + if (!buffer) + /* + * We should return the minimum buffer size which will fit a + * null-terminated list of all the extended attribute names. + */ + return len; + + if (len > size) + return -ERANGE; + + lowest_xent_key(c, &key, host->i_ino); + while (1) { + xent = ubifs_tnc_next_ent(c, &key, &nm); + if (IS_ERR(xent)) { + err = PTR_ERR(xent); + break; + } + + fname_name(&nm) = xent->name; + fname_len(&nm) = le16_to_cpu(xent->nlen); + + if (xattr_visible(xent->name)) { + memcpy(buffer + written, fname_name(&nm), fname_len(&nm) + 1); + written += fname_len(&nm) + 1; + } + + kfree(pxent); + pxent = xent; + key_read(c, &xent->key, &key); + } + + kfree(pxent); + if (err != -ENOENT) { + ubifs_err(c, "cannot find next direntry, error %d", err); + return err; + } + + ubifs_assert(c, written <= size); + return written; +} + +static int remove_xattr(struct ubifs_info *c, struct inode *host, + struct inode *inode, const struct fscrypt_name *nm) +{ + int err; + struct ubifs_inode *host_ui = ubifs_inode(host); + struct ubifs_inode *ui = ubifs_inode(inode); + struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1, + .dirtied_ino_d = ALIGN(host_ui->data_len, 8) }; + + ubifs_assert(c, ui->data_len == inode->i_size); + + err = ubifs_budget_space(c, &req); + if (err) + return err; + + mutex_lock(&host_ui->ui_mutex); + host->i_ctime = current_time(host); + host_ui->xattr_cnt -= 1; + host_ui->xattr_size -= CALC_DENT_SIZE(fname_len(nm)); + host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len); + host_ui->xattr_names -= fname_len(nm); + + err = ubifs_jnl_delete_xattr(c, host, inode, nm); + if (err) + goto out_cancel; + mutex_unlock(&host_ui->ui_mutex); + + ubifs_release_budget(c, &req); + return 0; + +out_cancel: + host_ui->xattr_cnt += 1; + host_ui->xattr_size += CALC_DENT_SIZE(fname_len(nm)); + host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len); + host_ui->xattr_names += fname_len(nm); + mutex_unlock(&host_ui->ui_mutex); + ubifs_release_budget(c, &req); + make_bad_inode(inode); + return err; +} + +/** + * ubifs_evict_xattr_inode - Evict an xattr inode. + * @c: UBIFS file-system description object + * @xattr_inum: xattr inode number + * + * When an inode that hosts xattrs is being removed we have to make sure + * that cached inodes of the xattrs also get removed from the inode cache + * otherwise we'd waste memory. This function looks up an inode from the + * inode cache and clears the link counter such that iput() will evict + * the inode. + */ +void ubifs_evict_xattr_inode(struct ubifs_info *c, ino_t xattr_inum) +{ + struct inode *inode; + + inode = ilookup(c->vfs_sb, xattr_inum); + if (inode) { + clear_nlink(inode); + iput(inode); + } +} + +static int ubifs_xattr_remove(struct inode *host, const char *name) +{ + struct inode *inode; + struct ubifs_info *c = host->i_sb->s_fs_info; + struct fscrypt_name nm = { .disk_name = FSTR_INIT((char *)name, strlen(name))}; + struct ubifs_dent_node *xent; + union ubifs_key key; + int err; + + ubifs_assert(c, inode_is_locked(host)); + + if (fname_len(&nm) > UBIFS_MAX_NLEN) + return -ENAMETOOLONG; + + xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); + if (!xent) + return -ENOMEM; + + xent_key_init(c, &key, host->i_ino, &nm); + err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); + if (err) { + if (err == -ENOENT) + err = -ENODATA; + goto out_free; + } + + inode = iget_xattr(c, le64_to_cpu(xent->inum)); + if (IS_ERR(inode)) { + err = PTR_ERR(inode); + goto out_free; + } + + ubifs_assert(c, inode->i_nlink == 1); + clear_nlink(inode); + err = remove_xattr(c, host, inode, &nm); + if (err) + set_nlink(inode, 1); + + /* If @i_nlink is 0, 'iput()' will delete the inode */ + iput(inode); + +out_free: + kfree(xent); + return err; +} + +#ifdef CONFIG_UBIFS_FS_SECURITY +static int init_xattrs(struct inode *inode, const struct xattr *xattr_array, + void *fs_info) +{ + const struct xattr *xattr; + char *name; + int err = 0; + + for (xattr = xattr_array; xattr->name != NULL; xattr++) { + name = kmalloc(XATTR_SECURITY_PREFIX_LEN + + strlen(xattr->name) + 1, GFP_NOFS); + if (!name) { + err = -ENOMEM; + break; + } + strcpy(name, XATTR_SECURITY_PREFIX); + strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name); + /* + * creating a new inode without holding the inode rwsem, + * no need to check whether inode is locked. + */ + err = ubifs_xattr_set(inode, name, xattr->value, + xattr->value_len, 0, false); + kfree(name); + if (err < 0) + break; + } + + return err; +} + +int ubifs_init_security(struct inode *dentry, struct inode *inode, + const struct qstr *qstr) +{ + int err; + + err = security_inode_init_security(inode, dentry, qstr, + &init_xattrs, 0); + if (err) { + struct ubifs_info *c = dentry->i_sb->s_fs_info; + ubifs_err(c, "cannot initialize security for inode %lu, error %d", + inode->i_ino, err); + } + return err; +} +#endif + +static int xattr_get(const struct xattr_handler *handler, + struct dentry *dentry, struct inode *inode, + const char *name, void *buffer, size_t size) +{ + dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name, + inode->i_ino, dentry, size); + + name = xattr_full_name(handler, name); + return ubifs_xattr_get(inode, name, buffer, size); +} + +static int xattr_set(const struct xattr_handler *handler, + struct dentry *dentry, struct inode *inode, + const char *name, const void *value, + size_t size, int flags) +{ + dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd", + name, inode->i_ino, dentry, size); + + name = xattr_full_name(handler, name); + + if (value) + return ubifs_xattr_set(inode, name, value, size, flags, true); + else + return ubifs_xattr_remove(inode, name); +} + +static const struct xattr_handler ubifs_user_xattr_handler = { + .prefix = XATTR_USER_PREFIX, + .get = xattr_get, + .set = xattr_set, +}; + +static const struct xattr_handler ubifs_trusted_xattr_handler = { + .prefix = XATTR_TRUSTED_PREFIX, + .get = xattr_get, + .set = xattr_set, +}; + +#ifdef CONFIG_UBIFS_FS_SECURITY +static const struct xattr_handler ubifs_security_xattr_handler = { + .prefix = XATTR_SECURITY_PREFIX, + .get = xattr_get, + .set = xattr_set, +}; +#endif + +const struct xattr_handler *ubifs_xattr_handlers[] = { + &ubifs_user_xattr_handler, + &ubifs_trusted_xattr_handler, +#ifdef CONFIG_UBIFS_FS_SECURITY + &ubifs_security_xattr_handler, +#endif + NULL +}; |