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![Christian Brauner](/assets/img/avatar_default.png)
The posix acl permission checking helpers determine whether a caller is privileged over an inode according to the acls associated with the inode. Add helpers that make it possible to handle acls on idmapped mounts. The vfs and the filesystems targeted by this first iteration make use of posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to translate basic posix access and default permissions such as the ACL_USER and ACL_GROUP type according to the initial user namespace (or the superblock's user namespace) to and from the caller's current user namespace. Adapt these two helpers to handle idmapped mounts whereby we either map from or into the mount's user namespace depending on in which direction we're translating. Similarly, cap_convert_nscap() is used by the vfs to translate user namespace and non-user namespace aware filesystem capabilities from the superblock's user namespace to the caller's user namespace. Enable it to handle idmapped mounts by accounting for the mount's user namespace. In addition the fileystems targeted in the first iteration of this patch series make use of the posix_acl_chmod() and, posix_acl_update_mode() helpers. Both helpers perform permission checks on the target inode. Let them handle idmapped mounts. These two helpers are called when posix acls are set by the respective filesystems to handle this case we extend the ->set() method to take an additional user namespace argument to pass the mount's user namespace down. Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com Cc: Christoph Hellwig <hch@lst.de> Cc: David Howells <dhowells@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
481 lines
12 KiB
C
481 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2007 Red Hat. All rights reserved.
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*/
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/rwsem.h>
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#include <linux/xattr.h>
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#include <linux/security.h>
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#include <linux/posix_acl_xattr.h>
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#include <linux/iversion.h>
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#include <linux/sched/mm.h>
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#include "ctree.h"
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#include "btrfs_inode.h"
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#include "transaction.h"
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#include "xattr.h"
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#include "disk-io.h"
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#include "props.h"
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#include "locking.h"
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int btrfs_getxattr(struct inode *inode, const char *name,
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void *buffer, size_t size)
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{
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struct btrfs_dir_item *di;
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struct btrfs_root *root = BTRFS_I(inode)->root;
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struct btrfs_path *path;
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struct extent_buffer *leaf;
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int ret = 0;
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unsigned long data_ptr;
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path = btrfs_alloc_path();
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if (!path)
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return -ENOMEM;
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/* lookup the xattr by name */
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di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
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name, strlen(name), 0);
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if (!di) {
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ret = -ENODATA;
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goto out;
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} else if (IS_ERR(di)) {
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ret = PTR_ERR(di);
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goto out;
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}
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leaf = path->nodes[0];
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/* if size is 0, that means we want the size of the attr */
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if (!size) {
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ret = btrfs_dir_data_len(leaf, di);
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goto out;
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}
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/* now get the data out of our dir_item */
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if (btrfs_dir_data_len(leaf, di) > size) {
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ret = -ERANGE;
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goto out;
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}
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/*
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* The way things are packed into the leaf is like this
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* |struct btrfs_dir_item|name|data|
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* where name is the xattr name, so security.foo, and data is the
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* content of the xattr. data_ptr points to the location in memory
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* where the data starts in the in memory leaf
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*/
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data_ptr = (unsigned long)((char *)(di + 1) +
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btrfs_dir_name_len(leaf, di));
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read_extent_buffer(leaf, buffer, data_ptr,
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btrfs_dir_data_len(leaf, di));
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ret = btrfs_dir_data_len(leaf, di);
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out:
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btrfs_free_path(path);
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return ret;
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}
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int btrfs_setxattr(struct btrfs_trans_handle *trans, struct inode *inode,
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const char *name, const void *value, size_t size, int flags)
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{
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struct btrfs_dir_item *di = NULL;
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struct btrfs_root *root = BTRFS_I(inode)->root;
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struct btrfs_fs_info *fs_info = root->fs_info;
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struct btrfs_path *path;
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size_t name_len = strlen(name);
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int ret = 0;
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ASSERT(trans);
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if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
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return -ENOSPC;
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path = btrfs_alloc_path();
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if (!path)
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return -ENOMEM;
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path->skip_release_on_error = 1;
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if (!value) {
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di = btrfs_lookup_xattr(trans, root, path,
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btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
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if (!di && (flags & XATTR_REPLACE))
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ret = -ENODATA;
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else if (IS_ERR(di))
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ret = PTR_ERR(di);
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else if (di)
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ret = btrfs_delete_one_dir_name(trans, root, path, di);
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goto out;
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}
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/*
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* For a replace we can't just do the insert blindly.
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* Do a lookup first (read-only btrfs_search_slot), and return if xattr
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* doesn't exist. If it exists, fall down below to the insert/replace
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* path - we can't race with a concurrent xattr delete, because the VFS
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* locks the inode's i_mutex before calling setxattr or removexattr.
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*/
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if (flags & XATTR_REPLACE) {
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ASSERT(inode_is_locked(inode));
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di = btrfs_lookup_xattr(NULL, root, path,
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btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
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if (!di)
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ret = -ENODATA;
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else if (IS_ERR(di))
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ret = PTR_ERR(di);
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if (ret)
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goto out;
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btrfs_release_path(path);
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di = NULL;
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}
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ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
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name, name_len, value, size);
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if (ret == -EOVERFLOW) {
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/*
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* We have an existing item in a leaf, split_leaf couldn't
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* expand it. That item might have or not a dir_item that
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* matches our target xattr, so lets check.
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*/
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ret = 0;
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btrfs_assert_tree_locked(path->nodes[0]);
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di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
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if (!di && !(flags & XATTR_REPLACE)) {
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ret = -ENOSPC;
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goto out;
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}
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} else if (ret == -EEXIST) {
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ret = 0;
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di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
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ASSERT(di); /* logic error */
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} else if (ret) {
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goto out;
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}
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if (di && (flags & XATTR_CREATE)) {
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ret = -EEXIST;
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goto out;
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}
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if (di) {
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/*
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* We're doing a replace, and it must be atomic, that is, at
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* any point in time we have either the old or the new xattr
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* value in the tree. We don't want readers (getxattr and
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* listxattrs) to miss a value, this is specially important
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* for ACLs.
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*/
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const int slot = path->slots[0];
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struct extent_buffer *leaf = path->nodes[0];
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const u16 old_data_len = btrfs_dir_data_len(leaf, di);
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const u32 item_size = btrfs_item_size_nr(leaf, slot);
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const u32 data_size = sizeof(*di) + name_len + size;
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struct btrfs_item *item;
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unsigned long data_ptr;
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char *ptr;
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if (size > old_data_len) {
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if (btrfs_leaf_free_space(leaf) <
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(size - old_data_len)) {
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ret = -ENOSPC;
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goto out;
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}
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}
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if (old_data_len + name_len + sizeof(*di) == item_size) {
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/* No other xattrs packed in the same leaf item. */
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if (size > old_data_len)
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btrfs_extend_item(path, size - old_data_len);
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else if (size < old_data_len)
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btrfs_truncate_item(path, data_size, 1);
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} else {
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/* There are other xattrs packed in the same item. */
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ret = btrfs_delete_one_dir_name(trans, root, path, di);
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if (ret)
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goto out;
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btrfs_extend_item(path, data_size);
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}
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item = btrfs_item_nr(slot);
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ptr = btrfs_item_ptr(leaf, slot, char);
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ptr += btrfs_item_size(leaf, item) - data_size;
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di = (struct btrfs_dir_item *)ptr;
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btrfs_set_dir_data_len(leaf, di, size);
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data_ptr = ((unsigned long)(di + 1)) + name_len;
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write_extent_buffer(leaf, value, data_ptr, size);
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btrfs_mark_buffer_dirty(leaf);
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} else {
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/*
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* Insert, and we had space for the xattr, so path->slots[0] is
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* where our xattr dir_item is and btrfs_insert_xattr_item()
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* filled it.
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*/
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}
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out:
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btrfs_free_path(path);
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if (!ret) {
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set_bit(BTRFS_INODE_COPY_EVERYTHING,
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&BTRFS_I(inode)->runtime_flags);
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clear_bit(BTRFS_INODE_NO_XATTRS, &BTRFS_I(inode)->runtime_flags);
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}
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return ret;
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}
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/*
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* @value: "" makes the attribute to empty, NULL removes it
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*/
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int btrfs_setxattr_trans(struct inode *inode, const char *name,
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const void *value, size_t size, int flags)
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{
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struct btrfs_root *root = BTRFS_I(inode)->root;
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struct btrfs_trans_handle *trans;
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int ret;
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trans = btrfs_start_transaction(root, 2);
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if (IS_ERR(trans))
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return PTR_ERR(trans);
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ret = btrfs_setxattr(trans, inode, name, value, size, flags);
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if (ret)
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goto out;
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inode_inc_iversion(inode);
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inode->i_ctime = current_time(inode);
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ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
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BUG_ON(ret);
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out:
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btrfs_end_transaction(trans);
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return ret;
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}
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ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
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{
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struct btrfs_key key;
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struct inode *inode = d_inode(dentry);
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struct btrfs_root *root = BTRFS_I(inode)->root;
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struct btrfs_path *path;
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int ret = 0;
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size_t total_size = 0, size_left = size;
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/*
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* ok we want all objects associated with this id.
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* NOTE: we set key.offset = 0; because we want to start with the
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* first xattr that we find and walk forward
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*/
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key.objectid = btrfs_ino(BTRFS_I(inode));
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key.type = BTRFS_XATTR_ITEM_KEY;
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key.offset = 0;
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path = btrfs_alloc_path();
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if (!path)
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return -ENOMEM;
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path->reada = READA_FORWARD;
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/* search for our xattrs */
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ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
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if (ret < 0)
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goto err;
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while (1) {
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struct extent_buffer *leaf;
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int slot;
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struct btrfs_dir_item *di;
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struct btrfs_key found_key;
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u32 item_size;
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u32 cur;
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leaf = path->nodes[0];
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slot = path->slots[0];
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/* this is where we start walking through the path */
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if (slot >= btrfs_header_nritems(leaf)) {
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/*
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* if we've reached the last slot in this leaf we need
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* to go to the next leaf and reset everything
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*/
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ret = btrfs_next_leaf(root, path);
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if (ret < 0)
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goto err;
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else if (ret > 0)
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break;
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continue;
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}
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btrfs_item_key_to_cpu(leaf, &found_key, slot);
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/* check to make sure this item is what we want */
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if (found_key.objectid != key.objectid)
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break;
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if (found_key.type > BTRFS_XATTR_ITEM_KEY)
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break;
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if (found_key.type < BTRFS_XATTR_ITEM_KEY)
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goto next_item;
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di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
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item_size = btrfs_item_size_nr(leaf, slot);
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cur = 0;
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while (cur < item_size) {
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u16 name_len = btrfs_dir_name_len(leaf, di);
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u16 data_len = btrfs_dir_data_len(leaf, di);
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u32 this_len = sizeof(*di) + name_len + data_len;
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unsigned long name_ptr = (unsigned long)(di + 1);
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total_size += name_len + 1;
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/*
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* We are just looking for how big our buffer needs to
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* be.
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*/
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if (!size)
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goto next;
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if (!buffer || (name_len + 1) > size_left) {
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ret = -ERANGE;
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goto err;
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}
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read_extent_buffer(leaf, buffer, name_ptr, name_len);
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buffer[name_len] = '\0';
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size_left -= name_len + 1;
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buffer += name_len + 1;
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next:
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cur += this_len;
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di = (struct btrfs_dir_item *)((char *)di + this_len);
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}
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next_item:
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path->slots[0]++;
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}
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ret = total_size;
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err:
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btrfs_free_path(path);
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return ret;
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}
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static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
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struct dentry *unused, struct inode *inode,
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const char *name, void *buffer, size_t size)
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{
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name = xattr_full_name(handler, name);
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return btrfs_getxattr(inode, name, buffer, size);
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}
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static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
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struct user_namespace *mnt_userns,
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struct dentry *unused, struct inode *inode,
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const char *name, const void *buffer,
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size_t size, int flags)
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{
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name = xattr_full_name(handler, name);
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return btrfs_setxattr_trans(inode, name, buffer, size, flags);
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}
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static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
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struct user_namespace *mnt_userns,
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struct dentry *unused, struct inode *inode,
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const char *name, const void *value,
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size_t size, int flags)
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{
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int ret;
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struct btrfs_trans_handle *trans;
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struct btrfs_root *root = BTRFS_I(inode)->root;
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name = xattr_full_name(handler, name);
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ret = btrfs_validate_prop(name, value, size);
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if (ret)
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return ret;
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trans = btrfs_start_transaction(root, 2);
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if (IS_ERR(trans))
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return PTR_ERR(trans);
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ret = btrfs_set_prop(trans, inode, name, value, size, flags);
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if (!ret) {
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inode_inc_iversion(inode);
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inode->i_ctime = current_time(inode);
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ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
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BUG_ON(ret);
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}
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btrfs_end_transaction(trans);
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return ret;
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}
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static const struct xattr_handler btrfs_security_xattr_handler = {
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.prefix = XATTR_SECURITY_PREFIX,
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.get = btrfs_xattr_handler_get,
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.set = btrfs_xattr_handler_set,
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};
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static const struct xattr_handler btrfs_trusted_xattr_handler = {
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.prefix = XATTR_TRUSTED_PREFIX,
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.get = btrfs_xattr_handler_get,
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.set = btrfs_xattr_handler_set,
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};
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static const struct xattr_handler btrfs_user_xattr_handler = {
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.prefix = XATTR_USER_PREFIX,
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.get = btrfs_xattr_handler_get,
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.set = btrfs_xattr_handler_set,
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};
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static const struct xattr_handler btrfs_btrfs_xattr_handler = {
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.prefix = XATTR_BTRFS_PREFIX,
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.get = btrfs_xattr_handler_get,
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.set = btrfs_xattr_handler_set_prop,
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};
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const struct xattr_handler *btrfs_xattr_handlers[] = {
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&btrfs_security_xattr_handler,
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#ifdef CONFIG_BTRFS_FS_POSIX_ACL
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&posix_acl_access_xattr_handler,
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&posix_acl_default_xattr_handler,
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#endif
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&btrfs_trusted_xattr_handler,
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&btrfs_user_xattr_handler,
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&btrfs_btrfs_xattr_handler,
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NULL,
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};
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static int btrfs_initxattrs(struct inode *inode,
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const struct xattr *xattr_array, void *fs_private)
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{
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struct btrfs_trans_handle *trans = fs_private;
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const struct xattr *xattr;
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unsigned int nofs_flag;
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char *name;
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int err = 0;
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/*
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* We're holding a transaction handle, so use a NOFS memory allocation
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* context to avoid deadlock if reclaim happens.
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*/
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nofs_flag = memalloc_nofs_save();
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for (xattr = xattr_array; xattr->name != NULL; xattr++) {
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name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
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strlen(xattr->name) + 1, GFP_KERNEL);
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if (!name) {
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err = -ENOMEM;
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break;
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}
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strcpy(name, XATTR_SECURITY_PREFIX);
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strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
|
|
err = btrfs_setxattr(trans, inode, name, xattr->value,
|
|
xattr->value_len, 0);
|
|
kfree(name);
|
|
if (err < 0)
|
|
break;
|
|
}
|
|
memalloc_nofs_restore(nofs_flag);
|
|
return err;
|
|
}
|
|
|
|
int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
|
|
struct inode *inode, struct inode *dir,
|
|
const struct qstr *qstr)
|
|
{
|
|
return security_inode_init_security(inode, dir, qstr,
|
|
&btrfs_initxattrs, trans);
|
|
}
|