Linux 5.8-rc4

[linux/fpc-iii.git] / fs / btrfs / xattr.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Red Hat.  All rights reserved.
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/rwsem.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include <linux/posix_acl_xattr.h>
#include <linux/iversion.h>
#include <linux/sched/mm.h>
#include "ctree.h"
#include "btrfs_inode.h"
#include "transaction.h"
#include "xattr.h"
#include "disk-io.h"
#include "props.h"
#include "locking.h"

int btrfs_getxattr(struct inode *inode, const char *name,
                                void *buffer, size_t size)
{
        struct btrfs_dir_item *di;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret = 0;
        unsigned long data_ptr;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        /* lookup the xattr by name */
        di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
                        name, strlen(name), 0);
        if (!di) {
                ret = -ENODATA;
                goto out;
        } else if (IS_ERR(di)) {
                ret = PTR_ERR(di);
                goto out;
        }

        leaf = path->nodes[0];
        /* if size is 0, that means we want the size of the attr */
        if (!size) {
                ret = btrfs_dir_data_len(leaf, di);
                goto out;
        }

        /* now get the data out of our dir_item */
        if (btrfs_dir_data_len(leaf, di) > size) {
                ret = -ERANGE;
                goto out;
        }

        /*
         * The way things are packed into the leaf is like this
         * |struct btrfs_dir_item|name|data|
         * where name is the xattr name, so security.foo, and data is the
         * content of the xattr.  data_ptr points to the location in memory
         * where the data starts in the in memory leaf
         */
        data_ptr = (unsigned long)((char *)(di + 1) +
                                   btrfs_dir_name_len(leaf, di));
        read_extent_buffer(leaf, buffer, data_ptr,
                           btrfs_dir_data_len(leaf, di));
        ret = btrfs_dir_data_len(leaf, di);

out:
        btrfs_free_path(path);
        return ret;
}

int btrfs_setxattr(struct btrfs_trans_handle *trans, struct inode *inode,
                   const char *name, const void *value, size_t size, int flags)
{
        struct btrfs_dir_item *di = NULL;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_path *path;
        size_t name_len = strlen(name);
        int ret = 0;

        ASSERT(trans);

        if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
                return -ENOSPC;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
        path->skip_release_on_error = 1;

        if (!value) {
                di = btrfs_lookup_xattr(trans, root, path,
                                btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
                if (!di && (flags & XATTR_REPLACE))
                        ret = -ENODATA;
                else if (IS_ERR(di))
                        ret = PTR_ERR(di);
                else if (di)
                        ret = btrfs_delete_one_dir_name(trans, root, path, di);
                goto out;
        }

        /*
         * For a replace we can't just do the insert blindly.
         * Do a lookup first (read-only btrfs_search_slot), and return if xattr
         * doesn't exist. If it exists, fall down below to the insert/replace
         * path - we can't race with a concurrent xattr delete, because the VFS
         * locks the inode's i_mutex before calling setxattr or removexattr.
         */
        if (flags & XATTR_REPLACE) {
                ASSERT(inode_is_locked(inode));
                di = btrfs_lookup_xattr(NULL, root, path,
                                btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
                if (!di)
                        ret = -ENODATA;
                else if (IS_ERR(di))
                        ret = PTR_ERR(di);
                if (ret)
                        goto out;
                btrfs_release_path(path);
                di = NULL;
        }

        ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
                                      name, name_len, value, size);
        if (ret == -EOVERFLOW) {
                /*
                 * We have an existing item in a leaf, split_leaf couldn't
                 * expand it. That item might have or not a dir_item that
                 * matches our target xattr, so lets check.
                 */
                ret = 0;
                btrfs_assert_tree_locked(path->nodes[0]);
                di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
                if (!di && !(flags & XATTR_REPLACE)) {
                        ret = -ENOSPC;
                        goto out;
                }
        } else if (ret == -EEXIST) {
                ret = 0;
                di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
                ASSERT(di); /* logic error */
        } else if (ret) {
                goto out;
        }

        if (di && (flags & XATTR_CREATE)) {
                ret = -EEXIST;
                goto out;
        }

        if (di) {
                /*
                 * We're doing a replace, and it must be atomic, that is, at
                 * any point in time we have either the old or the new xattr
                 * value in the tree. We don't want readers (getxattr and
                 * listxattrs) to miss a value, this is specially important
                 * for ACLs.
                 */
                const int slot = path->slots[0];
                struct extent_buffer *leaf = path->nodes[0];
                const u16 old_data_len = btrfs_dir_data_len(leaf, di);
                const u32 item_size = btrfs_item_size_nr(leaf, slot);
                const u32 data_size = sizeof(*di) + name_len + size;
                struct btrfs_item *item;
                unsigned long data_ptr;
                char *ptr;

                if (size > old_data_len) {
                        if (btrfs_leaf_free_space(leaf) <
                            (size - old_data_len)) {
                                ret = -ENOSPC;
                                goto out;
                        }
                }

                if (old_data_len + name_len + sizeof(*di) == item_size) {
                        /* No other xattrs packed in the same leaf item. */
                        if (size > old_data_len)
                                btrfs_extend_item(path, size - old_data_len);
                        else if (size < old_data_len)
                                btrfs_truncate_item(path, data_size, 1);
                } else {
                        /* There are other xattrs packed in the same item. */
                        ret = btrfs_delete_one_dir_name(trans, root, path, di);
                        if (ret)
                                goto out;
                        btrfs_extend_item(path, data_size);
                }

                item = btrfs_item_nr(slot);
                ptr = btrfs_item_ptr(leaf, slot, char);
                ptr += btrfs_item_size(leaf, item) - data_size;
                di = (struct btrfs_dir_item *)ptr;
                btrfs_set_dir_data_len(leaf, di, size);
                data_ptr = ((unsigned long)(di + 1)) + name_len;
                write_extent_buffer(leaf, value, data_ptr, size);
                btrfs_mark_buffer_dirty(leaf);
        } else {
                /*
                 * Insert, and we had space for the xattr, so path->slots[0] is
                 * where our xattr dir_item is and btrfs_insert_xattr_item()
                 * filled it.
                 */
        }
out:
        btrfs_free_path(path);
        if (!ret)
                set_bit(BTRFS_INODE_COPY_EVERYTHING,
                        &BTRFS_I(inode)->runtime_flags);
        return ret;
}

/*
 * @value: "" makes the attribute to empty, NULL removes it
 */
int btrfs_setxattr_trans(struct inode *inode, const char *name,
                         const void *value, size_t size, int flags)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        int ret;

        trans = btrfs_start_transaction(root, 2);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = btrfs_setxattr(trans, inode, name, value, size, flags);
        if (ret)
                goto out;

        inode_inc_iversion(inode);
        inode->i_ctime = current_time(inode);
        ret = btrfs_update_inode(trans, root, inode);
        BUG_ON(ret);
out:
        btrfs_end_transaction(trans);
        return ret;
}

ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
        struct btrfs_key key;
        struct inode *inode = d_inode(dentry);
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_path *path;
        int ret = 0;
        size_t total_size = 0, size_left = size;

        /*
         * ok we want all objects associated with this id.
         * NOTE: we set key.offset = 0; because we want to start with the
         * first xattr that we find and walk forward
         */
        key.objectid = btrfs_ino(BTRFS_I(inode));
        key.type = BTRFS_XATTR_ITEM_KEY;
        key.offset = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
        path->reada = READA_FORWARD;

        /* search for our xattrs */
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto err;

        while (1) {
                struct extent_buffer *leaf;
                int slot;
                struct btrfs_dir_item *di;
                struct btrfs_key found_key;
                u32 item_size;
                u32 cur;

                leaf = path->nodes[0];
                slot = path->slots[0];

                /* this is where we start walking through the path */
                if (slot >= btrfs_header_nritems(leaf)) {
                        /*
                         * if we've reached the last slot in this leaf we need
                         * to go to the next leaf and reset everything
                         */
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto err;
                        else if (ret > 0)
                                break;
                        continue;
                }

                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                /* check to make sure this item is what we want */
                if (found_key.objectid != key.objectid)
                        break;
                if (found_key.type > BTRFS_XATTR_ITEM_KEY)
                        break;
                if (found_key.type < BTRFS_XATTR_ITEM_KEY)
                        goto next_item;

                di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
                item_size = btrfs_item_size_nr(leaf, slot);
                cur = 0;
                while (cur < item_size) {
                        u16 name_len = btrfs_dir_name_len(leaf, di);
                        u16 data_len = btrfs_dir_data_len(leaf, di);
                        u32 this_len = sizeof(*di) + name_len + data_len;
                        unsigned long name_ptr = (unsigned long)(di + 1);

                        total_size += name_len + 1;
                        /*
                         * We are just looking for how big our buffer needs to
                         * be.
                         */
                        if (!size)
                                goto next;

                        if (!buffer || (name_len + 1) > size_left) {
                                ret = -ERANGE;
                                goto err;
                        }

                        read_extent_buffer(leaf, buffer, name_ptr, name_len);
                        buffer[name_len] = '\0';

                        size_left -= name_len + 1;
                        buffer += name_len + 1;
next:
                        cur += this_len;
                        di = (struct btrfs_dir_item *)((char *)di + this_len);
                }
next_item:
                path->slots[0]++;
        }
        ret = total_size;

err:
        btrfs_free_path(path);

        return ret;
}

static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
                                   struct dentry *unused, struct inode *inode,
                                   const char *name, void *buffer, size_t size)
{
        name = xattr_full_name(handler, name);
        return btrfs_getxattr(inode, name, buffer, size);
}

static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
                                   struct dentry *unused, struct inode *inode,
                                   const char *name, const void *buffer,
                                   size_t size, int flags)
{
        name = xattr_full_name(handler, name);
        return btrfs_setxattr_trans(inode, name, buffer, size, flags);
}

static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
                                        struct dentry *unused, struct inode *inode,
                                        const char *name, const void *value,
                                        size_t size, int flags)
{
        int ret;
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        name = xattr_full_name(handler, name);
        ret = btrfs_validate_prop(name, value, size);
        if (ret)
                return ret;

        trans = btrfs_start_transaction(root, 2);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = btrfs_set_prop(trans, inode, name, value, size, flags);
        if (!ret) {
                inode_inc_iversion(inode);
                inode->i_ctime = current_time(inode);
                ret = btrfs_update_inode(trans, root, inode);
                BUG_ON(ret);
        }

        btrfs_end_transaction(trans);

        return ret;
}

static const struct xattr_handler btrfs_security_xattr_handler = {
        .prefix = XATTR_SECURITY_PREFIX,
        .get = btrfs_xattr_handler_get,
        .set = btrfs_xattr_handler_set,
};

static const struct xattr_handler btrfs_trusted_xattr_handler = {
        .prefix = XATTR_TRUSTED_PREFIX,
        .get = btrfs_xattr_handler_get,
        .set = btrfs_xattr_handler_set,
};

static const struct xattr_handler btrfs_user_xattr_handler = {
        .prefix = XATTR_USER_PREFIX,
        .get = btrfs_xattr_handler_get,
        .set = btrfs_xattr_handler_set,
};

static const struct xattr_handler btrfs_btrfs_xattr_handler = {
        .prefix = XATTR_BTRFS_PREFIX,
        .get = btrfs_xattr_handler_get,
        .set = btrfs_xattr_handler_set_prop,
};

const struct xattr_handler *btrfs_xattr_handlers[] = {
        &btrfs_security_xattr_handler,
#ifdef CONFIG_BTRFS_FS_POSIX_ACL
        &posix_acl_access_xattr_handler,
        &posix_acl_default_xattr_handler,
#endif
        &btrfs_trusted_xattr_handler,
        &btrfs_user_xattr_handler,
        &btrfs_btrfs_xattr_handler,
        NULL,
};

static int btrfs_initxattrs(struct inode *inode,
                            const struct xattr *xattr_array, void *fs_private)
{
        struct btrfs_trans_handle *trans = fs_private;
        const struct xattr *xattr;
        unsigned int nofs_flag;
        char *name;
        int err = 0;

        /*
         * We're holding a transaction handle, so use a NOFS memory allocation
         * context to avoid deadlock if reclaim happens.
         */
        nofs_flag = memalloc_nofs_save();
        for (xattr = xattr_array; xattr->name != NULL; xattr++) {
                name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
                               strlen(xattr->name) + 1, GFP_KERNEL);
                if (!name) {
                        err = -ENOMEM;
                        break;
                }
                strcpy(name, XATTR_SECURITY_PREFIX);
                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);
}