diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index be9b3f39183cb976e2fb14544888b57a77c8d40e..d29992f7dc6356b2de853f5dde76cebedc3e30d0 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2341,6 +2341,165 @@ static noinline int btrfs_search_path_in_tree(struct btrfs_fs_info *info, return ret; } +static int btrfs_search_path_in_tree_user(struct inode *inode, + struct btrfs_ioctl_ino_lookup_user_args *args) +{ + struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info; + struct super_block *sb = inode->i_sb; + struct btrfs_key upper_limit = BTRFS_I(inode)->location; + u64 treeid = BTRFS_I(inode)->root->root_key.objectid; + u64 dirid = args->dirid; + unsigned long item_off; + unsigned long item_len; + struct btrfs_inode_ref *iref; + struct btrfs_root_ref *rref; + struct btrfs_root *root; + struct btrfs_path *path; + struct btrfs_key key, key2; + struct extent_buffer *leaf; + struct inode *temp_inode; + char *ptr; + int slot; + int len; + int total_len = 0; + int ret; + + path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; + + /* + * If the bottom subvolume does not exist directly under upper_limit, + * construct the path in from the bottom up. + */ + if (dirid != upper_limit.objectid) { + ptr = &args->path[BTRFS_INO_LOOKUP_USER_PATH_MAX - 1]; + + key.objectid = treeid; + key.type = BTRFS_ROOT_ITEM_KEY; + key.offset = (u64)-1; + root = btrfs_read_fs_root_no_name(fs_info, &key); + if (IS_ERR(root)) { + ret = PTR_ERR(root); + goto out; + } + + key.objectid = dirid; + key.type = BTRFS_INODE_REF_KEY; + key.offset = (u64)-1; + while (1) { + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + if (ret < 0) { + goto out; + } else if (ret > 0) { + ret = btrfs_previous_item(root, path, dirid, + BTRFS_INODE_REF_KEY); + if (ret < 0) { + goto out; + } else if (ret > 0) { + ret = -ENOENT; + goto out; + } + } + + leaf = path->nodes[0]; + slot = path->slots[0]; + btrfs_item_key_to_cpu(leaf, &key, slot); + + iref = btrfs_item_ptr(leaf, slot, struct btrfs_inode_ref); + len = btrfs_inode_ref_name_len(leaf, iref); + ptr -= len + 1; + total_len += len + 1; + if (ptr < args->path) { + ret = -ENAMETOOLONG; + goto out; + } + + *(ptr + len) = '/'; + read_extent_buffer(leaf, ptr, + (unsigned long)(iref + 1), len); + + /* Check the read+exec permission of this directory */ + ret = btrfs_previous_item(root, path, dirid, + BTRFS_INODE_ITEM_KEY); + if (ret < 0) { + goto out; + } else if (ret > 0) { + ret = -ENOENT; + goto out; + } + + leaf = path->nodes[0]; + slot = path->slots[0]; + btrfs_item_key_to_cpu(leaf, &key2, slot); + if (key2.objectid != dirid) { + ret = -ENOENT; + goto out; + } + + temp_inode = btrfs_iget(sb, &key2, root, NULL); + ret = inode_permission(temp_inode, MAY_READ | MAY_EXEC); + iput(temp_inode); + if (ret) { + ret = -EACCES; + goto out; + } + + if (key.offset == upper_limit.objectid) + break; + if (key.objectid == BTRFS_FIRST_FREE_OBJECTID) { + ret = -EACCES; + goto out; + } + + btrfs_release_path(path); + key.objectid = key.offset; + key.offset = (u64)-1; + dirid = key.objectid; + } + + memmove(args->path, ptr, total_len); + args->path[total_len] = '\0'; + btrfs_release_path(path); + } + + /* Get the bottom subvolume's name from ROOT_REF */ + root = fs_info->tree_root; + key.objectid = treeid; + key.type = BTRFS_ROOT_REF_KEY; + key.offset = args->treeid; + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + if (ret < 0) { + goto out; + } else if (ret > 0) { + ret = -ENOENT; + goto out; + } + + leaf = path->nodes[0]; + slot = path->slots[0]; + btrfs_item_key_to_cpu(leaf, &key, slot); + + item_off = btrfs_item_ptr_offset(leaf, slot); + item_len = btrfs_item_size_nr(leaf, slot); + /* Check if dirid in ROOT_REF corresponds to passed dirid */ + rref = btrfs_item_ptr(leaf, slot, struct btrfs_root_ref); + if (args->dirid != btrfs_root_ref_dirid(leaf, rref)) { + ret = -EINVAL; + goto out; + } + + /* Copy subvolume's name */ + item_off += sizeof(struct btrfs_root_ref); + item_len -= sizeof(struct btrfs_root_ref); + read_extent_buffer(leaf, args->name, item_off, item_len); + args->name[item_len] = 0; + +out: + btrfs_free_path(path); + return ret; +} + static noinline int btrfs_ioctl_ino_lookup(struct file *file, void __user *argp) { @@ -2383,6 +2542,49 @@ static noinline int btrfs_ioctl_ino_lookup(struct file *file, return ret; } +/* + * Version of ino_lookup ioctl (unprivileged) + * + * The main differences from ino_lookup ioctl are: + * + * 1. Read + Exec permission will be checked using inode_permission() during + * path construction. -EACCES will be returned in case of failure. + * 2. Path construction will be stopped at the inode number which corresponds + * to the fd with which this ioctl is called. If constructed path does not + * exist under fd's inode, -EACCES will be returned. + * 3. The name of bottom subvolume is also searched and filled. + */ +static int btrfs_ioctl_ino_lookup_user(struct file *file, void __user *argp) +{ + struct btrfs_ioctl_ino_lookup_user_args *args; + struct inode *inode; + int ret; + + args = memdup_user(argp, sizeof(*args)); + if (IS_ERR(args)) + return PTR_ERR(args); + + inode = file_inode(file); + + if (args->dirid == BTRFS_FIRST_FREE_OBJECTID && + BTRFS_I(inode)->location.objectid != BTRFS_FIRST_FREE_OBJECTID) { + /* + * The subvolume does not exist under fd with which this is + * called + */ + kfree(args); + return -EACCES; + } + + ret = btrfs_search_path_in_tree_user(inode, args); + + if (ret == 0 && copy_to_user(argp, args, sizeof(*args))) + ret = -EFAULT; + + kfree(args); + return ret; +} + /* Get the subvolume information in BTRFS_ROOT_ITEM and BTRFS_ROOT_BACKREF */ static int btrfs_ioctl_get_subvol_info(struct file *file, void __user *argp) { @@ -5765,6 +5967,8 @@ long btrfs_ioctl(struct file *file, unsigned int return btrfs_ioctl_get_subvol_info(file, argp); case BTRFS_IOC_GET_SUBVOL_ROOTREF: return btrfs_ioctl_get_subvol_rootref(file, argp); + case BTRFS_IOC_INO_LOOKUP_USER: + return btrfs_ioctl_ino_lookup_user(file, argp); } return -ENOTTY; diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h index f90d104782359c60f1821bc741728ce6a183ce14..5ca1d21fc4a7a85db1bd9c8cf15e5f334d8e59d6 100644 --- a/include/uapi/linux/btrfs.h +++ b/include/uapi/linux/btrfs.h @@ -422,6 +422,21 @@ struct btrfs_ioctl_ino_lookup_args { char name[BTRFS_INO_LOOKUP_PATH_MAX]; }; +#define BTRFS_INO_LOOKUP_USER_PATH_MAX (4080 - BTRFS_VOL_NAME_MAX - 1) +struct btrfs_ioctl_ino_lookup_user_args { + /* in, inode number containing the subvolume of 'subvolid' */ + __u64 dirid; + /* in */ + __u64 treeid; + /* out, name of the subvolume of 'treeid' */ + char name[BTRFS_VOL_NAME_MAX + 1]; + /* + * out, constructed path from the directory with which the ioctl is + * called to dirid + */ + char path[BTRFS_INO_LOOKUP_USER_PATH_MAX]; +}; + /* Search criteria for the btrfs SEARCH ioctl family. */ struct btrfs_ioctl_search_key { /* @@ -923,5 +938,7 @@ enum btrfs_err_code { struct btrfs_ioctl_get_subvol_info_args) #define BTRFS_IOC_GET_SUBVOL_ROOTREF _IOWR(BTRFS_IOCTL_MAGIC, 61, \ struct btrfs_ioctl_get_subvol_rootref_args) +#define BTRFS_IOC_INO_LOOKUP_USER _IOWR(BTRFS_IOCTL_MAGIC, 62, \ + struct btrfs_ioctl_ino_lookup_user_args) #endif /* _UAPI_LINUX_BTRFS_H */