RE: [PATCH v6 2/3] btrfs: Add unprivileged ioctl which returns subvolume's ROOT_REF
> -Original Message-
> From: linux-btrfs-ow...@vger.kernel.org
> [mailto:linux-btrfs-ow...@vger.kernel.org] On Behalf Of Tomohiro Misono
> Sent: Friday, May 18, 2018 10:55 AM
> To: linux-btrfs@vger.kernel.org
> Subject: [PATCH v6 2/3] btrfs: Add unprivileged ioctl which returns
> subvolume's ROOT_REF
>
> Add unprivileged ioctl BTRFS_IOC_GET_SUBVOL_ROOTREF which returns ROOT_REF
> information of the subvolume containing this inode
> except the subvolume name (this is because to prevent potential name leak).
> The subvolume name will be gained by user version of
> ino_lookup ioctl (BTRFS_IOC_INO_LOOKUP_USER) which also performs permission
> check.
>
> The min id of root ref's subvolume to be searched is specified by @min_id in
> struct btrfs_ioctl_get_subvol_rootref_args. After the search
> ends, @min_id is set to the last searched root ref's subvolid + 1. Also, if
> there are more root refs than
> BTRFS_MAX_ROOTREF_BUFFER_NUM, -EOVERFLOW is returned. Therefore the caller
> can just call this ioctl again without changing the
> argument to continue search.
>
> Reviewed-by: Qu Wenruo
> Signed-off-by: Tomohiro Misono
> ---
> v4 -> v5
> - Update error handling of btrfs_next_leaf() to cover all cases
> - Use btrfs_next_item() to reduce the call of btrfs_search_slot()
>
> fs/btrfs/ioctl.c | 102
> +
> include/uapi/linux/btrfs.h | 16 +++
> 2 files changed, 118 insertions(+)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index
> 31af6e91c614..463ddedd90da 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2365,6 +2365,106 @@ static noinline int
> btrfs_ioctl_get_subvol_info(struct file *file,
> return ret;
> }
>
> +/*
> + * Return ROOT_REF information of the subvolume containing this inode
> + * except the subvolume name.
> + */
> +static noinline int btrfs_ioctl_get_subvol_rootref(struct file *file,
> +void __user *argp)
> +{
> + struct btrfs_ioctl_get_subvol_rootref_args *rootrefs;
> + struct btrfs_root_ref *rref;
> + struct btrfs_root *root;
> + struct btrfs_path *path;
> + struct btrfs_key key;
> +
> + struct extent_buffer *l;
> + int slot;
> +
> + struct inode *inode;
> + int ret;
> + u64 objectid;
> + u8 found;
> +
> + path = btrfs_alloc_path();
> + if (!path)
> + return -ENOMEM;
> +
> + rootrefs = memdup_user(argp, sizeof(*rootrefs));
> + if (!rootrefs) {
> + btrfs_free_path(path);
> + return -ENOMEM;
> + }
> +
> + inode = file_inode(file);
> + root = BTRFS_I(inode)->root->fs_info->tree_root;
> + objectid = BTRFS_I(inode)->root->root_key.objectid;
> +
> + key.objectid = objectid;
> + key.type = BTRFS_ROOT_REF_KEY;
> + key.offset = rootrefs->min_id;
> + found = 0;
> +
> + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
> + if (ret < 0) {
> + goto out;
> + } else if (path->slots[0] >=
> + btrfs_header_nritems(path->nodes[0])) {
> + ret = btrfs_next_leaf(root, path);
> + if (ret < 0) {
> + goto out;
> + } else if (ret > 0) {
> + ret = -EUCLEAN;
> + goto out;
> + }
> + }
> + while (1) {
> + l = path->nodes[0];
> + slot = path->slots[0];
> +
> + btrfs_item_key_to_cpu(l, &key, slot);
> + if (key.objectid != objectid ||
> + key.type != BTRFS_ROOT_REF_KEY) {
> + ret = 0;
> + goto out;
> + }
> +
> + if (found == BTRFS_MAX_ROOTREF_BUFFER_NUM) {
> + ret = -EOVERFLOW;
> + goto out;
> + }
> +
> + rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref);
> + rootrefs->rootref[found].subvolid = key.offset;
> + rootrefs->rootref[found].dirid =
> + btrfs_root_ref_dirid(l, rref);
> + found++;
> +
> + ret = btrfs_next_item(root, path);
> + if (ret < 0) {
> + goto out;
> + } else if (ret > 0) {
> + ret = -EUCLEAN;
> + goto out;
> + }
> + }
> +
> +out:
> + if (!ret || ret == -EOVERFLOW) {
> + rootrefs->num_items = found;
> + /* update min_id for next search */
> + if (found)
> + rootrefs->min_id =
> + rootrefs->rootref[found - 1].subvolid + 1;
> + if (copy_to_user(argp, rootrefs, sizeof(*rootrefs)))
> + ret = -EFAULT;
> + }
> +
> + btrfs_free_path(path);
> + kfree(rootrefs);
> + return ret;
> +}
> +
> static noinline int btrfs_ioctl_snap_destroy(struct file *file,
>
RE: [PATCH v6 2/3] btrfs: Add unprivileged ioctl which returns subvolume's ROOT_REF
> -Original Message-
> From: linux-btrfs-ow...@vger.kernel.org
> [mailto:linux-btrfs-ow...@vger.kernel.org] On Behalf Of Tomohiro Misono
> Sent: Friday, May 18, 2018 10:55 AM
> To: linux-btrfs@vger.kernel.org
> Subject: [PATCH v6 2/3] btrfs: Add unprivileged ioctl which returns
> subvolume's ROOT_REF
>
> Add unprivileged ioctl BTRFS_IOC_GET_SUBVOL_ROOTREF which returns ROOT_REF
> information of the subvolume containing this inode
> except the subvolume name (this is because to prevent potential name leak).
> The subvolume name will be gained by user version of
> ino_lookup ioctl (BTRFS_IOC_INO_LOOKUP_USER) which also performs permission
> check.
>
> The min id of root ref's subvolume to be searched is specified by @min_id in
> struct btrfs_ioctl_get_subvol_rootref_args. After the search
> ends, @min_id is set to the last searched root ref's subvolid + 1. Also, if
> there are more root refs than
> BTRFS_MAX_ROOTREF_BUFFER_NUM, -EOVERFLOW is returned. Therefore the caller
> can just call this ioctl again without changing the
> argument to continue search.
>
> Reviewed-by: Qu Wenruo
> Signed-off-by: Tomohiro Misono
> ---
> v4 -> v5
> - Update error handling of btrfs_next_leaf() to cover all cases
> - Use btrfs_next_item() to reduce the call of btrfs_search_slot()
>
> fs/btrfs/ioctl.c | 102
> +
> include/uapi/linux/btrfs.h | 16 +++
> 2 files changed, 118 insertions(+)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index
> 31af6e91c614..463ddedd90da 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2365,6 +2365,106 @@ static noinline int
> btrfs_ioctl_get_subvol_info(struct file *file,
> return ret;
> }
>
> +/*
> + * Return ROOT_REF information of the subvolume containing this inode
> + * except the subvolume name.
> + */
> +static noinline int btrfs_ioctl_get_subvol_rootref(struct file *file,
> +void __user *argp)
> +{
> + struct btrfs_ioctl_get_subvol_rootref_args *rootrefs;
> + struct btrfs_root_ref *rref;
> + struct btrfs_root *root;
> + struct btrfs_path *path;
> + struct btrfs_key key;
> +
> + struct extent_buffer *l;
> + int slot;
> +
> + struct inode *inode;
> + int ret;
> + u64 objectid;
> + u8 found;
> +
> + path = btrfs_alloc_path();
> + if (!path)
> + return -ENOMEM;
> +
> + rootrefs = memdup_user(argp, sizeof(*rootrefs));
> + if (!rootrefs) {
> + btrfs_free_path(path);
> + return -ENOMEM;
> + }
> +
> + inode = file_inode(file);
> + root = BTRFS_I(inode)->root->fs_info->tree_root;
> + objectid = BTRFS_I(inode)->root->root_key.objectid;
> +
> + key.objectid = objectid;
> + key.type = BTRFS_ROOT_REF_KEY;
> + key.offset = rootrefs->min_id;
> + found = 0;
> +
> + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
> + if (ret < 0) {
> + goto out;
> + } else if (path->slots[0] >=
> + btrfs_header_nritems(path->nodes[0])) {
> + ret = btrfs_next_leaf(root, path);
> + if (ret < 0) {
> + goto out;
> + } else if (ret > 0) {
> + ret = -EUCLEAN;
> + goto out;
> + }
> + }
> + while (1) {
> + l = path->nodes[0];
> + slot = path->slots[0];
> +
> + btrfs_item_key_to_cpu(l, &key, slot);
> + if (key.objectid != objectid ||
> + key.type != BTRFS_ROOT_REF_KEY) {
> + ret = 0;
> + goto out;
> + }
> +
> + if (found == BTRFS_MAX_ROOTREF_BUFFER_NUM) {
> + ret = -EOVERFLOW;
> + goto out;
> + }
> +
> + rref = btrfs_item_ptr(l, slot, struct btrfs_root_ref);
> + rootrefs->rootref[found].subvolid = key.offset;
> + rootrefs->rootref[found].dirid =
> + btrfs_root_ref_dirid(l, rref);
> + found++;
> +
> + ret = btrfs_next_item(root, path);
> + if (ret < 0) {
> + goto out;
> + } else if (ret > 0) {
> + ret = -EUCLEAN;
> + goto out;
> + }
> + }
> +
> +out:
> + if (!ret || ret == -EOVERFLOW) {
> + rootrefs->num_items = found;
> + /* update min_id for next search */
> + if (found)
> + rootrefs->min_id =
> + rootrefs->rootref[found - 1].subvolid + 1;
> + if (copy_to_user(argp, rootrefs, sizeof(*rootrefs)))
> + ret = -EFAULT;
> + }
> +
> + btrfs_free_path(path);
> + kfree(rootrefs);
> + return ret;
> +}
> +
> static noinline int btrfs_ioctl_snap_destroy(struct file *file,
>
