On Tue, Jun 29, 2021 at 10:12 PM Gabriel Krisman Bertazi
<krisman@xxxxxxxxxxxxx> wrote:
>
> FAN_FS_ERROR will require fsid, but not necessarily require the
> filesystem to expose a file handle. Split those checks into different
> functions, so they can be used separately when setting up an event.
>
> While there, update a comment about tmpfs having 0 fsid, which is no
> longer true.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> Changes since v2:
> - FAN_ERROR -> FAN_FS_ERROR (Amir)
> - Update comment (Amir)
>
> Changes since v1:
> (Amir)
> - Sort hunks to simplify diff.
> Changes since RFC:
> (Amir)
> - Rename fanotify_check_path_fsid -> fanotify_test_fsid.
> - Use dentry directly instead of path.
> ---
> fs/notify/fanotify/fanotify_user.c | 27 ++++++++++++++++++---------
> 1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 68a53d3534f8..67b18dfe0025 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -1192,16 +1192,15 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
> return fd;
> }
>
> -/* Check if filesystem can encode a unique fid */
> -static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
> +static int fanotify_test_fsid(struct dentry *dentry, __kernel_fsid_t *fsid)
> {
> __kernel_fsid_t root_fsid;
> int err;
>
> /*
> - * Make sure path is not in filesystem with zero fsid (e.g. tmpfs).
> + * Make sure dentry is not of a filesystem with zero fsid (e.g. fuse).
> */
> - err = vfs_get_fsid(path->dentry, fsid);
> + err = vfs_get_fsid(dentry, fsid);
> if (err)
> return err;
>
> @@ -1209,10 +1208,10 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
> return -ENODEV;
>
> /*
> - * Make sure path is not inside a filesystem subvolume (e.g. btrfs)
> + * Make sure dentry is not of a filesystem subvolume (e.g. btrfs)
> * which uses a different fsid than sb root.
> */
> - err = vfs_get_fsid(path->dentry->d_sb->s_root, &root_fsid);
> + err = vfs_get_fsid(dentry->d_sb->s_root, &root_fsid);
> if (err)
> return err;
>
> @@ -1220,6 +1219,12 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
> root_fsid.val[1] != fsid->val[1])
> return -EXDEV;
>
> + return 0;
> +}
> +
> +/* Check if filesystem can encode a unique fid */
> +static int fanotify_test_fid(struct dentry *dentry)
> +{
> /*
> * We need to make sure that the file system supports at least
> * encoding a file handle so user can use name_to_handle_at() to
> @@ -1227,8 +1232,8 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
> * objects. However, name_to_handle_at() requires that the
> * filesystem also supports decoding file handles.
> */
> - if (!path->dentry->d_sb->s_export_op ||
> - !path->dentry->d_sb->s_export_op->fh_to_dentry)
> + if (!dentry->d_sb->s_export_op ||
> + !dentry->d_sb->s_export_op->fh_to_dentry)
> return -EOPNOTSUPP;
>
> return 0;
> @@ -1379,7 +1384,11 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
> }
>
> if (fid_mode) {
> - ret = fanotify_test_fid(&path, &__fsid);
> + ret = fanotify_test_fsid(path.dentry, &__fsid);
> + if (ret)
> + goto path_put_and_out;
> +
> + ret = fanotify_test_fid(path.dentry);
> if (ret)
> goto path_put_and_out;
>
> --
> 2.32.0
>
