Re: [Virtio-fs] [PATCH 1/3] virtiofsd: Don't allow empty paths in lookup_name()

[Vivek Goyal]

On Fri, Mar 12, 2021 at 03:10:01PM +0100, Greg Kurz wrote:
> When passed an empty filename, lookup_name() returns the inode of
> the parent directory, unless the parent is the root in which case
> the st_dev doesn't match and lo_find() returns NULL. This is
> because lookup_name() passes AT_EMPTY_PATH down to fstatat() or
> statx().
> 
> This behavior doesn't quite make sense because users of lookup_name()
> then pass the name to unlinkat(), renameat() or renameat2(), all of
> which will always fail on empty names.
> 
> Drop AT_EMPTY_PATH from the flags in lookup_name() so that it has
> the consistent behavior of "returning an existing child inode or
> NULL" for all directories.
> 
> Signed-off-by: Greg Kurz <groug@kaod.org>

Looks good to me. Can't think in what cases fuse will need to pass in
empty path for lookup.

Reviewed-by: Vivek Goyal <vgoyal@redhat.com>

Vivek
> ---
>  tools/virtiofsd/passthrough_ll.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/tools/virtiofsd/passthrough_ll.c 
> b/tools/virtiofsd/passthrough_ll.c
> index fc7e1b1e8e2b..27a6c636dcaf 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -1308,8 +1308,7 @@ static struct lo_inode *lookup_name(fuse_req_t req, 
> fuse_ino_t parent,
>          return NULL;
>      }
>  
> -    res = do_statx(lo, dir->fd, name, &attr,
> -                   AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW, &mnt_id);
> +    res = do_statx(lo, dir->fd, name, &attr, AT_SYMLINK_NOFOLLOW, &mnt_id);
>      lo_inode_put(lo, &dir);
>      if (res == -1) {
>          return NULL;
> -- 
> 2.26.2
> 
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