Re: [PATCH RFC v6 05/16] fuse: make args->in_args[0] to be always the header

[Miklos Szeredi <miklos@szeredi.hu>]

On Fri, 22 Nov 2024 at 00:44, Bernd Schubert <bschubert@ddn.com> wrote:

> diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
> index 12ef91d170bb3091ac35a33d2b9dc38330b00948..e459b8134ccb089f971bebf8da1f7fc5199c1271 100644
> --- a/fs/fuse/dax.c
> +++ b/fs/fuse/dax.c
> @@ -237,14 +237,17 @@ static int fuse_send_removemapping(struct inode *inode,
>         struct fuse_inode *fi = get_fuse_inode(inode);
>         struct fuse_mount *fm = get_fuse_mount(inode);
>         FUSE_ARGS(args);
> +       struct fuse_zero_in zero_arg;

I'd move this to global scope (i.e. just a single instance for all
uses) and rename to zero_header.

> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index fd8898b0c1cca4d117982d5208d78078472b0dfb..6cb45b5332c45f322e9163469ffd114cbc07dc4f 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1053,6 +1053,19 @@ static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
>
>         for (i = 0; !err && i < numargs; i++)  {
>                 struct fuse_arg *arg = &args[i];
> +
> +               /* zero headers */
> +               if (arg->size == 0) {
> +                       if (WARN_ON_ONCE(i != 0)) {
> +                               if (cs->req)
> +                                       pr_err_once(
> +                                               "fuse: zero size header in opcode %d\n",
> +                                               cs->req->in.h.opcode);
> +                               return -EINVAL;
> +                       }

Just keep the WARN_ON_ONCE() and drop everything else, including
return -EINVAL.  The same thing should happen without the arg->size ==
0 check.

Thanks,
Miklos