[Virtio-fs] [PATCH] virtiofsd: fix double fuse_mbuf_iter_advance when do_removemapping

[Catherine Ho]

Hi Peng

On Thu, 5 Dec 2019 at 17:19, Peng Tao <tao.peng at linux.alibaba.com> wrote:
>
> On 2019/12/5 17:01, Catherine Ho wrote:
> > Commit 8e92b1fc98f7 ("DAX: virtiofsd: make FUSE_REMOVEMAPPING support
> > multiple entries") forgot to remove one fuse_mbuf_iter_advance in
> > do_removemapping.
> No, we do need to advance twice. One for fuse_removemapping_in, another
> for an array of fuse_removemapping_one.
>
But seems it advances for 3 times. What I mean is the 2nd advance of *one*
is pointless.
Please see [1] [2]
[1]https://gitlab.com/virtio-fs/qemu/blob/virtio-fs-dev/contrib/virtiofsd/fuse_lowlevel.c#L1888
[2]https://gitlab.com/virtio-fs/qemu/blob/virtio-fs-dev/contrib/virtiofsd/fuse_lowlevel.c#L1896

Best Regards
Catherine
> >
> > Without this patch, virtiofsd will report:
> > [ID: 00000123] do_removemapping: invalid in, expected 1 * 16, has 60 - 60
> > [ID: 00000123]    unique: 232, error: -22 (Invalid argument), outsize: 16
> >
> What kernel version are you using? It appears that the remove mapping
> request does not container a proper fuse_removemapping_one struct.
>
> > Fixes: 8e92b1fc98f7 ("DAX: virtiofsd: make FUSE_REMOVEMAPPING support multiple entries")
> > Cc: Peng Tao <tao.peng at linux.alibaba.com>
> > Signed-off-by: Catherine Ho <catherine.hecx at gmail.com>
> > ---
> >   contrib/virtiofsd/fuse_lowlevel.c | 8 --------
> >   1 file changed, 8 deletions(-)
> >
> > diff --git a/contrib/virtiofsd/fuse_lowlevel.c b/contrib/virtiofsd/fuse_lowlevel.c
> > index bde66c72c3..752e7d97b9 100644
> > --- a/contrib/virtiofsd/fuse_lowlevel.c
> > +++ b/contrib/virtiofsd/fuse_lowlevel.c
> > @@ -1894,14 +1894,6 @@ static void do_removemapping(fuse_req_t req, fuse_ino_t nodeid,
> >               return;
> >       }
> >
> > -     one = fuse_mbuf_iter_advance(iter, sizeof(*one));
> > -     if (!one) {
> > -             fuse_log(FUSE_LOG_ERR, "do_removemapping: invalid in, expected %d * %ld, has %ld - %ld\n",
> > -                      arg->count, sizeof(*one), iter->size, iter->pos);
> > -             fuse_reply_err(req, EINVAL);
> > -             return;
> > -     }
> > -
> >       if (req->se->op.removemapping)
> >               req->se->op.removemapping(req, req->se, nodeid, arg->count, one);
> The patch is wrong itself, as `one` is not assigned here.
>