On Fri, Nov 01, 2024 at 09:30:44AM -0400, Jeff Layton wrote:
> On Fri, 2024-11-01 at 09:18 -0400, Chuck Lever wrote:
> > On Fri, Nov 01, 2024 at 09:05:07AM -0400, Jeff Layton wrote:
> > > On Thu, 2024-10-31 at 09:40 -0400, cel@xxxxxxxxxx wrote:
> > > > From: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > > >
> > > > If an async COPY operation happens to be running when the server is
> > > > shut down, notify the requesting client that the copy has completed.
> > > >
> > > > Since the nfs4_client is going away, seems like this could introduce
> > > > some UAFs.
> > > >
> > > > Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> > > > ---
> > > > fs/nfsd/nfs4proc.c | 6 +++++-
> > > > 1 file changed, 5 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > > > index 4c964bce6bd7..51b3f85f3791 100644
> > > > --- a/fs/nfsd/nfs4proc.c
> > > > +++ b/fs/nfsd/nfs4proc.c
> > > > @@ -68,6 +68,8 @@ MODULE_PARM_DESC(nfsd4_ssc_umount_timeout,
> > > >
> > > > #define NFSDDBG_FACILITY NFSDDBG_PROC
> > > >
> > > > +static void nfsd4_send_cb_offload(struct nfsd4_copy *copy);
> > > > +
> > > > static u32 nfsd_attrmask[] = {
> > > > NFSD_WRITEABLE_ATTRS_WORD0,
> > > > NFSD_WRITEABLE_ATTRS_WORD1,
> > > > @@ -1381,8 +1383,10 @@ void nfsd4_shutdown_copy(struct nfs4_client *clp)
> > > > {
> > > > struct nfsd4_copy *copy;
> > > >
> > > > - while ((copy = nfsd4_get_copy(clp)) != NULL)
> > > > + while ((copy = nfsd4_get_copy(clp)) != NULL) {
> > > > nfsd4_stop_copy(copy);
> > > > + nfsd4_send_cb_offload(copy);
> > > > + }
> > >
> > > Not sure about a UAF, but it seems like NFS4ERR_DELAY returns might
> > > delay the client destruction for quite a while.
> >
> > The nfsd4_copy() is removed from the nfs4_client's async_copies
> > list, and the RPC proceeds in the background. It doesn't block the
> > destruction of the CLIENTID.
> >
> > But it might be a problem for the RPC logic to transmit the call
> > when there's no nfs4_client to dereference. I should probably
> > drop this patch and try a different approach.
>
>
> No, I think this will block the client shutdown. After
> nfsd4_shutdown_copy(), it calls nfsd4_shutdown_callback(), which does:
>
> flush_workqueue(clp->cl_callback_wq);
> nfsd41_cb_inflight_wait_complete(clp);
>
> So the CB_OFFLOAD workqueue jobs will run, and everything will wait for
> clp->cl_cb_inflight to go to 0. That won't happen until the CB_OFFLOAD
> jobs complete.
>
> No objection from me though if you see a better approach. Dropping this
> one for now seems reasonable.
There is no spec mandate (yet) for CB_OFFLOAD notification on
DESTROY_CLIENTID, so I'm dropping the patch for now.
> > > Maybe this CB_OFFLOAD shouldn't retry on DELAY?
Some logic can be added such that no retry is done. However, if the
client does not respond at all to the CB_OFFLOAD, NFSD's RPC timeout
is still 7 seconds.
We expect this will be exceptionally rare, though -- clients are
typically aware of ongoing COPY operations and generally won't try
to destroy a client ID where there is pending work that they care
about.
> > > > }
> > > > #ifdef CONFIG_NFSD_V4_2_INTER_SSC
> > > >
> > >
> > >
> > > --
> > > Jeff Layton <jlayton@xxxxxxxxxx>
> > >
> >
>
> --
> Jeff Layton <jlayton@xxxxxxxxxx>
>
--
Chuck Lever
