Re: [PATCH] nfsd: release layout stid on setlease failure

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2026-05-18 at 13:16 -0700, Chris Mason wrote:
> nfs4_alloc_stid() publishes the new stid into cl->cl_stateids via
> idr_alloc_cyclic() under cl_lock before returning to
> nfsd4_alloc_layout_stateid(). When nfsd4_layout_setlease() then
> fails, the error path frees the layout stateid directly with
> kmem_cache_free() without ever calling idr_remove(), leaving the
> IDR slot pointing at freed slab memory. Any subsequent IDR walker
> (states_show, client teardown) dereferences the dangling pointer.
> 
> The correct teardown for an IDR-published stid is nfs4_put_stid(),
> which removes the IDR slot under cl_lock, dispatches sc_free
> (nfsd4_free_layout_stateid) to release ls->ls_file via
> nfsd4_close_layout(), and drops the nfs4_file reference in its
> tail.
> 
> A second issue blocks that switch: nfsd4_free_layout_stateid()
> unconditionally inspects ls->ls_fence_work via
> delayed_work_pending() under ls_lock, but
> INIT_DELAYED_WORK(&ls->ls_fence_work, ...) currently runs only
> after the setlease call. On the setlease-failure path the
> destructor would touch an uninitialized delayed_work.
> 
>     nfsd4_alloc_layout_stateid()
>       nfs4_alloc_stid()           /* idr_alloc_cyclic under cl_lock */
>       nfsd4_layout_setlease()     /* fails */
>         nfs4_put_stid()
>           nfsd4_free_layout_stateid()
>             delayed_work_pending(&ls->ls_fence_work)  /* needs INIT */
>             nfsd4_close_layout()  /* nfsd_file_put(ls->ls_file) */
>           put_nfs4_file()
> 
> Fix by hoisting the ls_fenced / ls_fence_delay / INIT_DELAYED_WORK
> initialization above the nfsd4_layout_setlease() call, and replace
> the manual nfsd_file_put + put_nfs4_file + kmem_cache_free cleanup
> with a single nfs4_put_stid(stp).
> 
> Fixes: c5c707f96fc9 ("nfsd: implement pNFS layout recalls")
> Assisted-by: kres (claude-opus-4-7)
> Signed-off-by: Chris Mason <clm@meta.com>
> ---
>  fs/nfsd/nfs4layouts.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
> index 69e41105efdd..8e2929cffa7c 100644
> --- a/fs/nfsd/nfs4layouts.c
> +++ b/fs/nfsd/nfs4layouts.c
> @@ -264,10 +264,12 @@ nfsd4_alloc_layout_stateid(struct nfsd4_compound_state *cstate,
>  		ls->ls_file = find_any_file(fp);
>  	BUG_ON(!ls->ls_file);
>  
> +	ls->ls_fenced = false;
> +	ls->ls_fence_delay = 0;
> +	INIT_DELAYED_WORK(&ls->ls_fence_work, nfsd4_layout_fence_worker);
> +
>  	if (nfsd4_layout_setlease(ls)) {
> -		nfsd_file_put(ls->ls_file);
> -		put_nfs4_file(fp);
> -		kmem_cache_free(nfs4_layout_stateid_cache, ls);
> +		nfs4_put_stid(stp);
>  		return NULL;
>  	}
>  
> @@ -280,10 +282,6 @@ nfsd4_alloc_layout_stateid(struct nfsd4_compound_state *cstate,
>  	list_add(&ls->ls_perfile, &fp->fi_lo_states);
>  	spin_unlock(&fp->fi_lock);
>  
> -	ls->ls_fenced = false;
> -	ls->ls_fence_delay = 0;
> -	INIT_DELAYED_WORK(&ls->ls_fence_work, nfsd4_layout_fence_worker);
> -
>  	trace_nfsd_layoutstate_alloc(&ls->ls_stid.sc_stateid);
>  	return ls;
>  }

Reviewed-by: Jeff Layton <jlayton@kernel.org>