nfsd: release layout stid on setlease failure

From: Chris Mason <[email protected]>

commit 30d55c8aabb261bc3f427d6b9aae7ef6206063f9 upstream.

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).

---
 fs/nfsd/nfs4layouts.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

index 308214378fd3..84bb200e24ad 100644
@@ -242,9 +242,7 @@ nfsd4_alloc_layout_stateid(struct nfsd4_compound_state *cstate,
 	BUG_ON(!ls->ls_file);
 
 	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;
 	}
 

2.54.0

From: Jeff Layton <[email protected]>

commit 2090b05803faab8a9fa62fbff871007862cac1b7 upstream.

nfsd_vfs_write() and nfsd_commit() both call filemap_check_wb_err() to detect deferred writeback errors, but neither rotates the server's write verifier (nn->writeverf) when this check fails. Every other durable-storage-failure path in these functions calls commit_reset_write_verifier() before returning an error.

The missing rotation means clients holding UNSTABLE write data under the current verifier will COMMIT, receive the unchanged verifier back, and conclude their data is durable — silently dropping data that failed writeback. This violates the UNSTABLE+COMMIT durability contract (RFC 1813 §3.3.7, RFC 8881 §18.32).

Add commit_reset_write_verifier() calls at both filemap_check_wb_err() error sites, matching the pattern used by adjacent error paths in the same functions. The helper already filters -EAGAIN and -ESTALE internally, so the calls are unconditionally safe.

[ cel: 6.6.y predates the commit_reset_write_verifier() helper (v6.7);
open-coded nfsd_reset_write_verifier() and the reset tracepoint at both sites, matching the other reset paths in these functions ]

---
 fs/nfsd/vfs.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

index ae1f43eb515a..6658c92340f2 100644
@@ -1185,8 +1185,11 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 	nfsd_stats_io_write_add(nn, exp, *cnt);
 	fsnotify_modify(file);
 	host_err = filemap_check_wb_err(file->f_mapping, since);
-	if (host_err < 0)
+	if (host_err < 0) {
+		nfsd_reset_write_verifier(nn);
+		trace_nfsd_writeverf_reset(nn, rqstp, host_err);
 		goto out_nfserr;
+	}
 
 	if (stable && use_wgather) {
 		host_err = wait_for_concurrent_writes(file);

@@ -1330,6 +1333,10 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 			nfsd_copy_write_verifier(verf, nn);
 			err2 = filemap_check_wb_err(nf->nf_file->f_mapping,
 						    since);
+			if (err2 < 0) {
+				nfsd_reset_write_verifier(nn);
+				trace_nfsd_writeverf_reset(nn, rqstp, err2);
+			}
 			err = nfserrno(err2);
 			break;
 		case -EINVAL:

2.54.0

Queued the series for 6.6.y, thanks!

Thanks,
Sasha