[PATCH v3 3/5] nfsd: Never cache a COMPOUND when the SEQUENCE operation fails

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

RFC 8881 normatively mandates that operations where the initial
SEQUENCE operation in a compound fails must not modify the slot's
replay cache.

nfsd4_cache_this() doesn't prevent such caching.

Fixes: 468de9e54a90 ("nfsd41: expand solo sequence check")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfs4state.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index c9053ef4d79f..7b80f00fb32c 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3477,16 +3477,26 @@ gen_callback(struct nfs4_client *clp, struct nfsd4_setclientid *se, struct svc_r
 }
 
 /*
- * Cache a reply. nfsd4_check_resp_size() has bounded the cache size.
+ * Maybe cache a reply. nfsd4_check_resp_size() has bounded the cache size.
  */
 static void
 nfsd4_store_cache_entry(struct nfsd4_compoundres *resp)
 {
-	struct xdr_buf *buf = resp->xdr->buf;
+	struct nfsd4_compoundargs *args = resp->rqstp->rq_argp;
 	struct nfsd4_slot *slot = resp->cstate.slot;
+	struct xdr_buf *buf = resp->xdr->buf;
 	unsigned int base;
 
-	dprintk("--> %s slot %p\n", __func__, slot);
+	/*
+	 * RFC 5661 Section 2.10.6.1.2:
+	 *
+	 * Any time SEQUENCE ... returns an error ... [t]he replier MUST NOT
+	 * modify the reply cache entry for the slot whenever an error is
+	 * returned from SEQUENCE ...
+	 */
+	if (resp->opcnt == 1 && args->ops[0].opnum == OP_SEQUENCE &&
+	    resp->cstate.status != nfs_ok)
+		return;
 
 	slot->sl_flags |= NFSD4_SLOT_INITIALIZED;
 	slot->sl_opcnt = resp->opcnt;
-- 
2.51.0