--- sys/fs/nfs/nfs_commonsubs.c.bs4	2021-04-05 23:10:49.961997000 -0700
+++ sys/fs/nfs/nfs_commonsubs.c	2021-04-05 23:27:27.566277000 -0700
@@ -4614,12 +4614,13 @@ nfsmout:
  * Handle an NFSv4.1 Sequence request for the session.
  * If reply != NULL, use it to return the cached reply, as required.
  * The client gets a cached reply via this call for callbacks, however the
- * server gets a cached reply via the nfsv4_seqsess_cachereply() call.
+ * server gets a cached reply via the nfsv4_seqsess_cacherep() call.
  */
 int
 nfsv4_seqsession(uint32_t seqid, uint32_t slotid, uint32_t highslot,
     struct nfsslot *slots, struct mbuf **reply, uint16_t maxslot)
 {
+	struct mbuf *m;
 	int error;
 
 	error = 0;
@@ -4633,8 +4634,21 @@ nfsv4_seqsession(uint32_t seqid, uint32_t slotid, uint
 			error = NFSERR_DELAY;
 		else if (slots[slotid].nfssl_reply != NULL) {
 			if (reply != NULL) {
-				*reply = slots[slotid].nfssl_reply;
-				slots[slotid].nfssl_reply = NULL;
+				m = m_copym(slots[slotid].nfssl_reply, 0,
+				    M_COPYALL, M_NOWAIT);
+				if (m != NULL)
+					*reply = m;
+				else {
+					/*
+					 * Multiple retries + m_copym()
+					 * failing will be extremely rare,
+					 * so using the cached reply is
+					 * highly unlikely to cause a cached
+					 * reply miss for subsequent retries.
+					 */
+					*reply = slots[slotid].nfssl_reply;
+					slots[slotid].nfssl_reply = NULL;
+				}
 			}
 			slots[slotid].nfssl_inprog = 1;
 			error = NFSERR_REPLYFROMCACHE;
@@ -4662,10 +4676,27 @@ void
 nfsv4_seqsess_cacherep(uint32_t slotid, struct nfsslot *slots, int repstat,
    struct mbuf **rep)
 {
+	struct mbuf *m;
 
 	if (repstat == NFSERR_REPLYFROMCACHE) {
-		*rep = slots[slotid].nfssl_reply;
-		slots[slotid].nfssl_reply = NULL;
+		if (slots[slotid].nfssl_reply != NULL) {
+			m = m_copym(slots[slotid].nfssl_reply, 0, M_COPYALL,
+			    M_NOWAIT);
+			if (m != NULL)
+				*rep = m;
+			else {
+				/*
+				 * Multiple retries + m_copym()
+				 * failing will be extremely rare,
+				 * so using the cached reply is
+				 * highly unlikely to cause a cached
+				 * reply miss for subsequent retries.
+				 */
+				*rep = slots[slotid].nfssl_reply;
+				slots[slotid].nfssl_reply = NULL;
+			}
+		} else
+			*rep = NULL;
 	} else {
 		if (slots[slotid].nfssl_reply != NULL)
 			m_freem(slots[slotid].nfssl_reply);