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NFSD: CREATE_SESSION must never cache NFS4ERR_DELAY replies

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There are one or two cases where CREATE_SESSION returns
NFS4ERR_DELAY in order to force the client to wait a bit and try
CREATE_SESSION again. However, after commit e4469c6cc6 ("NFSD: Fix
the NFSv4.1 CREATE_SESSION operation"), NFSD caches that response in
the CREATE_SESSION slot. Thus, when the client resends the
CREATE_SESSION, the server always returns the cached NFS4ERR_DELAY
response rather than actually executing the request and properly
recording its outcome. This blocks the client from making further
progress.

RFC 8881 Section 15.1.1.3 says:
> If NFS4ERR_DELAY is returned on an operation other than SEQUENCE
> that validly appears as the first operation of a request ... [t]he
> request can be retried in full without modification. In this case
> as well, the replier MUST avoid returning a response containing
> NFS4ERR_DELAY as the response to an initial operation of a request
> solely on the basis of its presence in the reply cache.

Neither the original NFSD code nor the discussion in section 18.36.4
refer explicitly to this important requirement, so I missed it.

Note also that not only must the server not cache NFS4ERR_DELAY, but
it has to not advance the CREATE_SESSION slot sequence number so
that it can properly recognize and accept the client's retry.

Reported-by: Dai Ngo <dai.ngo@oracle.com>
Fixes: e4469c6cc6 ("NFSD: Fix the NFSv4.1 CREATE_SESSION operation")
Tested-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever 2024-03-26 17:00:20 -04:00
parent 6978bd6a91
commit 99dc2ef039
1 changed files with 25 additions and 11 deletions
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36
fs/nfsd/nfs4state.c
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@ -3831,15 +3831,20 @@ nfsd4_create_session(struct svc_rqst *rqstp,
else
cs_slot = &unconf->cl_cs_slot;
status = check_slot_seqid(cr_ses->seqid, cs_slot->sl_seqid, 0);
if (status) {
if (status == nfserr_replay_cache) {
status = nfsd4_replay_create_session(cr_ses, cs_slot);
goto out_free_conn;
}
switch (status) {
case nfs_ok:
cs_slot->sl_seqid++;
cr_ses->seqid = cs_slot->sl_seqid;
break;
case nfserr_replay_cache:
status = nfsd4_replay_create_session(cr_ses, cs_slot);
fallthrough;
case nfserr_jukebox:
/* The server MUST NOT cache NFS4ERR_DELAY */
goto out_free_conn;
default:
goto out_cache_error;
}
cs_slot->sl_seqid++;
cr_ses->seqid = cs_slot->sl_seqid;
/* RFC 8881 Section 18.36.4 Phase 3: Client ID confirmation. */
if (conf) {
@ -3859,10 +3864,8 @@ nfsd4_create_session(struct svc_rqst *rqstp,
old = find_confirmed_client_by_name(&unconf->cl_name, nn);
if (old) {
status = mark_client_expired_locked(old);
if (status) {
old = NULL;
goto out_cache_error;
}
if (status)
goto out_expired_error;
trace_nfsd_clid_replaced(&old->cl_clientid);
}
move_to_confirmed(unconf);
@ -3894,6 +3897,17 @@ nfsd4_create_session(struct svc_rqst *rqstp,
expire_client(old);
return status;
out_expired_error:
old = NULL;
/*
* Revert the slot seq_nr change so the server will process
* the client's resend instead of returning a cached response.
*/
if (status == nfserr_jukebox) {
cs_slot->sl_seqid--;
cr_ses->seqid = cs_slot->sl_seqid;
goto out_free_conn;
}
out_cache_error:
nfsd4_cache_create_session(cr_ses, cs_slot, status);
out_free_conn: