On May 2, 2023, at 7:01 AM, Jiri Slaby [off-list ref] wrote:

On 08. 01. 23, 17:31, Chuck Lever wrote:

quoted

From: Chuck Lever <redacted>
To navigate around the space that svcauth_gss_accept() reserves
for the RPC payload body length and sequence number fields,
svcauth_gss_release() does a little dance with the reply's
accept_stat, moving the accept_stat value in the response buffer
down by two words.
Instead, let's have the ->accept() methods each set the proper
final location of the accept_stat to avoid having to move
things.

Hi,

I bisected to this (4bcf0343e8)

Assuming you did the bisect on the NFS server's kernel?

as it breaks nfs3-only servers in 6.3. I.e. /etc/nfs.conf containing:
[nfsd]
vers4=no

Note: Changing the settings in /etc/nfs.conf had no effect
on my server, so I effected the change by stopping the
server and poking values into /proc/fs/nfsd/versions by
hand.

Steve?

The client sees:
 mount("10.0.2.15:/tmp", "/mnt", "nfs", 0, "vers=4.2,addr=10.0.2.15,clientad"...) = -1 EIO (Input/output error)
 write(2, "mount.nfs: mount system call fai"..., 45
 mount.nfs: mount system call failed for /mnt

And the kernel says:
 nfs4_discover_server_trunking unhandled error -5. Exiting with error EIO

I reported in downstream as:
https://bugzilla.suse.com/show_bug.cgi?id=1210995

It cannot be reverted cleanly on the top of 6.3.

Any ideas?

I can reproduce a similar problem. Network capture shows
that the server is responding with NFS4ERR_NOENT to the
EXCHANGE_ID operation, and the client kernel log says:

 nfs4_discover_server_trunking unhandled error -121. Exiting with error EIO

That's not the failure mode I expected given the commit
you bisected to, so it might not be the same problem you've
hit. I'll troubleshoot this and send a fix for testing.

Thanks.

quoted

Signed-off-by: Chuck Lever <redacted>
---
 include/linux/sunrpc/svc.h        |   19 +++++++++++++++++++
 net/sunrpc/auth_gss/svcauth_gss.c |   21 ++++++++++-----------
 net/sunrpc/svc.c                  |    2 --
 net/sunrpc/svcauth_unix.c         |    6 ++++++
 4 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index f40a90ca5de6..392d2d2620fa 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h

@@ -544,4 +544,23 @@ static inline void svcxdr_set_auth_slack(struct svc_rqst *rqstp, int slack)
  WARN_ON(xdr->p > xdr->end);
 }
 +/**
+ * svcxdr_set_accept_stat - Reserve space for the accept_stat field
+ * @rqstp: RPC transaction context
+ *
+ * Return values:
+ *   %true: Success
+ *   %false: No response buffer space was available
+ */
+static inline bool svcxdr_set_accept_stat(struct svc_rqst *rqstp)
+{
+ struct xdr_stream *xdr = &rqstp->rq_res_stream;
+
+ rqstp->rq_accept_statp = xdr_reserve_space(xdr, XDR_UNIT);
+ if (unlikely(!rqstp->rq_accept_statp))
+ return false;
+ *rqstp->rq_accept_statp = rpc_success;
+ return true;
+}
+
 #endif /* SUNRPC_SVC_H */

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 560fb8a2803d..333873abb7d9 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c

@@ -1220,7 +1220,7 @@ svcauth_gss_legacy_init(struct svc_rqst *rqstp,
  if (!svcauth_gss_proc_init_verf(sn->rsc_cache, rqstp, &rsip->out_handle,
  &rsip->major_status, GSS_SEQ_WIN))
  goto out;
- if (xdr_stream_encode_u32(&rqstp->rq_res_stream, RPC_SUCCESS) < 0)
+ if (!svcxdr_set_accept_stat(rqstp))
  goto out;
  if (!svcxdr_encode_gss_init_res(&rqstp->rq_res_stream, &rsip->out_handle,
  &rsip->out_token, rsip->major_status,

@@ -1348,7 +1348,7 @@ static int svcauth_gss_proxy_init(struct svc_rqst *rqstp,
  if (!svcauth_gss_proc_init_verf(sn->rsc_cache, rqstp, &cli_handle,
  &ud.major_status, GSS_SEQ_WIN))
  goto out;
- if (xdr_stream_encode_u32(&rqstp->rq_res_stream, RPC_SUCCESS) < 0)
+ if (!svcxdr_set_accept_stat(rqstp))
  goto out;
  if (!svcxdr_encode_gss_init_res(&rqstp->rq_res_stream, &cli_handle,
  &ud.out_token, ud.major_status,

@@ -1640,16 +1640,18 @@ svcauth_gss_accept(struct svc_rqst *rqstp)
  case RPC_GSS_PROC_DESTROY:
  if (!svcauth_gss_encode_verf(rqstp, rsci->mechctx, gc->gc_seq))
  goto auth_err;
+ if (!svcxdr_set_accept_stat(rqstp))
+ goto auth_err;
  /* Delete the entry from the cache_list and call cache_put */
  sunrpc_cache_unhash(sn->rsc_cache, &rsci->h);
- if (xdr_stream_encode_u32(&rqstp->rq_res_stream, RPC_SUCCESS) < 0)
- goto auth_err;
  goto complete;
  case RPC_GSS_PROC_DATA:
  rqstp->rq_auth_stat = rpcsec_gsserr_ctxproblem;
  svcdata->verf_start = xdr_reserve_space(&rqstp->rq_res_stream, 0);
  if (!svcauth_gss_encode_verf(rqstp, rsci->mechctx, gc->gc_seq))
  goto auth_err;
+ if (!svcxdr_set_accept_stat(rqstp))
+ goto auth_err;
  rqstp->rq_cred = rsci->cred;
  get_group_info(rsci->cred.cr_group_info);
  rqstp->rq_auth_stat = rpc_autherr_badcred;

@@ -1706,7 +1708,6 @@ svcauth_gss_accept(struct svc_rqst *rqstp)
 static __be32 *
 svcauth_gss_prepare_to_wrap(struct svc_rqst *rqstp, struct gss_svc_data *gsd)
 {
- struct xdr_buf *resbuf = &rqstp->rq_res;
  __be32 *p;
  u32 verf_len;
 @@ -1721,13 +1722,11 @@ svcauth_gss_prepare_to_wrap(struct svc_rqst *rqstp, struct gss_svc_data *gsd)
  p += 1;
  verf_len = ntohl(*p++);
  p += XDR_QUADLEN(verf_len);
- /* move accept_stat to right place: */
- memcpy(p, p + 2, 4);
- /* Also don't wrap if the accept stat is nonzero: */
- if (*p != rpc_success) {
- resbuf->head[0].iov_len -= 2 * 4;
+
+ /* Also don't wrap if the accept_stat is nonzero: */
+ if (*rqstp->rq_accept_statp != rpc_success)
  return NULL;
- }
+
  p++;
  return p;
 }

diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 3c194e6f8f5e..c2ed8b06fadb 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c

@@ -1314,8 +1314,6 @@ svc_process_common(struct svc_rqst *rqstp)
  trace_svc_process(rqstp, progp->pg_name);
    aoffset = xdr_stream_pos(xdr);
- rqstp->rq_accept_statp = xdr_reserve_space(&rqstp->rq_res_stream, XDR_UNIT);
- *rqstp->rq_accept_statp = rpc_success;
    /* un-reserve some of the out-queue now that we have a
   * better idea of reply size

diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index b101700d155c..62dfc8cdf8c5 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c

@@ -775,6 +775,8 @@ svcauth_null_accept(struct svc_rqst *rqstp)
  if (xdr_stream_encode_opaque_auth(&rqstp->rq_res_stream,
    RPC_AUTH_NULL, NULL, 0) < 0)
  return SVC_CLOSE;
+ if (!svcxdr_set_accept_stat(rqstp))
+ return SVC_CLOSE;
    rqstp->rq_cred.cr_flavor = RPC_AUTH_NULL;
  return SVC_OK;

@@ -866,6 +868,8 @@ svcauth_tls_accept(struct svc_rqst *rqstp)
    RPC_AUTH_NULL, NULL, 0) < 0)
  return SVC_CLOSE;
  }
+ if (!svcxdr_set_accept_stat(rqstp))
+ return SVC_CLOSE;
    rqstp->rq_cred.cr_flavor = RPC_AUTH_TLS;
  return SVC_OK;

@@ -960,6 +964,8 @@ svcauth_unix_accept(struct svc_rqst *rqstp)
  if (xdr_stream_encode_opaque_auth(&rqstp->rq_res_stream,
    RPC_AUTH_NULL, NULL, 0) < 0)
  return SVC_CLOSE;
+ if (!svcxdr_set_accept_stat(rqstp))
+ return SVC_CLOSE;
    rqstp->rq_cred.cr_flavor = RPC_AUTH_UNIX;
  return SVC_OK;

-- 
js
suse labs

--
Chuck Lever