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author | Chuck Lever <chuck.lever@oracle.com> | 2023-11-10 11:28:33 -0500 |
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committer | Chuck Lever <chuck.lever@oracle.com> | 2023-11-17 15:12:55 -0500 |
commit | 1caf5f61dd8430ae5a0b4538afe4953ce7517cbb (patch) | |
tree | c0fec6f1c00cd6306c68f389cb3200e9843003ae /fs | |
parent | 49cecd8628a9855cd993792a0377559ea32d5e7c (diff) | |
download | lwn-1caf5f61dd8430ae5a0b4538afe4953ce7517cbb.tar.gz lwn-1caf5f61dd8430ae5a0b4538afe4953ce7517cbb.zip |
NFSD: Fix "start of NFS reply" pointer passed to nfsd_cache_update()
The "statp + 1" pointer that is passed to nfsd_cache_update() is
supposed to point to the start of the egress NFS Reply header. In
fact, it does point there for AUTH_SYS and RPCSEC_GSS_KRB5 requests.
But both krb5i and krb5p add fields between the RPC header's
accept_stat field and the start of the NFS Reply header. In those
cases, "statp + 1" points at the extra fields instead of the Reply.
The result is that nfsd_cache_update() caches what looks to the
client like garbage.
A connection break can occur for a number of reasons, but the most
common reason when using krb5i/p is a GSS sequence number window
underrun. When an underrun is detected, the server is obliged to
drop the RPC and the connection to force a retransmit with a fresh
GSS sequence number. The client presents the same XID, it hits in
the server's DRC, and the server returns the garbage cache entry.
The "statp + 1" argument has been used since the oldest changeset
in the kernel history repo, so it has been in nfsd_dispatch()
literally since before history began. The problem arose only when
the server-side GSS implementation was added twenty years ago.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Jeff Layton <jlayton@kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/nfsd/nfssvc.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c index d6122bb2d167..b4e4e04f9931 100644 --- a/fs/nfsd/nfssvc.c +++ b/fs/nfsd/nfssvc.c @@ -981,6 +981,7 @@ int nfsd_dispatch(struct svc_rqst *rqstp) const struct svc_procedure *proc = rqstp->rq_procinfo; __be32 *statp = rqstp->rq_accept_statp; struct nfsd_cacherep *rp; + __be32 *nfs_reply; /* * Give the xdr decoder a chance to change this if it wants @@ -1010,6 +1011,7 @@ int nfsd_dispatch(struct svc_rqst *rqstp) goto out_dropit; } + nfs_reply = xdr_inline_decode(&rqstp->rq_res_stream, 0); *statp = proc->pc_func(rqstp); if (test_bit(RQ_DROPME, &rqstp->rq_flags)) goto out_update_drop; @@ -1023,7 +1025,7 @@ int nfsd_dispatch(struct svc_rqst *rqstp) */ smp_store_release(&rqstp->rq_status_counter, rqstp->rq_status_counter + 1); - nfsd_cache_update(rqstp, rp, rqstp->rq_cachetype, statp + 1); + nfsd_cache_update(rqstp, rp, rqstp->rq_cachetype, nfs_reply); out_cached_reply: return 1; |