From: Chuck Lever Date: Tue, 28 Nov 2023 22:01:30 +0000 (-0500) Subject: NFSD: Fix "start of NFS reply" pointer passed to nfsd_cache_update() X-Git-Tag: v6.1.68~334 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b597f3c85d2eaef1766310f92260cbf0e743de69;p=platform%2Fkernel%2Flinux-starfive.git NFSD: Fix "start of NFS reply" pointer passed to nfsd_cache_update() [ Upstream commit 1caf5f61dd8430ae5a0b4538afe4953ce7517cbb ] 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 Tested-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c index 6b20f28..ca2a9d0 100644 --- a/fs/nfsd/nfssvc.c +++ b/fs/nfsd/nfssvc.c @@ -1027,6 +1027,7 @@ out: int nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp) { const struct svc_procedure *proc = rqstp->rq_procinfo; + __be32 *nfs_reply; /* * Give the xdr decoder a chance to change this if it wants @@ -1053,6 +1054,7 @@ int nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp) */ svcxdr_init_encode(rqstp); + nfs_reply = xdr_inline_decode(&rqstp->rq_res_stream, 0); *statp = proc->pc_func(rqstp); if (*statp == rpc_drop_reply || test_bit(RQ_DROPME, &rqstp->rq_flags)) goto out_update_drop; @@ -1060,7 +1062,7 @@ int nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp) if (!proc->pc_encode(rqstp, &rqstp->rq_res_stream)) goto out_encode_err; - nfsd_cache_update(rqstp, rqstp->rq_cachetype, statp + 1); + nfsd_cache_update(rqstp, rqstp->rq_cachetype, nfs_reply); out_cached_reply: return 1;