nfsd4: fix decoding of compounds across page boundaries

commit 247500820ebd02ad87525db5d9b199e5b66f6636 upstream.

A freebsd NFSv4.0 client was getting rare IO errors expanding a tarball.
A network trace showed the server returning BAD_XDR on the final getattr
of a getattr+write+getattr compound.  The final getattr started on a
page boundary.

I believe the Linux client ignores errors on the post-write getattr, and
that that's why we haven't seen this before.

Reported-by: Rick Macklem <rmacklem@uoguelph.ca>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 6cd86e0fe450..582321a978b0 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -162,8 +162,8 @@ static __be32 *read_buf(struct nfsd4_compoundargs *argp, u32 nbytes)
          */
         memcpy(p, argp->p, avail);
         /* step to next page */
-        argp->p = page_address(argp->pagelist[0]);
         argp->pagelist++;
+        argp->p = page_address(argp->pagelist[0]);
         if (argp->pagelen < PAGE_SIZE) {
                 argp->end = argp->p + (argp->pagelen>>2);
                 argp->pagelen = 0;