Re: [PATCH] nfsd: do nfs4_check_fh in nfs4_check_file instead of nfs4_check_olstateid

["J. Bruce Fields" <bfields@fieldses.org>]

On Thu, Jul 30, 2015 at 11:16:41AM -0400, J. Bruce Fields wrote:
> On Thu, Jul 30, 2015 at 06:57:46AM -0400, Jeff Layton wrote:
> > Currently, preprocess_stateid_op calls nfs4_check_olstateid which
> > verifies that the open stateid corresponds to the current_fh in the
> > call by calling nfs4_check_fh.
> > 
> > If the stateid is a NFS4_DELEG_STID however, then no such check is
> > done. Move the call to nfs4_check_fh into nfs4_check_file instead
> > so that it can be done for all stateid types.
> 
> Thanks, applying for 4.2 and -stable with a note that this can screw up
> permissions checking later in nfs4_check_file.

By the way I also had to apply the following to avoid a NULL dereference
in the special-stateid case (when we'll jump to the "done:" label with
"s" still NULL).  Thanks to pynfs4.0 RD1 for catching that....

--b.

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 5cee7f2c4802..95202719a1fd 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4615,10 +4615,6 @@ nfs4_check_file(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfs4_stid *s,
 	struct file *file;
 	__be32 status;
 
-	status = nfs4_check_fh(fhp, s);
-	if (status)
-		return status;
-
 	file = nfs4_find_file(s, flags);
 	if (file) {
 		status = nfsd_permission(rqstp, fhp->fh_export, fhp->fh_dentry,
@@ -4691,6 +4687,9 @@ nfs4_preprocess_stateid_op(struct svc_rqst *rqstp,
 		status = nfserr_bad_stateid;
 		break;
 	}
+	if (status)
+		goto out;
+	status = nfs4_check_fh(fhp, s);
 
 done:
 	if (!status && filpp)