[PATCH v5 02/18] nfsd: move check_nfsd_access() call into nfsd_cross_mnt()

From: NeilBrown <neil-+NVA1uvv1dVBDLzU/[email protected]>

Whenever we cross a mount point, we need to check_nfsd_access() for v4.
So move the call into nfsd_cross_mnt() in the place where we actually do
cross.  This avoids the possibility of calling nfsd_cross_mnt() without
the required check_nfsd_access().

Also remove the last arg from check_nfsd_access(), which is always false.

nfsd_cross_mnt() now returns an nfserr rather than an errno.

Signed-off-by: NeilBrown <neil-+NVA1uvv1dVBDLzU/[email protected]>
---
 fs/nfsd/export.c   |  6 ++----
 fs/nfsd/export.h   |  3 +--
 fs/nfsd/nfs4proc.c |  2 +-
 fs/nfsd/nfs4xdr.c  |  9 +-------
 fs/nfsd/vfs.c      | 54 +++++++++++++++++++++++++---------------------
 fs/nfsd/vfs.h      |  4 ++--
 6 files changed, 36 insertions(+), 42 deletions(-)

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index a47c90f40422..5aefb388cc27 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -1890,21 +1890,19 @@ __be32 check_security_flavor(struct svc_export *exp, struct svc_rqst *rqstp,
  * check_nfsd_access - check if access to export is allowed.
  * @exp: svc_export that is being accessed.
  * @rqstp: svc_rqst attempting to access @exp.
- * @may_bypass_gss: reduce strictness of authorization check
  *
  * Return values:
  *   %nfs_ok if access is granted, or
  *   %nfserr_wrongsec if access is denied
  */
-__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
-			 bool may_bypass_gss)
+__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp)
 {
 	__be32 status;
 
 	status = check_xprtsec_policy(exp, rqstp);
 	if (status != nfs_ok)
 		return status;
-	return check_security_flavor(exp, rqstp, may_bypass_gss);
+	return check_security_flavor(exp, rqstp, false);
 }
 
 /*
diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
index d2b09cd76145..117fb28db1e0 100644
--- a/fs/nfsd/export.h
+++ b/fs/nfsd/export.h
@@ -104,8 +104,7 @@ int nfsexp_flags(struct svc_cred *cred, struct svc_export *exp);
 __be32 check_xprtsec_policy(struct svc_export *exp, struct svc_rqst *rqstp);
 __be32 check_security_flavor(struct svc_export *exp, struct svc_rqst *rqstp,
 			     bool may_bypass_gss);
-__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
-			 bool may_bypass_gss);
+__be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp);
 
 /*
  * Function declarations
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index bb99ab6b78b5..0317ff3f1c39 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -3328,7 +3328,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
 
 			if (current_fh->fh_export &&
 					need_wrongsec_check(rqstp))
-				op->status = check_nfsd_access(current_fh->fh_export, rqstp, false);
+				op->status = check_nfsd_access(current_fh->fh_export, rqstp);
 		}
 encode_op:
 		if (op->status == nfserr_replay_me) {
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 606ddcb085c0..04755c41d871 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -4574,8 +4574,6 @@ nfsd4_encode_entry4_fattr(struct nfsd4_readdir *cd, const char *name,
 	 * directly from the mountpoint dentry.
 	 */
 	if (nfsd_mountpoint(dentry, exp)) {
-		int err;
-
 		if (!(exp->ex_flags & NFSEXP_V4ROOT)
 				&& !attributes_need_mount(cd->rd_bmval)) {
 			ignore_crossmnt = 1;
@@ -4586,12 +4584,7 @@ nfsd4_encode_entry4_fattr(struct nfsd4_readdir *cd, const char *name,
 		 * Different "."/".." handling?  Something else?
 		 * At least, add a comment here to explain....
 		 */
-		err = nfsd_cross_mnt(cd->rd_rqstp, &dentry, &exp);
-		if (err) {
-			nfserr = nfserrno(err);
-			goto out_put;
-		}
-		nfserr = check_nfsd_access(exp, cd->rd_rqstp, false);
+		nfserr = nfsd_cross_mnt(cd->rd_rqstp, &dentry, &exp);
 		if (nfserr)
 			goto out_put;
 		crossed = true;
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 8923a9910a08..7898af35874b 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -118,15 +118,15 @@ nfserrno (int errno)
 	return nfserr_io;
 }
 
-/* 
- * Called from nfsd_lookup and encode_dirent. Check if we have crossed 
+/*
+ * Called from nfsd_lookup and encode_dirent. Check if we have crossed
  * a mount point.
- * Returns -EAGAIN or -ETIMEDOUT leaving *dpp and *expp unchanged,
+ * Returns an nfs error leaving *dpp and *expp unchanged,
  *  or nfs_ok having possibly changed *dpp and *expp
  */
-int
-nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp, 
-		        struct svc_export **expp)
+__be32
+nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
+	       struct svc_export **expp)
 {
 	struct svc_export *exp = *expp, *exp2 = NULL;
 	struct dentry *dentry = *dpp;
@@ -134,6 +134,7 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
 			    .dentry = dget(dentry)};
 	unsigned int follow_flags = 0;
 	int err = 0;
+	__be32 nfserr = nfs_ok;
 
 	if (exp->ex_flags & NFSEXP_CROSSMOUNT)
 		follow_flags = LOOKUP_AUTOMOUNT;
@@ -163,23 +164,28 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
 			err = 0;
 	} else if (nfsd_v4client(rqstp) ||
 		(exp->ex_flags & NFSEXP_CROSSMOUNT) || EX_NOHIDE(exp2)) {
-		/* successfully crossed mount point */
-		/*
-		 * This is subtle: path.dentry is *not* on path.mnt
-		 * at this point.  The only reason we are safe is that
-		 * original mnt is pinned down by exp, so we should
-		 * put path *before* putting exp
-		 */
-		*dpp = path.dentry;
-		path.dentry = dentry;
-		*expp = exp2;
-		exp2 = exp;
+		nfserr = check_nfsd_access(exp, rqstp);
+		if (nfserr == nfs_ok) {
+			/* successfully crossed mount point */
+			/*
+			 * This is subtle: path.dentry is *not* on path.mnt
+			 * at this point.  The only reason we are safe is that
+			 * original mnt is pinned down by exp, so we should
+			 * put path *before* putting exp
+			 */
+			*dpp = path.dentry;
+			path.dentry = dentry;
+			*expp = exp2;
+			exp2 = exp;
+		}
 	}
 out:
 	path_put(&path);
 	if (exp2)
 		exp_put(exp2);
-	return err;
+	if (nfserr)
+		return nfserr;
+	return nfserrno(err);
 }
 
 static void follow_to_parent(struct path *path)
@@ -277,10 +283,11 @@ nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
 		if (IS_ERR(dentry))
 			goto out_nfserr;
 		if (nfsd_mountpoint(dentry, exp)) {
-			host_err = nfsd_cross_mnt(rqstp, &dentry, &exp);
-			if (host_err) {
+			int nfserr = nfsd_cross_mnt(rqstp, &dentry, &exp);
+			if (nfserr) {
 				dput(dentry);
-				goto out_nfserr;
+				exp_put(exp);
+				return nfserr;
 			}
 		}
 	}
@@ -327,9 +334,6 @@ nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
 	err = nfsd_lookup_dentry(rqstp, fhp, name, len, &exp, &dentry);
 	if (err)
 		return err;
-	err = check_nfsd_access(exp, rqstp, false);
-	if (err)
-		goto out;
 	/*
 	 * Note: we compose the file handle now, but as the
 	 * dentry may be negative, it may need to be updated.
@@ -337,7 +341,7 @@ nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
 	err = fh_compose(resfh, exp, dentry, fhp);
 	if (!err && d_really_is_negative(dentry))
 		err = nfserr_noent;
-out:
+
 	dput(dentry);
 	exp_put(exp);
 	return err;
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index 4af2ff9e9dfe..5554878781f4 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -76,8 +76,8 @@ static inline bool nfsd_attrs_valid(struct nfsd_attrs *attrs)
 }
 
 __be32		nfserrno (int errno);
-int		nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
-		                struct svc_export **expp);
+__be32		nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
+			       struct svc_export **expp);
 __be32		nfsd_lookup(struct svc_rqst *, struct svc_fh *,
 				const char *, unsigned int, struct svc_fh *);
 __be32		 nfsd_lookup_dentry(struct svc_rqst *, struct svc_fh *,
-- 
2.50.0.107.gf914562f5916.dirty