nfsd: refine and rename NFSD_MAY_LOCK

NFSD_MAY_LOCK means a few different things.
- it means that GSS is not required.
- it means that with NFSEXP_NOAUTHNLM, authentication is not required
- it means that OWNER_OVERRIDE is allowed.

None of these are specific to locking, they are specific to the NLM
protocol.
So:
 - rename to NFSD_MAY_NLM
 - set NFSD_MAY_OWNER_OVERRIDE and NFSD_MAY_BYPASS_GSS in nlm_fopen()
   so that NFSD_MAY_NLM doesn't need to imply these.
 - move the test on NFSEXP_NOAUTHNLM out of nfsd_permission() and
   into fh_verify where other special-case tests on the MAY flags
   happen.  nfsd_permission() can be called from other places than
   fh_verify(), but none of these will have NFSD_MAY_NLM.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/lockd.c

@@ -38,11 +38,20 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
 	memcpy(&fh.fh_handle.fh_raw, f->data, f->size);
 	fh.fh_export = NULL;
 
+	/*
+	 * Allow BYPASS_GSS as some client implementations use AUTH_SYS
+	 * for NLM even when GSS is used for NFS.
+	 * Allow OWNER_OVERRIDE as permission might have been changed
+	 * after the file was opened.
+	 * Pass MAY_NLM so that authentication can be completely bypassed
+	 * if NFSEXP_NOAUTHNLM is set.  Some older clients use AUTH_NULL
+	 * for NLM requests.
+	 */
 	access = (mode == O_WRONLY) ? NFSD_MAY_WRITE : NFSD_MAY_READ;
-	access |= NFSD_MAY_LOCK;
+	access |= NFSD_MAY_NLM | NFSD_MAY_OWNER_OVERRIDE | NFSD_MAY_BYPASS_GSS;
 	nfserr = nfsd_open(rqstp, &fh, S_IFREG, access, filp);
 	fh_put(&fh);
- 	/* We return nlm error codes as nlm doesn't know
+	/* We return nlm error codes as nlm doesn't know
 	 * about nfsd, but nfsd does know about nlm..
 	 */
 	switch (nfserr) {

fs/nfsd/nfsfh.c

@@ -363,13 +363,10 @@ __fh_verify(struct svc_rqst *rqstp,
 	if (error)
 		goto out;
 
-	/*
+	if ((access & NFSD_MAY_NLM) && (exp->ex_flags & NFSEXP_NOAUTHNLM))
-	 * pseudoflavor restrictions are not enforced on NLM,
+		/* NLM is allowed to fully bypass authentication */
-	 * which clients virtually always use auth_sys for,
+		goto out;
-	 * even while using RPCSEC_GSS for NFS.
+
-	 */
-	if (access & NFSD_MAY_LOCK)
-		goto skip_pseudoflavor_check;
 	if (access & NFSD_MAY_BYPASS_GSS)
 		may_bypass_gss = true;
 	/*
@@ -385,7 +382,6 @@ __fh_verify(struct svc_rqst *rqstp,
 	if (error)
 		goto out;
 
-skip_pseudoflavor_check:
 	/* Finally, check access permissions. */
 	error = nfsd_permission(cred, exp, dentry, access);
 out:

fs/nfsd/trace.h

@@ -79,7 +79,7 @@ DEFINE_NFSD_XDR_ERR_EVENT(cant_encode);
 		{ NFSD_MAY_READ,		"READ" },		\
 		{ NFSD_MAY_SATTR,		"SATTR" },		\
 		{ NFSD_MAY_TRUNC,		"TRUNC" },		\
-		{ NFSD_MAY_LOCK,		"LOCK" },		\
+		{ NFSD_MAY_NLM,			"NLM" },		\
 		{ NFSD_MAY_OWNER_OVERRIDE,	"OWNER_OVERRIDE" },	\
 		{ NFSD_MAY_LOCAL_ACCESS,	"LOCAL_ACCESS" },	\
 		{ NFSD_MAY_BYPASS_GSS_ON_ROOT,	"BYPASS_GSS_ON_ROOT" },	\

fs/nfsd/vfs.c

@@ -2506,7 +2506,7 @@ nfsd_permission(struct svc_cred *cred, struct svc_export *exp,
 		(acc & NFSD_MAY_EXEC)?	" exec"  : "",
 		(acc & NFSD_MAY_SATTR)?	" sattr" : "",
 		(acc & NFSD_MAY_TRUNC)?	" trunc" : "",
-		(acc & NFSD_MAY_LOCK)?	" lock"  : "",
+		(acc & NFSD_MAY_NLM)?	" nlm"  : "",
 		(acc & NFSD_MAY_OWNER_OVERRIDE)? " owneroverride" : "",
 		inode->i_mode,
 		IS_IMMUTABLE(inode)?	" immut" : "",
@@ -2531,16 +2531,6 @@ nfsd_permission(struct svc_cred *cred, struct svc_export *exp,
 	if ((acc & NFSD_MAY_TRUNC) && IS_APPEND(inode))
 		return nfserr_perm;
 
-	if (acc & NFSD_MAY_LOCK) {
-		/* If we cannot rely on authentication in NLM requests,
-		 * just allow locks, otherwise require read permission, or
-		 * ownership
-		 */
-		if (exp->ex_flags & NFSEXP_NOAUTHNLM)
-			return 0;
-		else
-			acc = NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE;
-	}
 	/*
 	 * The file owner always gets access permission for accesses that
 	 * would normally be checked at open time. This is to make

fs/nfsd/vfs.h

@@ -20,7 +20,7 @@
 #define NFSD_MAY_READ			0x004 /* == MAY_READ */
 #define NFSD_MAY_SATTR			0x008
 #define NFSD_MAY_TRUNC			0x010
-#define NFSD_MAY_LOCK			0x020
+#define NFSD_MAY_NLM			0x020 /* request is from lockd */
 #define NFSD_MAY_MASK			0x03f
 
 /* extra hints to permission and open routines: */