NFS: use secinfo when crossing mountpoints

A submount may use different security than the parent
mount does.  We should figure out what sec flavor the
submount uses at mount time.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 110 insertions, 3 deletions

diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index b02720864de..ad92bf731ff 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -15,6 +15,7 @@
 #include <linux/string.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/vfs.h>
+#include <linux/sunrpc/gss_api.h>
 #include "internal.h"
 
 #define NFSDBG_FACILITY		NFSDBG_VFS
@@ -27,7 +28,8 @@ int nfs_mountpoint_expiry_timeout = 500 * HZ;
 
 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
 					struct nfs_fh *fh,
-					struct nfs_fattr *fattr);
+					struct nfs_fattr *fattr,
+					rpc_authflavor_t authflavor);
 
 /*
  * nfs_path - reconstruct the path given an arbitrary dentry
@@ -116,6 +118,100 @@ Elong:
 	return ERR_PTR(-ENAMETOOLONG);
 }
 
+#ifdef CONFIG_NFS_V4
+static rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors, struct inode *inode)
+{
+	struct gss_api_mech *mech;
+	struct xdr_netobj oid;
+	int i;
+	rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;
+
+	for (i = 0; i < flavors->num_flavors; i++) {
+		struct nfs4_secinfo_flavor *flavor;
+		flavor = &flavors->flavors[i];
+
+		if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
+			pseudoflavor = flavor->flavor;
+			break;
+		} else if (flavor->flavor == RPC_AUTH_GSS) {
+			oid.len  = flavor->gss.sec_oid4.len;
+			oid.data = flavor->gss.sec_oid4.data;
+			mech = gss_mech_get_by_OID(&oid);
+			if (!mech)
+				continue;
+			pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
+			gss_mech_put(mech);
+			break;
+		}
+	}
+
+	return pseudoflavor;
+}
+
+static rpc_authflavor_t nfs_negotiate_security(const struct dentry *parent, const struct dentry *dentry)
+{
+	int status = 0;
+	struct page *page;
+	struct nfs4_secinfo_flavors *flavors;
+	int (*secinfo)(struct inode *, const struct qstr *, struct nfs4_secinfo_flavors *);
+	rpc_authflavor_t flavor = RPC_AUTH_UNIX;
+
+	secinfo = NFS_PROTO(parent->d_inode)->secinfo;
+	if (secinfo != NULL) {
+		page = alloc_page(GFP_KERNEL);
+		if (!page) {
+			status = -ENOMEM;
+			goto out;
+		}
+		flavors = page_address(page);
+		status = secinfo(parent->d_inode, &dentry->d_name, flavors);
+		flavor = nfs_find_best_sec(flavors, dentry->d_inode);
+		put_page(page);
+	}
+
+	return flavor;
+
+out:
+	status = -ENOMEM;
+	return status;
+}
+
+static rpc_authflavor_t nfs_lookup_with_sec(struct nfs_server *server, struct dentry *parent,
+				     struct dentry *dentry, struct path *path,
+				     struct nfs_fh *fh, struct nfs_fattr *fattr)
+{
+	rpc_authflavor_t flavor;
+	struct rpc_clnt *clone;
+	struct rpc_auth *auth;
+	int err;
+
+	flavor = nfs_negotiate_security(parent, path->dentry);
+	if (flavor < 0)
+		goto out;
+	clone  = rpc_clone_client(server->client);
+	auth   = rpcauth_create(flavor, clone);
+	if (!auth) {
+		flavor = -EIO;
+		goto out;
+	}
+	err = server->nfs_client->rpc_ops->lookup(clone, parent->d_inode,
+						  &path->dentry->d_name,
+						  fh, fattr);
+	if (err < 0)
+		flavor = err;
+out:
+	return flavor;
+}
+#else /* CONFIG_NFS_V4 */
+static inline rpc_authflavor_t nfs_lookup_with_sec(struct nfs_server *server,
+				     struct dentry *parent, struct dentry *dentry,
+				     struct path *path, struct nfs_fh *fh,
+				     struct nfs_fattr *fattr)
+{
+	return -EPERM;
+}
+#endif /* CONFIG_NFS_V4 */
+
 /*
  * nfs_d_automount - Handle crossing a mountpoint on the server
  * @path - The mountpoint
@@ -136,6 +232,7 @@ struct vfsmount *nfs_d_automount(struct path *path)
 	struct nfs_fh *fh = NULL;
 	struct nfs_fattr *fattr = NULL;
 	int err;
+	rpc_authflavor_t flavor = 1;
 
 	dprintk("--> nfs_d_automount()\n");
 
@@ -156,6 +253,13 @@ struct vfsmount *nfs_d_automount(struct path *path)
 	err = server->nfs_client->rpc_ops->lookup(server->client, parent->d_inode,
 						  &path->dentry->d_name,
 						  fh, fattr);
+	if (err == -EPERM) {
+		flavor = nfs_lookup_with_sec(server, parent, path->dentry, path, fh, fattr);
+		if (flavor < 0)
+			err = flavor;
+		else
+			err = 0;
+	}
 	dput(parent);
 	if (err != 0) {
 		mnt = ERR_PTR(err);
@@ -165,7 +269,7 @@ struct vfsmount *nfs_d_automount(struct path *path)
 	if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
 		mnt = nfs_do_refmount(path->dentry);
 	else
-		mnt = nfs_do_submount(path->dentry, fh, fattr);
+		mnt = nfs_do_submount(path->dentry, fh, fattr, flavor);
 	if (IS_ERR(mnt))
 		goto out;
 
@@ -232,17 +336,20 @@ static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
  * @dentry - parent directory
  * @fh - filehandle for new root dentry
  * @fattr - attributes for new root inode
+ * @authflavor - security flavor to use when performing the mount
  *
  */
 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
 					struct nfs_fh *fh,
-					struct nfs_fattr *fattr)
+					struct nfs_fattr *fattr,
+					rpc_authflavor_t authflavor)
 {
 	struct nfs_clone_mount mountdata = {
 		.sb = dentry->d_sb,
 		.dentry = dentry,
 		.fh = fh,
 		.fattr = fattr,
+		.authflavor = authflavor,
 	};
 	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 	char *page = (char *) __get_free_page(GFP_USER);