1 files changed, 69 insertions, 57 deletions

diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index ceb60c78bfc0..8d51101771fc 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1608,16 +1608,13 @@ out_security_failure:
 }
 
 /*
- * Select a security flavor for this mount.  The selected flavor
- * is planted in args->auth_flavors[0].
- *
- * Returns 0 on success, -EACCES on failure.
+ * Ensure that the specified authtype in args->auth_flavors[0] is supported by
+ * the server. Returns 0 if it's ok, and -EACCES if not.
  */
-static int nfs_select_flavor(struct nfs_parsed_mount_data *args,
-                              struct nfs_mount_request *request)
+static int nfs_verify_authflavor(struct nfs_parsed_mount_data *args,
+                        rpc_authflavor_t *server_authlist, unsigned int count)
 {
-        unsigned int i, count = *(request->auth_flav_len);
-        rpc_authflavor_t flavor;
+        unsigned int i;
 
         /*
          * If the sec= mount option is used, the specified flavor or AUTH_NULL
@@ -1627,60 +1624,19 @@ static int nfs_select_flavor(struct nfs_parsed_mount_data *args,
          * means that the server will ignore the rpc creds, so any flavor
          * can be used.
          */
-        if (args->auth_flavors[0] != RPC_AUTH_MAXFLAVOR) {
-                for (i = 0; i < count; i++) {
-                        if (args->auth_flavors[0] == request->auth_flavs[i] ||
-                            request->auth_flavs[i] == RPC_AUTH_NULL)
-                                goto out;
-                }
-                dfprintk(MOUNT, "NFS: auth flavor %d not supported by server\n",
-                        args->auth_flavors[0]);
-                goto out_err;
-        }
-
-        /*
-         * RFC 2623, section 2.7 suggests we SHOULD prefer the
-         * flavor listed first.  However, some servers list
-         * AUTH_NULL first.  Avoid ever choosing AUTH_NULL.
-         */
         for (i = 0; i < count; i++) {
-                struct rpcsec_gss_info info;
-
-                flavor = request->auth_flavs[i];
-                switch (flavor) {
-                case RPC_AUTH_UNIX:
-                        goto out_set;
-                case RPC_AUTH_NULL:
-                        continue;
-                default:
-                        if (rpcauth_get_gssinfo(flavor, &info) == 0)
-                                goto out_set;
-                }
+                if (args->auth_flavors[0] == server_authlist[i] ||
+                    server_authlist[i] == RPC_AUTH_NULL)
+                        goto out;
         }
 
-        /*
-         * As a last chance, see if the server list contains AUTH_NULL -
-         * if it does, use the default flavor.
-         */
-        for (i = 0; i < count; i++) {
-                if (request->auth_flavs[i] == RPC_AUTH_NULL)
-                        goto out_default;
-        }
-
-        dfprintk(MOUNT, "NFS: no auth flavors in common with server\n");
-        goto out_err;
+        dfprintk(MOUNT, "NFS: auth flavor %u not supported by server\n",
+                args->auth_flavors[0]);
+        return -EACCES;
 
-out_default:
-        /* use default if flavor not already set */
-        flavor = (args->auth_flavors[0] == RPC_AUTH_MAXFLAVOR) ?
-                RPC_AUTH_UNIX : args->auth_flavors[0];
-out_set:
-        args->auth_flavors[0] = flavor;
 out:
-        dfprintk(MOUNT, "NFS: using auth flavor %d\n", args->auth_flavors[0]);
+        dfprintk(MOUNT, "NFS: using auth flavor %u\n", args->auth_flavors[0]);
         return 0;
-out_err:
-        return -EACCES;
 }
 
 /*
@@ -1743,13 +1699,17 @@ static int nfs_request_mount(struct nfs_parsed_mount_data *args,
                 return status;
         }
 
-        return nfs_select_flavor(args, &request);
+        return 0;
 }
 
 static struct nfs_server *nfs_try_mount_request(struct nfs_mount_info *mount_info,
                                         struct nfs_subversion *nfs_mod)
 {
         int status;
+        unsigned int i;
+        bool tried_auth_unix = false;
+        bool auth_null_in_list = false;
+        struct nfs_server *server = ERR_PTR(-EACCES);
         struct nfs_parsed_mount_data *args = mount_info->parsed;
         rpc_authflavor_t authlist[NFS_MAX_SECFLAVORS];
         unsigned int authlist_len = ARRAY_SIZE(authlist);
@@ -1759,6 +1719,58 @@ static struct nfs_server *nfs_try_mount_request(struct nfs_mount_info *mount_inf
         if (status)
                 return ERR_PTR(status);
 
+        /*
+         * Was a sec= authflavor specified in the options? First, verify
+         * whether the server supports it, and then just try to use it if so.
+         */
+        if (args->auth_flavors[0] != RPC_AUTH_MAXFLAVOR) {
+                status = nfs_verify_authflavor(args, authlist, authlist_len);
+                dfprintk(MOUNT, "NFS: using auth flavor %u\n", args->auth_flavors[0]);
+                if (status)
+                        return ERR_PTR(status);
+                return nfs_mod->rpc_ops->create_server(mount_info, nfs_mod);
+        }
+
+        /*
+         * No sec= option was provided. RFC 2623, section 2.7 suggests we
+         * SHOULD prefer the flavor listed first. However, some servers list
+         * AUTH_NULL first. Avoid ever choosing AUTH_NULL.
+         */
+        for (i = 0; i < authlist_len; ++i) {
+                rpc_authflavor_t flavor;
+                struct rpcsec_gss_info info;
+
+                flavor = authlist[i];
+                switch (flavor) {
+                case RPC_AUTH_UNIX:
+                        tried_auth_unix = true;
+                        break;
+                case RPC_AUTH_NULL:
+                        auth_null_in_list = true;
+                        continue;
+                default:
+                        if (rpcauth_get_gssinfo(flavor, &info) != 0)
+                                continue;
+                        /* Fallthrough */
+                }
+                dfprintk(MOUNT, "NFS: attempting to use auth flavor %u\n", flavor);
+                args->auth_flavors[0] = flavor;
+                server = nfs_mod->rpc_ops->create_server(mount_info, nfs_mod);
+                if (!IS_ERR(server))
+                        return server;
+        }
+
+        /*
+         * Nothing we tried so far worked. At this point, give up if we've
+         * already tried AUTH_UNIX or if the server's list doesn't contain
+         * AUTH_NULL
+         */
+        if (tried_auth_unix || !auth_null_in_list)
+                return server;
+
+        /* Last chance! Try AUTH_UNIX */
+        dfprintk(MOUNT, "NFS: attempting to use auth flavor %u\n", RPC_AUTH_UNIX);
+        args->auth_flavors[0] = RPC_AUTH_UNIX;
         return nfs_mod->rpc_ops->create_server(mount_info, nfs_mod);
 }