fs: fix incorrect lflags value in the move_mount syscall

[ Upstream commit 593d9e4 ]

The lflags value used to look up from_path was overwritten by the one used
to look up to_path.

In other words, from_path was looked up with the wrong lflags value. Fix it.

Fixes: f9fde81 ("fs: support getname_maybe_null() in move_mount()")
Signed-off-by: Yuntao Wang <yuntao.wang@linux.dev>
Link: https://lore.kernel.org/20250811052426.129188-1-yuntao.wang@linux.dev
[Christian Brauner <brauner@kernel.org>: massage patch]
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: ytcoode

fs/namespace.c

@@ -4657,20 +4657,10 @@ SYSCALL_DEFINE5(move_mount,
 	if (flags & MOVE_MOUNT_SET_GROUP)	mflags |= MNT_TREE_PROPAGATION;
 	if (flags & MOVE_MOUNT_BENEATH)		mflags |= MNT_TREE_BENEATH;
 
-	lflags = 0;
-	if (flags & MOVE_MOUNT_F_SYMLINKS)	lflags |= LOOKUP_FOLLOW;
-	if (flags & MOVE_MOUNT_F_AUTOMOUNTS)	lflags |= LOOKUP_AUTOMOUNT;
 	uflags = 0;
-	if (flags & MOVE_MOUNT_F_EMPTY_PATH)	uflags = AT_EMPTY_PATH;
-	from_name = getname_maybe_null(from_pathname, uflags);
-	if (IS_ERR(from_name))
-		return PTR_ERR(from_name);
+	if (flags & MOVE_MOUNT_T_EMPTY_PATH)
+		uflags = AT_EMPTY_PATH;
 
-	lflags = 0;
-	if (flags & MOVE_MOUNT_T_SYMLINKS)	lflags |= LOOKUP_FOLLOW;
-	if (flags & MOVE_MOUNT_T_AUTOMOUNTS)	lflags |= LOOKUP_AUTOMOUNT;
-	uflags = 0;
-	if (flags & MOVE_MOUNT_T_EMPTY_PATH)	uflags = AT_EMPTY_PATH;
 	to_name = getname_maybe_null(to_pathname, uflags);
 	if (IS_ERR(to_name))
 		return PTR_ERR(to_name);
@@ -4683,11 +4673,24 @@ SYSCALL_DEFINE5(move_mount,
 		to_path = fd_file(f_to)->f_path;
 		path_get(&to_path);
 	} else {
+		lflags = 0;
+		if (flags & MOVE_MOUNT_T_SYMLINKS)
+			lflags |= LOOKUP_FOLLOW;
+		if (flags & MOVE_MOUNT_T_AUTOMOUNTS)
+			lflags |= LOOKUP_AUTOMOUNT;
 		ret = filename_lookup(to_dfd, to_name, lflags, &to_path, NULL);
 		if (ret)
 			return ret;
 	}
 
+	uflags = 0;
+	if (flags & MOVE_MOUNT_F_EMPTY_PATH)
+		uflags = AT_EMPTY_PATH;
+
+	from_name = getname_maybe_null(from_pathname, uflags);
+	if (IS_ERR(from_name))
+		return PTR_ERR(from_name);
+
 	if (!from_name && from_dfd >= 0) {
 		CLASS(fd_raw, f_from)(from_dfd);
 		if (fd_empty(f_from))
@@ -4696,6 +4699,11 @@ SYSCALL_DEFINE5(move_mount,
 		return vfs_move_mount(&fd_file(f_from)->f_path, &to_path, mflags);
 	}
 
+	lflags = 0;
+	if (flags & MOVE_MOUNT_F_SYMLINKS)
+		lflags |= LOOKUP_FOLLOW;
+	if (flags & MOVE_MOUNT_F_AUTOMOUNTS)
+		lflags |= LOOKUP_AUTOMOUNT;
 	ret = filename_lookup(from_dfd, from_name, lflags, &from_path, NULL);
 	if (ret)
 		return ret;