From 4d4fe83b6d43b3a334406c96662ad31167853fd7 Mon Sep 17 00:00:00 2001
From: Christian Muehlhaeuser <muesli@gmail.com>
Date: Wed, 19 Jan 2022 15:51:13 +0100
Subject: [PATCH] Repository: don't crash accessing invalid pathinfo (#443)

When fs.Stat returns an error, pathinfo may be nil. In such situations
the only safe response seems to be to return the error to the caller.

Without this fix, accessing pathinfo.IsDir() below would lead to a crash
dereferencing a nil pointer.

This crash can be reproduced by trying to initialize a Git repo with an
invalid path name.

Also see: https://github.com/muesli/gitty/issues/36
---
 repository.go      | 3 +++
 repository_test.go | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/repository.go b/repository.go
index 3b02265e9..85842a3ca 100644
--- a/repository.go
+++ b/repository.go
@@ -284,6 +284,9 @@ func dotGitToOSFilesystems(path string, detect bool) (dot, wt billy.Filesystem,
 
 		pathinfo, err := fs.Stat("/")
 		if !os.IsNotExist(err) {
+			if pathinfo == nil {
+				return nil, nil, err
+			}
 			if !pathinfo.IsDir() && detect {
 				fs = osfs.New(filepath.Dir(path))
 			}
diff --git a/repository_test.go b/repository_test.go
index 9a4ed1a31..23e0cb718 100644
--- a/repository_test.go
+++ b/repository_test.go
@@ -3005,6 +3005,11 @@ func (s *RepositorySuite) TestBrokenMultipleShallowFetch(c *C) {
 	c.Assert(err, IsNil)
 }
 
+func (s *RepositorySuite) TestDotGitToOSFilesystemsInvalidPath(c *C) {
+	_, _, err := dotGitToOSFilesystems("\000", false)
+	c.Assert(err, NotNil)
+}
+
 func BenchmarkObjects(b *testing.B) {
 	defer fixtures.Clean()