From 0e2a07d71a6a26ac0c5719ace600a2cb6a8790dd Mon Sep 17 00:00:00 2001
From: Jakob Borg <jakob@kastelo.net>
Date: Tue, 28 Apr 2020 09:58:31 +0200
Subject: [PATCH] lib/fs: Avoid dirty offset read in fakefs (fixes #6584)

---
 lib/fs/fakefs.go | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/fs/fakefs.go b/lib/fs/fakefs.go
index 8a102bba7..df82edaae 100644
--- a/lib/fs/fakefs.go
+++ b/lib/fs/fakefs.go
@@ -754,7 +754,10 @@ func (f *fakeFile) Seek(offset int64, whence int) (int64, error) {
 }
 
 func (f *fakeFile) Write(p []byte) (int, error) {
-	return f.WriteAt(p, f.offset)
+	f.mut.Lock()
+	offs := f.offset
+	f.mut.Unlock()
+	return f.WriteAt(p, offs)
 }
 
 func (f *fakeFile) WriteAt(p []byte, off int64) (int, error) {