From e4132f625bd9d32269047d34868a7ab3e392ed11 Mon Sep 17 00:00:00 2001
From: JustAnotherArchivist <JustAnotherArchivist@users.noreply.github.com>
Date: Mon, 19 Jul 2021 19:48:58 +0000
Subject: [PATCH] Fix race condition crash on concurrent accesses to the same
 file

https://github.com/dutchcoders/transfer.sh/issues/380
---
 server/handlers.go | 17 ++++++-----------
 server/server.go   |  4 ++--
 2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/server/handlers.go b/server/handlers.go
index dd10e73..b9e5a69 100644
--- a/server/handlers.go
+++ b/server/handlers.go
@@ -625,23 +625,18 @@ func (metadata Metadata) remainingLimitHeaderValues() (remainingDownloads, remai
 	return remainingDownloads, remainingDays
 }
 
-func (s *Server) Lock(token, filename string) error {
+func (s *Server) Lock(token, filename string) {
 	key := path.Join(token, filename)
 
-	if _, ok := s.locks[key]; !ok {
-		s.locks[key] = &sync.Mutex{}
-	}
-
-	s.locks[key].Lock()
-
-	return nil
+	lock, _ := s.locks.LoadOrStore(key, &sync.Mutex{})
+	lock.(*sync.Mutex).Lock()
 }
 
-func (s *Server) Unlock(token, filename string) error {
+func (s *Server) Unlock(token, filename string) {
 	key := path.Join(token, filename)
-	s.locks[key].Unlock()
 
-	return nil
+	lock, _ := s.locks.LoadOrStore(key, &sync.Mutex{})
+	lock.(*sync.Mutex).Unlock()
 }
 
 func (s *Server) CheckMetadata(token, filename string, increaseDownload bool) (Metadata, error) {
diff --git a/server/server.go b/server/server.go
index ed36853..b3c24e2 100644
--- a/server/server.go
+++ b/server/server.go
@@ -282,7 +282,7 @@ type Server struct {
 
 	profilerEnabled bool
 
-	locks map[string]*sync.Mutex
+	locks sync.Map
 
 	maxUploadSize     int64
 	rateLimitRequests int
@@ -321,7 +321,7 @@ type Server struct {
 
 func New(options ...OptionFn) (*Server, error) {
 	s := &Server{
-		locks: map[string]*sync.Mutex{},
+		locks: sync.Map{},
 	}
 
 	for _, optionFn := range options {