mfs: take the read/write lock *before* extracting the node.

Otherwise, it could be exchanged out from under us! fixes #4514 License: MIT Signed-off-by: Steven Allen <[email protected]>
ipfs · Dec 21, 2017 · e68ef05 · e68ef05
1 parent 9beaa38
commit e68ef05
Showing 1 changed file with 18 additions and 9 deletions.
diff --git a/mfs/file.go b/mfs/file.go
@@ -42,7 +42,24 @@ func NewFile(name string, node node.Node, parent childCloser, dserv dag.DAGServi
 	return fi, nil
 }
 
-func (fi *File) Open(flags Flags) (FileDescriptor, error) {
+func (fi *File) Open(flags Flags) (_ FileDescriptor, _retErr error) {
+	if flags.Write {
+		fi.desclock.Lock()
+		defer func() {
+			if _retErr != nil {
+				fi.desclock.Unlock()
+			}
+		}()
+	} else if flags.Read {
+		fi.desclock.RLock()
+		defer func() {
+			if _retErr != nil {
+				fi.desclock.Unlock()
+			}
+		}()
+	} else {
+		return nil, fmt.Errorf("file opened for neither reading nor writing")
+	}
 	fi.nodelk.Lock()
 	node := fi.node
 	fi.nodelk.Unlock()
@@ -66,14 +83,6 @@ func (fi *File) Open(flags Flags) (FileDescriptor, error) {
 		// Ok as well.
 	}
 
-	if flags.Write {
-		fi.desclock.Lock()
-	} else if flags.Read {
-		fi.desclock.RLock()
-	} else {
-		return nil, fmt.Errorf("file opened for neither reading nor writing")
-	}
-
 	dmod, err := mod.NewDagModifier(context.TODO(), node, fi.dserv, chunk.DefaultSplitter)
 	if err != nil {
 		return nil, err