lib/model: Check for symlinks before deleting during pull (fixes #6090) (#6100)

lib/model/folder_sendrecv.go

@@ -847,10 +847,17 @@ func (f *sendReceiveFolder) deleteFileWithCurrent(file, cur protocol.FileInfo, h
 
 	if !hasCur {
 		// We should never try to pull a deletion for a file we don't have in the DB.
-		l.Debugln(f, "not deleting file we don't have", file.Name)
+		l.Debugln(f, "not deleting file we don't have, but update db", file.Name)
 		dbUpdateChan <- dbUpdateJob{file, dbUpdateDeleteFile}
 		return
 	}
+
+	if err = osutil.TraversesSymlink(f.fs, filepath.Dir(file.Name)); err != nil {
+		l.Debugln(f, "not deleting file behind symlink on disk, but update db", file.Name)
+		dbUpdateChan <- dbUpdateJob{file, dbUpdateDeleteFile}
+		return
+	}
+
 	if err = f.checkToBeDeleted(cur, scanChan); err != nil {
 		return
 	}
@@ -1839,6 +1846,10 @@ func (f *sendReceiveFolder) deleteItemOnDisk(item protocol.FileInfo, scanChan ch
 // deleteDirOnDisk attempts to delete a directory. It checks for files/dirs inside
 // the directory and removes them if possible or returns an error if it fails
 func (f *sendReceiveFolder) deleteDirOnDisk(dir string, scanChan chan<- string) error {
+	if err := osutil.TraversesSymlink(f.fs, filepath.Dir(dir)); err != nil {
+		return err
+	}
+
 	files, _ := f.fs.DirNames(dir)
 
 	toBeDeleted := make([]string, 0, len(files))

lib/model/folder_sendrecv_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/syncthing/syncthing/lib/events"
 	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/ignore"
+	"github.com/syncthing/syncthing/lib/osutil"
 	"github.com/syncthing/syncthing/lib/protocol"
 	"github.com/syncthing/syncthing/lib/scanner"
 	"github.com/syncthing/syncthing/lib/sync"
@@ -124,7 +125,7 @@ func setupSendReceiveFolder(files ...protocol.FileInfo) (*model, *sendReceiveFol
 func cleanupSRFolder(f *sendReceiveFolder, m *model) {
 	m.evLogger.Stop()
 	os.Remove(m.cfg.ConfigPath())
-	os.Remove(f.Filesystem().URI())
+	os.RemoveAll(f.Filesystem().URI())
 }
 
 // Layout of the files: (indexes from the above array)
@@ -907,6 +908,58 @@ func TestSRConflictReplaceFileByLink(t *testing.T) {
 	}
 }
 
+// TestDeleteBehindSymlink checks that we don't delete or schedule a scan
+// when trying to delete a file behind a symlink.
+func TestDeleteBehindSymlink(t *testing.T) {
+	m, f := setupSendReceiveFolder()
+	defer cleanupSRFolder(f, m)
+	ffs := f.Filesystem()
+
+	destDir := createTmpDir()
+	defer os.RemoveAll(destDir)
+	destFs := fs.NewFilesystem(fs.FilesystemTypeBasic, destDir)
+
+	link := "link"
+	file := filepath.Join(link, "file")
+
+	must(t, ffs.MkdirAll(link, 0755))
+	fi := createFile(t, file, ffs)
+	f.updateLocalsFromScanning([]protocol.FileInfo{fi})
+	must(t, osutil.RenameOrCopy(ffs, destFs, file, "file"))
+	must(t, ffs.RemoveAll(link))
+
+	if err := osutil.DebugSymlinkForTestsOnly(destFs.URI(), filepath.Join(ffs.URI(), link)); err != nil {
+		if runtime.GOOS == "windows" {
+			// Probably we require permissions we don't have.
+			t.Skip("Need admin permissions or developer mode to run symlink test on Windows: " + err.Error())
+		} else {
+			t.Fatal(err)
+		}
+	}
+
+	fi.Deleted = true
+	fi.Version = fi.Version.Update(device1.Short())
+	scanChan := make(chan string, 1)
+	dbUpdateChan := make(chan dbUpdateJob, 1)
+	f.deleteFile(fi, dbUpdateChan, scanChan)
+	select {
+	case f := <-scanChan:
+		t.Fatalf("Received %v on scanChan", f)
+	case u := <-dbUpdateChan:
+		if u.jobType != dbUpdateDeleteFile {
+			t.Errorf("Expected jobType %v, got %v", dbUpdateDeleteFile, u.jobType)
+		}
+		if u.file.Name != fi.Name {
+			t.Errorf("Expected update for %v, got %v", fi.Name, u.file.Name)
+		}
+	default:
+		t.Fatalf("No db update received")
+	}
+	if _, err := destFs.Stat("file"); err != nil {
+		t.Errorf("Expected no error when stating file behind symlink, got %v", err)
+	}
+}
+
 func cleanupSharedPullerState(s *sharedPullerState) {
 	s.mut.Lock()
 	defer s.mut.Unlock()