From 55bea6e7a64b1134dc5cecdd4a63961cb3b720c4 Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Fri, 14 May 2021 22:14:05 +0200
Subject: [PATCH] filter: Fix crash for '**' pattern

---
 changelog/unreleased/issue-3380 | 7 +++++++
 internal/filter/filter.go       | 5 +++++
 internal/filter/filter_test.go  | 1 +
 3 files changed, 13 insertions(+)
 create mode 100644 changelog/unreleased/issue-3380

diff --git a/changelog/unreleased/issue-3380 b/changelog/unreleased/issue-3380
new file mode 100644
index 000000000..bf18cda48
--- /dev/null
+++ b/changelog/unreleased/issue-3380
@@ -0,0 +1,7 @@
+Bugfix: Fix crash of `backup --exclude='**'`
+
+The exclude filter '**', which excludes all files, caused restic to crash. This
+has been fixed.
+
+https://github.com/restic/restic/issues/3380
+https://github.com/restic/restic/pull/3393
diff --git a/internal/filter/filter.go b/internal/filter/filter.go
index 1f6f04133..84aa82784 100644
--- a/internal/filter/filter.go
+++ b/internal/filter/filter.go
@@ -166,6 +166,11 @@ func match(patterns Pattern, strs []string) (matched bool, err error) {
 		return true, nil
 	}
 
+	// an empty pattern never matches a non-empty path
+	if len(patterns) == 0 {
+		return false, nil
+	}
+
 	if len(patterns) <= len(strs) {
 		minOffset := 0
 		maxOffset := len(strs) - len(patterns)
diff --git a/internal/filter/filter_test.go b/internal/filter/filter_test.go
index ee7f05a32..30cee40db 100644
--- a/internal/filter/filter_test.go
+++ b/internal/filter/filter_test.go
@@ -23,6 +23,7 @@ var matchTests = []struct {
 	{"*.go", "/foo/bar/test.go", true},
 	{"*.c", "/foo/bar/test.go", false},
 	{"*", "/foo/bar/test.go", true},
+	{"**", "/foo/bar/test.go", true},
 	{"foo*", "/foo/bar/test.go", true},
 	{"bar*", "/foo/bar/test.go", true},
 	{"/bar*", "/foo/bar/test.go", false},