From b13e9c4e3d603955f92c1542a5e86c740f43f33e Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Sun, 27 Dec 2020 21:58:39 +0100
Subject: [PATCH] tests/fuzzers: fix false positive in bitutil fuzzer (#22076)

---
 tests/fuzzers/bitutil/compress_fuzz.go | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/tests/fuzzers/bitutil/compress_fuzz.go b/tests/fuzzers/bitutil/compress_fuzz.go
index 0b77b2dc9e..5903cf2f93 100644
--- a/tests/fuzzers/bitutil/compress_fuzz.go
+++ b/tests/fuzzers/bitutil/compress_fuzz.go
@@ -51,7 +51,19 @@ func fuzzDecode(data []byte) int {
 	if err != nil {
 		return 0
 	}
-	if comp := bitutil.CompressBytes(blob); !bytes.Equal(comp, data) {
+	// re-compress it (it's OK if the re-compressed differs from the
+	// original - the first input may not have been compressed at all)
+	comp := bitutil.CompressBytes(blob)
+	if len(comp) > len(blob) {
+		// After compression, it must be smaller or equal
+		panic("bad compression")
+	}
+	// But decompressing it once again should work
+	decomp, err := bitutil.DecompressBytes(data, 1024)
+	if err != nil {
+		panic(err)
+	}
+	if !bytes.Equal(decomp, blob) {
 		panic("content mismatch")
 	}
 	return 1