[dev.fuzz] internal/fuzz: fix panic when marshaling data

The coordinator needs to marshal data that was provided
via f.Add. However, it was also attempting to marshal data
that was in testdata, which was not needed,
and was causing a panic. This change fixes this.

Fixes golang/go#48228

Change-Id: I1256c5a287b5a09d2f8cca59beb0f0fc06cc3554
Reviewed-on: https://go-review.googlesource.com/c/go/+/348381
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

diff --git a/src/cmd/go/testdata/script/test_fuzz.txt b/src/cmd/go/testdata/script/test_fuzz.txt
index d3c7b4d55fb2f1afd0223700cfd10f9ef95e522c..a25f0fba3f4f4e5130ab503b6459044ad6ec0a44 100644 (file)
--- a/src/cmd/go/testdata/script/test_fuzz.txt
+++ b/src/cmd/go/testdata/script/test_fuzz.txt
@@ -160,6 +160,21 @@ stdout ok
 ! stdout FAIL
 ! stdout 'fatal here'
 
+# Test pass with testdata and f.Add seed corpus
+go test -run FuzzPassString corpustesting/fuzz_testdata_corpus_test.go
+stdout ok
+! stdout FAIL
+
+# Fuzzing pass with testdata and f.Add seed corpus (skip running tests first)
+go test -run=None -fuzz=FuzzPassString corpustesting/fuzz_testdata_corpus_test.go -fuzztime=10x
+stdout ok
+! stdout FAIL
+
+# Fuzzing pass with testdata and f.Add seed corpus
+go test -run=FuzzPassString -fuzz=FuzzPassString corpustesting/fuzz_testdata_corpus_test.go -fuzztime=10x
+stdout ok
+! stdout FAIL
+
 # Test panic with malformed seed corpus
 ! go test -run FuzzFail corpustesting/fuzz_testdata_corpus_test.go
 ! stdout ^ok
@@ -413,6 +428,11 @@ func FuzzPass(f *testing.F) {
     fuzzFn(f)
 }
 
+func FuzzPassString(f *testing.F) {
+    f.Add("some seed corpus")
+    f.Fuzz(func(*testing.T, string) {})
+}
+
 func FuzzPanic(f *testing.F) {
     f.Fuzz(func(t *testing.T, b []byte) {})
 }
@@ -431,6 +451,9 @@ go test fuzz v1
 -- corpustesting/testdata/corpus/FuzzPass/1 --
 go test fuzz v1
 []byte("00000")
+-- corpustesting/testdata/corpus/FuzzPassString/1 --
+go test fuzz v1
+string("hello")
 -- corpustesting/testdata/corpus/FuzzPanic/1 --
 malformed
 -- corpustesting/testdata/corpus/FuzzInNestedDir/anotherdir/1 --

diff --git a/src/internal/fuzz/fuzz.go b/src/internal/fuzz/fuzz.go
index 5b940e4929b81e838e7293220a2d75e28c497f86..f36569b4cc595d47d1ec72b57501f43668e3ccad 100644 (file)
--- a/src/internal/fuzz/fuzz.go
+++ b/src/internal/fuzz/fuzz.go
@@ -576,9 +576,9 @@ type coordinator struct {
 }
 
 func newCoordinator(opts CoordinateFuzzingOpts) (*coordinator, error) {
-       // Make sure all of the seed corpus has marshalled data.
+       // Make sure all of the seed corpus given by f.Add has marshalled data.
        for i := range opts.Seed {
-               if opts.Seed[i].Data == nil {
+               if opts.Seed[i].Data == nil && opts.Seed[i].Values != nil {
                        opts.Seed[i].Data = marshalCorpusFile(opts.Seed[i].Values...)
                }
        }