pkg/repro: fix invalid options minimization

Repro can generate Sandbox="namespace"/UseTmpDir=false.
This combination is broken for two reasons:
 - on second and subsequent executions of the program,
   it fails to create syz-tmp dir
 - with Procs>1, it fails right away, because all procs
   try to create syz-tmp dir

Don't generate such combination.

2 files changed, 15 insertions, 6 deletions

diff --git a/pkg/csource/csource.go b/pkg/csource/csource.go
index e351a2e1d..163a9b065 100644
--- a/pkg/csource/csource.go
+++ b/pkg/csource/csource.go
@@ -51,11 +51,19 @@ type Options struct {
 // Invalid combinations must not be passed to Write.
 func (opts Options) Check() error {
 	if !opts.Threaded && opts.Collide {
+		// Collide requires threaded.
 		return errors.New("Collide without Threaded")
 	}
 	if !opts.Repeat && opts.Procs > 1 {
+		// This does not affect generated code.
 		return errors.New("Procs>1 without Repeat")
 	}
+	if opts.Sandbox == "namespace" && !opts.UseTmpDir {
+		// This is borken and never worked.
+		// This tries to create syz-tmp dir in cwd,
+		// which will fail if procs>1 and on second run of the program.
+		return errors.New("Sandbox=namespace without UseTmpDir")
+	}
 	return nil
 }
 
diff --git a/pkg/csource/csource_test.go b/pkg/csource/csource_test.go
index ae34a9499..e4e9e1f7f 100644
--- a/pkg/csource/csource_test.go
+++ b/pkg/csource/csource_test.go
@@ -85,12 +85,13 @@ func allOptionsPermutations() []Options {
 func TestOne(t *testing.T) {
 	rs, _ := initTest(t)
 	opts := Options{
-		Threaded: true,
-		Collide:  true,
-		Repeat:   true,
-		Procs:    2,
-		Sandbox:  "namespace",
-		Repro:    true,
+		Threaded:  true,
+		Collide:   true,
+		Repeat:    true,
+		Procs:     2,
+		Sandbox:   "namespace",
+		Repro:     true,
+		UseTmpDir: true,
 	}
 	p := prog.GenerateAllSyzProg(rs)
 	testOne(t, p, opts)