runtime: use bootstrapRand to initialize hashkey
The seed for rand is not initialized until after alginit. Before
initialization, rand returns a deterministic sequence, making hashkey
deterministic across processes.
Switch to bootstrapRand, like other early rand calls, such as
initialization of aeskeysched.
Fixes #66885.
Change-Id: I5023a9161232b49fda2ebd1d5f9338bbdd17b1fe
Reviewed-on: https://go-review.googlesource.com/c/go/+/580136
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
diff --git a/src/runtime/alg.go b/src/runtime/alg.go
index f5125d4..aadd5f1 100644
--- a/src/runtime/alg.go
+++ b/src/runtime/alg.go
@@ -391,7 +391,7 @@
return
}
for i := range hashkey {
- hashkey[i] = uintptr(rand()) | 1 // make sure these numbers are odd
+ hashkey[i] = uintptr(bootstrapRand()) | 1 // make sure these numbers are odd
}
}
diff --git a/src/runtime/map_test.go b/src/runtime/map_test.go
index 2c51236..c29fb93 100644
--- a/src/runtime/map_test.go
+++ b/src/runtime/map_test.go
@@ -8,7 +8,9 @@
"fmt"
"internal/abi"
"internal/goarch"
+ "internal/testenv"
"math"
+ "os"
"reflect"
"runtime"
"sort"
@@ -1464,3 +1466,81 @@
}
}
}
+
+func computeHash() uintptr {
+ var v struct{}
+ return runtime.MemHash(unsafe.Pointer(&v), 0, unsafe.Sizeof(v))
+}
+
+func subprocessHash(t *testing.T, env string) uintptr {
+ t.Helper()
+
+ cmd := testenv.CleanCmdEnv(testenv.Command(t, os.Args[0], "-test.run=^TestMemHashGlobalSeed$"))
+ cmd.Env = append(cmd.Env, "GO_TEST_SUBPROCESS_HASH=1")
+ if env != "" {
+ cmd.Env = append(cmd.Env, env)
+ }
+
+ out, err := cmd.Output()
+ if err != nil {
+ t.Fatalf("cmd.Output got err %v want nil", err)
+ }
+
+ s := strings.TrimSpace(string(out))
+ h, err := strconv.ParseUint(s, 10, 64)
+ if err != nil {
+ t.Fatalf("Parse output %q got err %v want nil", s, err)
+ }
+ return uintptr(h)
+}
+
+// memhash has unique per-process seeds, so hashes should differ across
+// processes.
+//
+// Regression test for https://go.dev/issue/66885.
+func TestMemHashGlobalSeed(t *testing.T) {
+ if os.Getenv("GO_TEST_SUBPROCESS_HASH") != "" {
+ fmt.Println(computeHash())
+ os.Exit(0)
+ return
+ }
+
+ testenv.MustHaveExec(t)
+
+ // aeshash and memhashFallback use separate per-process seeds, so test
+ // both.
+ t.Run("aes", func(t *testing.T) {
+ if !*runtime.UseAeshash {
+ t.Skip("No AES")
+ }
+
+ h1 := subprocessHash(t, "")
+ t.Logf("%d", h1)
+ h2 := subprocessHash(t, "")
+ t.Logf("%d", h2)
+ h3 := subprocessHash(t, "")
+ t.Logf("%d", h3)
+
+ if h1 == h2 && h2 == h3 {
+ t.Errorf("got duplicate hash %d want unique", h1)
+ }
+ })
+
+ t.Run("noaes", func(t *testing.T) {
+ env := ""
+ if *runtime.UseAeshash {
+ env = "GODEBUG=cpu.aes=off"
+ }
+
+ h1 := subprocessHash(t, env)
+ t.Logf("%d", h1)
+ h2 := subprocessHash(t, env)
+ t.Logf("%d", h2)
+ h3 := subprocessHash(t, env)
+ t.Logf("%d", h3)
+
+ if h1 == h2 && h2 == h3 {
+ t.Errorf("got duplicate hash %d want unique", h1)
+ }
+ })
+}
