cmd/compile,runtime: panic when unsafe.Slice param is nil and sizeof(…

…elem) == 0 and > 0

Fixes golang#54092

src/cmd/compile/internal/walk/builtin.go

@@ -682,6 +682,25 @@ func walkUnsafeSlice(n *ir.BinaryExpr, init *ir.Nodes) ir.Node {
 		nif.Body.Append(mkcall("panicunsafeslicelen", nil, &nif.Body))
 		appendWalkStmt(init, nif)
 
+		if sliceType.Elem().Size() == 0 {
+			// if ptr == nil && len > 0  {
+			//      panicunsafesliceptrnil()
+			// }
+			nifPtr := ir.NewIfStmt(base.Pos, nil, nil, nil)
+			isNil := ir.NewBinaryExpr(base.Pos, ir.OEQ, unsafePtr, typecheck.NodNil())
+			gtZero := ir.NewBinaryExpr(base.Pos, ir.OGT, typecheck.Conv(len, lenType), ir.NewInt(0))
+			nifPtr.Cond =
+				ir.NewLogicalExpr(base.Pos, ir.OANDAND, isNil, gtZero)
+			nifPtr.Body.Append(mkcall("panicunsafeslicenilptr", nil, &nifPtr.Body))
+			appendWalkStmt(init, nifPtr)
+
+			h := ir.NewSliceHeaderExpr(n.Pos(), sliceType,
+				typecheck.Conv(ptr, types.Types[types.TUNSAFEPTR]),
+				typecheck.Conv(len, types.Types[types.TINT]),
+				typecheck.Conv(len, types.Types[types.TINT]))
+			return walkExpr(typecheck.Expr(h), init)
+		}
+
 		// mem, overflow := runtime.mulUintptr(et.size, len)
 		mem := typecheck.Temp(types.Types[types.TUINTPTR])
 		overflow := typecheck.Temp(types.Types[types.TBOOL])

src/runtime/crash_test.go

@@ -844,3 +844,11 @@ func TestPanicWhilePanicking(t *testing.T) {
 		}
 	}
 }
+
+func TestPanicOnUnsafeSlice(t *testing.T) {
+	output := runTestProg(t, "testprog", "panicOnNilAndEleSizeIsZero")
+	want := "panic: runtime error: unsafe.Slice: ptr is nil and len is not zero"
+	if !strings.Contains(output, want) {
+		t.Errorf("output does not contain %q:\n%s", want, output)
+	}
+}

src/runtime/slice.go

@@ -129,6 +129,12 @@ func unsafeslice(et *_type, ptr unsafe.Pointer, len int) {
 		panicunsafeslicelen()
 	}
 
+	if et.size == 0 {
+		if ptr == nil && len > 0  {
+			panicunsafeslicenilptr()
+		}
+	}
+
 	mem, overflow := math.MulUintptr(et.size, uintptr(len))
 	if overflow || mem > -uintptr(ptr) {
 		if ptr == nil {

src/runtime/testdata/testprog/unsafe.go

@@ -0,0 +1,12 @@
+package main
+
+import "unsafe"
+
+func init() {
+	register("panicOnNilAndEleSizeIsZero", panicOnNilAndEleSizeIsZero)
+}
+
+func panicOnNilAndEleSizeIsZero() {
+	var p *struct{}
+	_ = unsafe.Slice(p, 5)
+}