Casting to a *uintptr is not ok if there isn't at least 8 bytes of
data backing that pointer (on 64-bit archs).
So although we end up making a slice of 0 length with that pointer,
the cast itself doesn't know that.
Instead, bail early if the result is going to be 0 length.
Fixes #59336
Change-Id: Id3c0e09d341d838835c0382cccfb0f71dc3dc7e6
Reviewed-on: https://go-review.googlesource.com/c/go/+/480575
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
(cherry picked from commit
297cf6dd31bd99fc4ccda320aa3d4faf290ab278)
Reviewed-on: https://go-review.googlesource.com/c/go/+/481238
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
// words returns a []uintptr pointing at the same data as x,
// with any trailing partial word removed.
func words(x []byte) []uintptr {
- return unsafe.Slice((*uintptr)(unsafe.Pointer(&x[0])), uintptr(len(x))/wordSize)
+ n := uintptr(len(x)) / wordSize
+ if n == 0 {
+ // Avoid creating a *uintptr that refers to data smaller than a uintptr;
+ // see issue 59334.
+ return nil
+ }
+ return unsafe.Slice((*uintptr)(unsafe.Pointer(&x[0])), n)
}
func xorLoop[T byte | uintptr](dst, x, y []T) {
--- /dev/null
+// run -tags=purego -gcflags=all=-d=checkptr
+
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "crypto/subtle"
+
+func main() {
+ dst := make([]byte, 5)
+ src := make([]byte, 5)
+ for _, n := range []int{1024, 2048} { // just to make the size non-constant
+ b := make([]byte, n)
+ subtle.XORBytes(dst, src, b[n-5:])
+ }
+}