From 1e638101df598a2021589b119c659547ca236d51 Mon Sep 17 00:00:00 2001
From: F Y <x1f604@gmail.com>
Date: Tue, 17 Oct 2023 10:01:27 +0100
Subject: [PATCH] unix: stop counting trailing NUL for abstract addresses
 starting with NUL

Changes trailing-NUL-counting behavior for abstract addresses
starting with the NUL character to be the same as abstract
addresses starting with the @ character.

For golang/go#63579.

Change-Id: I2f26de4bcf614c4635ad188b1afa3d14ebd9a95f
Reviewed-on: https://go-review.googlesource.com/c/sys/+/535955
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---
 unix/syscall_aix.go                 |  3 ++-
 unix/syscall_internal_linux_test.go | 12 +++++++++++-
 unix/syscall_linux.go               |  3 ++-
 unix/syscall_solaris.go             |  3 ++-
 windows/syscall_windows.go          |  3 ++-
 5 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/unix/syscall_aix.go b/unix/syscall_aix.go
index 6d3009d21..67ce6cef2 100644
--- a/unix/syscall_aix.go
+++ b/unix/syscall_aix.go
@@ -106,7 +106,8 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	if n > 0 {
 		sl += _Socklen(n) + 1
 	}
-	if sa.raw.Path[0] == '@' {
+	if sa.raw.Path[0] == '@' || (sa.raw.Path[0] == 0 && sl > 3) {
+		// Check sl > 3 so we don't change unnamed socket behavior.
 		sa.raw.Path[0] = 0
 		// Don't count trailing NUL for abstract address.
 		sl--
diff --git a/unix/syscall_internal_linux_test.go b/unix/syscall_internal_linux_test.go
index 7d34c4f1e..e8b749170 100644
--- a/unix/syscall_internal_linux_test.go
+++ b/unix/syscall_internal_linux_test.go
@@ -517,7 +517,7 @@ func TestSockaddrUnix_sockaddr(t *testing.T) {
 			slen: 2, // family (uint16)
 		},
 		{
-			name: "abstract",
+			name: "abstract_starting_with_at",
 			sa: &SockaddrUnix{
 				Name: "@",
 			},
@@ -526,6 +526,16 @@ func TestSockaddrUnix_sockaddr(t *testing.T) {
 			},
 			slen: 3, // family (uint16) + NULL
 		},
+		{
+			name: "abstract_starting_with_null",
+			sa: &SockaddrUnix{
+				Name: "\x00",
+			},
+			raw: &RawSockaddrUnix{
+				Family: AF_UNIX,
+			},
+			slen: 3, // family (uint16) + NULL
+		},
 		{
 			name: "named",
 			sa: &SockaddrUnix{
diff --git a/unix/syscall_linux.go b/unix/syscall_linux.go
index 6b8a4ad69..a5e1c10e3 100644
--- a/unix/syscall_linux.go
+++ b/unix/syscall_linux.go
@@ -417,7 +417,8 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	if n > 0 {
 		sl += _Socklen(n) + 1
 	}
-	if sa.raw.Path[0] == '@' {
+	if sa.raw.Path[0] == '@' || (sa.raw.Path[0] == 0 && sl > 3) {
+		// Check sl > 3 so we don't change unnamed socket behavior.
 		sa.raw.Path[0] = 0
 		// Don't count trailing NUL for abstract address.
 		sl--
diff --git a/unix/syscall_solaris.go b/unix/syscall_solaris.go
index b99cfa134..60c8142d4 100644
--- a/unix/syscall_solaris.go
+++ b/unix/syscall_solaris.go
@@ -128,7 +128,8 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	if n > 0 {
 		sl += _Socklen(n) + 1
 	}
-	if sa.raw.Path[0] == '@' {
+	if sa.raw.Path[0] == '@' || (sa.raw.Path[0] == 0 && sl > 3) {
+		// Check sl > 3 so we don't change unnamed socket behavior.
 		sa.raw.Path[0] = 0
 		// Don't count trailing NUL for abstract address.
 		sl--
diff --git a/windows/syscall_windows.go b/windows/syscall_windows.go
index dcaa40977..fb6cfd046 100644
--- a/windows/syscall_windows.go
+++ b/windows/syscall_windows.go
@@ -970,7 +970,8 @@ func (sa *SockaddrUnix) sockaddr() (unsafe.Pointer, int32, error) {
 	if n > 0 {
 		sl += int32(n) + 1
 	}
-	if sa.raw.Path[0] == '@' {
+	if sa.raw.Path[0] == '@' || (sa.raw.Path[0] == 0 && sl > 3) {
+		// Check sl > 3 so we don't change unnamed socket behavior.
 		sa.raw.Path[0] = 0
 		// Don't count trailing NUL for abstract address.
 		sl--