os: ignore O_TRUNC errors on named pipes and terminal devices on Windows

Prior to Go 1.24, os.OpenFile used to support O_TRUNC on named pipes and
terminal devices, even when the truncation was really ignored. This
behavior was consistent with Unix semantics.

CL 618836 changed the implementation of os.OpenFile on Windows and
unintentionally started returning an error when O_TRUNC was used on such
files.

Fixes #76071

Change-Id: Id10d3d8120ae9aa0548ef05423a172ff4e502ff9
Reviewed-on: https://go-review.googlesource.com/c/go/+/716420
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

diff --git a/src/internal/syscall/windows/at_windows.go b/src/internal/syscall/windows/at_windows.go
index 2890e1fdcfc51129334b43c5e3447a5822567a4d..b7ca8433c2a87a65010390a30df92980c7b56896 100644 (file)
--- a/src/internal/syscall/windows/at_windows.go
+++ b/src/internal/syscall/windows/at_windows.go
@@ -131,6 +131,14 @@ func Openat(dirfd syscall.Handle, name string, flag uint64, perm uint32) (_ sysc
 
        if flag&syscall.O_TRUNC != 0 {
                err = syscall.Ftruncate(h, 0)
+               if err == ERROR_INVALID_PARAMETER {
+                       // ERROR_INVALID_PARAMETER means truncation is not supported on this file handle.
+                       // Unix's O_TRUNC specification says to ignore O_TRUNC on named pipes and terminal devices.
+                       // We do the same here.
+                       if t, err1 := syscall.GetFileType(h); err1 == nil && (t == syscall.FILE_TYPE_PIPE || t == syscall.FILE_TYPE_CHAR) {
+                               err = nil
+                       }
+               }
                if err != nil {
                        syscall.CloseHandle(h)
                        return syscall.InvalidHandle, err

diff --git a/src/os/os_windows_test.go b/src/os/os_windows_test.go
index cd2413d26d4a534357d4ae31d4621e159d38d75b..3e7bddc791154c2003f20463fea8f901e6dd7cdf 100644 (file)
--- a/src/os/os_windows_test.go
+++ b/src/os/os_windows_test.go
@@ -2275,3 +2275,16 @@ func TestOpenFileFlagInvalid(t *testing.T) {
        }
        f.Close()
 }
+
+func TestOpenFileTruncateNamedPipe(t *testing.T) {
+       t.Parallel()
+       name := pipeName()
+       pipe := newBytePipe(t, name, false)
+       defer pipe.Close()
+
+       f, err := os.OpenFile(name, os.O_TRUNC|os.O_RDWR|os.O_CREATE, 0666)
+       if err != nil {
+               t.Fatal(err)
+       }
+       f.Close()
+}

diff --git a/src/os/root_windows_test.go b/src/os/root_windows_test.go
index 8ae6f0c9d34d7451d3a43cd1914a6ab0cb097f97..47643f98d103bd31d9fdc52ef7d2deddcde6ae88 100644 (file)
--- a/src/os/root_windows_test.go
+++ b/src/os/root_windows_test.go
@@ -228,3 +228,22 @@ func TestRootSymlinkToDirectory(t *testing.T) {
                })
        }
 }
+
+func TestRootOpenFileTruncateNamedPipe(t *testing.T) {
+       t.Parallel()
+       name := pipeName()
+       pipe := newBytePipe(t, name, false)
+       defer pipe.Close()
+
+       root, err := os.OpenRoot(filepath.Dir(name))
+       if err != nil {
+               t.Fatal(err)
+       }
+       defer root.Close()
+
+       f, err := root.OpenFile(filepath.Base(name), os.O_TRUNC|os.O_RDWR|os.O_CREATE, 0666)
+       if err != nil {
+               t.Fatal(err)
+       }
+       f.Close()
+}

diff --git a/src/syscall/syscall_windows.go b/src/syscall/syscall_windows.go
index 817eeb681134956e5f0cb918132feaadbe3c790f..3e63897b6bc3a3c36066eccf0a3363a660d3737c 100644 (file)
--- a/src/syscall/syscall_windows.go
+++ b/src/syscall/syscall_windows.go
@@ -468,6 +468,14 @@ func Open(name string, flag int, perm uint32) (fd Handle, err error) {
        if flag&O_TRUNC == O_TRUNC &&
                (createmode == OPEN_EXISTING || (createmode == OPEN_ALWAYS && err == ERROR_ALREADY_EXISTS)) {
                err = Ftruncate(h, 0)
+               if err == _ERROR_INVALID_PARAMETER {
+                       // ERROR_INVALID_PARAMETER means truncation is not supported on this file handle.
+                       // Unix's O_TRUNC specification says to ignore O_TRUNC on named pipes and terminal devices.
+                       // We do the same here.
+                       if t, err1 := GetFileType(h); err1 == nil && (t == FILE_TYPE_PIPE || t == FILE_TYPE_CHAR) {
+                               err = nil
+                       }
+               }
                if err != nil {
                        CloseHandle(h)
                        return InvalidHandle, err

diff --git a/src/syscall/types_windows.go b/src/syscall/types_windows.go
index b40b455e7de9b2091ba2f79bcfc976e7e4c81294..3c6d18a8509e97d99ad121b24d3290e9de0d7090 100644 (file)
--- a/src/syscall/types_windows.go
+++ b/src/syscall/types_windows.go
@@ -34,6 +34,10 @@ const (
        WSAECONNRESET             Errno = 10054
 )
 
+const (
+       _ERROR_INVALID_PARAMETER Errno = 87
+)
+
 const (
        // Invented values to support what package os expects.
        O_RDONLY       = 0x00000