os: recognize EFTYPE, EINVAL as a refusal to open a symlink

NetBSD returns EFTYPE when opening a symlink with O_NOFOLLOW.

Dragonfly seems to return EINVAL. Only check for EINVAL on Dragonfly,
since that seems like a bit of a broad net.

Change-Id: I031357816f1fe4c370373001207e65996087597f
Reviewed-on: https://go-review.googlesource.com/c/go/+/630396
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

diff --git a/src/os/eloop_netbsd.go b/src/os/eloop_netbsd.go
new file mode 100644 (file)
index 0000000..670c88a
--- /dev/null
+++ b/src/os/eloop_netbsd.go
@@ -0,0 +1,19 @@
+// Copyright 2024 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.
+
+//go:build netbsd
+
+package os
+
+import "syscall"
+
+// isNoFollowErr reports whether err may result from O_NOFOLLOW blocking an open operation.
+func isNoFollowErr(err error) bool {
+       // NetBSD returns EFTYPE, but check the other possibilities as well.
+       switch err {
+       case syscall.ELOOP, syscall.EMLINK, syscall.EFTYPE:
+               return true
+       }
+       return false
+}

diff --git a/src/os/eloop_other.go b/src/os/eloop_other.go
new file mode 100644 (file)
index 0000000..aace57b
--- /dev/null
+++ b/src/os/eloop_other.go
@@ -0,0 +1,27 @@
+// Copyright 2024 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.
+
+//go:build aix || darwin || dragonfly || freebsd || linux || openbsd || solaris || wasip1
+
+package os
+
+import (
+       "runtime"
+       "syscall"
+)
+
+// isNoFollowErr reports whether err may result from O_NOFOLLOW blocking an open operation.
+func isNoFollowErr(err error) bool {
+       switch err {
+       case syscall.ELOOP, syscall.EMLINK:
+               return true
+       }
+       if runtime.GOOS == "dragonfly" {
+               // Dragonfly appears to return EINVAL from openat in this case.
+               if err == syscall.EINVAL {
+                       return true
+               }
+       }
+       return false
+}

diff --git a/src/os/root_unix.go b/src/os/root_unix.go
index 568c47506eb294d9473b2b061e5012e255f26309..4b52b81de71e815682b883dbbaa1defabad44a73 100644 (file)
--- a/src/os/root_unix.go
+++ b/src/os/root_unix.go
@@ -61,7 +61,7 @@ func openRootInRoot(r *Root, name string) (*Root, error) {
        fd, err := doInRoot(r, name, func(parent int, name string) (fd int, err error) {
                ignoringEINTR(func() error {
                        fd, err = unix.Openat(parent, name, syscall.O_NOFOLLOW|syscall.O_CLOEXEC, 0)
-                       if err == syscall.ELOOP || err == syscall.EMLINK {
+                       if isNoFollowErr(err) {
                                err = checkSymlink(parent, name, err)
                        }
                        return err
@@ -79,7 +79,7 @@ func rootOpenFileNolog(root *Root, name string, flag int, perm FileMode) (*File,
        fd, err := doInRoot(root, name, func(parent int, name string) (fd int, err error) {
                ignoringEINTR(func() error {
                        fd, err = unix.Openat(parent, name, syscall.O_NOFOLLOW|syscall.O_CLOEXEC|flag, uint32(perm))
-                       if err == syscall.ELOOP || err == syscall.ENOTDIR || err == syscall.EMLINK {
+                       if isNoFollowErr(err) || err == syscall.ENOTDIR {
                                err = checkSymlink(parent, name, err)
                        }
                        return err
@@ -100,7 +100,7 @@ func rootOpenDir(parent int, name string) (int, error) {
        )
        ignoringEINTR(func() error {
                fd, err = unix.Openat(parent, name, syscall.O_NOFOLLOW|syscall.O_CLOEXEC|syscall.O_DIRECTORY, 0)
-               if err == syscall.ELOOP || err == syscall.ENOTDIR || err == syscall.EMLINK {
+               if isNoFollowErr(err) || err == syscall.ENOTDIR {
                        err = checkSymlink(parent, name, err)
                } else if err == syscall.ENOTSUP || err == syscall.EOPNOTSUPP {
                        // ENOTSUP and EOPNOTSUPP are often, but not always, the same errno.