From 57769b5532e96a8f6b705035a39ee056a22e04c3 Mon Sep 17 00:00:00 2001
From: Richard Miller <millerresearch@gmail.com>
Date: Thu, 4 Sep 2025 11:42:56 +0100
Subject: [PATCH] os: reject OpenDir of a non-directory file in Plan 9

Check that the path argument to OpenDir in Plan 9 is a directory,
and return error syscall.ENOTDIR if it is not.

Fixes #75196

Change-Id: I3bec6b6b40a38c21264b5d22ff3e7dfbf8c1c6d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/700855
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
---
 src/os/file_plan9.go | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/os/file_plan9.go b/src/os/file_plan9.go
index 17026409eb6..e563d123efa 100644
--- a/src/os/file_plan9.go
+++ b/src/os/file_plan9.go
@@ -135,7 +135,20 @@ func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
 }
 
 func openDirNolog(name string) (*File, error) {
-	return openFileNolog(name, O_RDONLY, 0)
+	f, e := openFileNolog(name, O_RDONLY, 0)
+	if e != nil {
+		return nil, e
+	}
+	d, e := f.Stat()
+	if e != nil {
+		f.Close()
+		return nil, e
+	}
+	if !d.IsDir() {
+		f.Close()
+		return nil, &PathError{Op: "open", Path: name, Err: syscall.ENOTDIR}
+	}
+	return f, nil
 }
 
 // Close closes the File, rendering it unusable for I/O.