From ee0bd6c69ee01caf076e5c9f7461fe09fa8cf9ba Mon Sep 17 00:00:00 2001
From: Jacob Young <jacobly@ziglang.org>
Date: Fri, 25 Sep 2026 10:00:39 -0400
Subject: [PATCH] Io: avoid leaking inherited descriptors

---
 lib/std/Io.zig          | 17 +++++++++++++++++
 lib/std/Io/Threaded.zig | 40 ++++++++++++++++++++++++++++++++++++++++
 test/src/Runner.zig     | 24 +++++++++++++++++++-----
 3 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/lib/std/Io.zig b/lib/std/Io.zig
index c7f94cbb9652fd9e98f6b419d629c6fc55b292e2..759855179a6e99e770afc2be497774b9e5b21cd2 100644
--- a/lib/std/Io.zig
+++ b/lib/std/Io.zig
@@ -218,6 +218,8 @@ pub const VTable = struct {
     childKill: *const fn (?*anyopaque, *std.process.Child) void,
 
     progressParentFile: *const fn (?*anyopaque) std.Progress.ParentFileError!File,
+    inheritParentDir: *const fn (?*anyopaque, handle: Dir.Handle) (Cancelable || UnexpectedError)!Dir,
+    inheritParentFile: *const fn (?*anyopaque, handle: File.Handle, flags: File.Flags) (Cancelable || UnexpectedError)!File,
 
     now: *const fn (?*anyopaque, Clock) Timestamp,
     clockResolution: *const fn (?*anyopaque, Clock) Clock.ResolutionError!Duration,
@@ -2800,6 +2802,8 @@ pub const failing: std.Io = .{
         .childKill = unreachableChildKill,
 
         .progressParentFile = failingProgressParentFile,
+        .inheritParentDir = unreachableInheritParentDir,
+        .inheritParentFile = unreachableInheritParentFile,
 
         .random = noRandom,
         .randomSecure = failingRandomSecure,
@@ -3470,6 +3474,19 @@ pub fn failingProgressParentFile(userdata: ?*anyopaque) std.Progress.ParentFileE
     return error.UnsupportedOperation;
 }
 
+pub fn unreachableInheritParentDir(userdata: ?*anyopaque, handle: Dir.Handle) (Cancelable || UnexpectedError)!Dir {
+    _ = userdata;
+    _ = handle;
+    unreachable;
+}
+
+pub fn unreachableInheritParentFile(userdata: ?*anyopaque, handle: File.Handle, flags: File.Flags) (Cancelable || UnexpectedError)!File {
+    _ = userdata;
+    _ = handle;
+    _ = flags;
+    unreachable;
+}
+
 pub fn noRandom(userdata: ?*anyopaque, buffer: []u8) void {
     _ = userdata;
     @memset(buffer, 0);
diff --git a/lib/std/Io/Threaded.zig b/lib/std/Io/Threaded.zig
index 2223d3e0659e50bea6a75595bb781596721c37c4..00f29608098c8942e621ba96d6e81e906b463d0f 100644
--- a/lib/std/Io/Threaded.zig
+++ b/lib/std/Io/Threaded.zig
@@ -1906,6 +1906,8 @@ pub fn io(t: *Threaded) Io {
             .childKill = childKill,
 
             .progressParentFile = progressParentFile,
+            .inheritParentDir = inheritParentDir,
+            .inheritParentFile = inheritParentFile,
 
             .now = now,
             .clockResolution = clockResolution,
@@ -17694,6 +17696,44 @@ fn progressParentFile(userdata: ?*anyopaque) std.Progress.ParentFileError!File {
     return t.environ.zig_progress_file;
 }
 
+fn inheritParentHandle(handle: posix.fd_t) Io.InheritParentHandleError!void {
+    switch (native_os) {
+        .linux,
+        .dragonfly,
+        .freebsd,
+        .netbsd,
+        .openbsd,
+        .illumos,
+        .driverkit,
+        .ios,
+        .maccatalyst,
+        .macos,
+        .tvos,
+        .visionos,
+        .watchos,
+        => return setCloexec(handle),
+        else => return error.UnsupportedOperation,
+    }
+}
+
+fn inheritParentDir(userdata: ?*anyopaque, handle: Dir.Handle) Io.InheritParentHandleError!Dir {
+    const t: *Threaded = @ptrCast(@alignCast(userdata));
+    _ = t;
+    try inheritParentHandle(handle);
+    return .{ .handle = handle };
+}
+
+fn inheritParentFile(
+    userdata: ?*anyopaque,
+    handle: File.Handle,
+    flags: File.Flags,
+) Io.InheritParentHandleError!File {
+    const t: *Threaded = @ptrCast(@alignCast(userdata));
+    _ = t;
+    try inheritParentHandle(handle);
+    return .{ .handle = handle, .flags = flags };
+}
+
 pub fn environString(t: *Threaded, comptime name: []const u8) ?[:0]const u8 {
     t.scanEnviron();
     return @field(t.environ.string, name);
diff --git a/test/src/Runner.zig b/test/src/Runner.zig
index c985ff8410fea3e0181a74d41d19be62d36767d0..8a7b3832a41b014de1d86626fe9b8bdd686ec15e 100644
--- a/test/src/Runner.zig
+++ b/test/src/Runner.zig
@@ -132,8 +132,15 @@ pub fn runServer(runner: *Runner) ProtocolError {
                                 args_body[args_body_offset..][0..@sizeOf(std.Io.Dir.Handle)],
                             );
                             args_body_offset += @sizeOf(std.Io.Dir.Handle);
-                            const dir: std.Io.Dir = .{
-                                .handle = dir_handle.*,
+                            const dir = runner.io.vtable.inheritParentDir(
+                                runner.io.userdata,
+                                dir_handle.*,
+                            ) catch |err| switch (err) {
+                                error.Canceled => |e| return e,
+                                error.Unexpected => |e| return runner.fail(
+                                    "unable to inherit parent dir: {t}",
+                                    .{e},
+                                ),
                             };
                             switch (state) {
                                 .positional => {
@@ -171,9 +178,16 @@ pub fn runServer(runner: *Runner) ProtocolError {
                                 args_body[args_body_offset..][0..@sizeOf(std.Io.File.Handle)],
                             );
                             args_body_offset += @sizeOf(std.Io.File.Handle);
-                            const file: std.Io.File = .{
-                                .handle = file_handle.*,
-                                .flags = .{ .nonblocking = false },
+                            const file = runner.io.vtable.inheritParentFile(
+                                runner.io.userdata,
+                                file_handle.*,
+                                .{ .nonblocking = false },
+                            ) catch |err| switch (err) {
+                                error.Canceled => |e| return e,
+                                error.Unexpected => |e| return runner.fail(
+                                    "unable to inherit parent file: {t}",
+                                    .{e},
+                                ),
                             };
                             switch (state) {
                                 .positional => {
-- 
2.54.0