From 0fc0c5a013c929649330e817a787195086e233bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alicia=20Boya=20Garc=C3=ADa?= <aboya@igalia.com>
Date: Wed, 8 Jan 2025 18:15:55 +0100
Subject: [PATCH] Close non-stdio file handles when daemonizing

Otherwise, when the compiler wrapper spawns the sccache server, the
server may end up with unintended file descriptors, which can lead to
unexpected problems.

This is particularly problematic if any of those file descriptors that
accidentally end up in the server process is a pipe, as the pipe will
only be closed when all the processes with that file descriptor close it
or exit.

This was causing sccache to hang ninja, as ninja uses the EOF of a pipe
given to the subprocess to detect when that subprocess has exited:
https://github.com/ninja-build/ninja/issues/2444#issuecomment-2577999973

This patch adds a dependency on the
[close_fds](https://crates.io/crates/close_fds) crate, which
automatically chooses an appropriate mechanism to close a range of file
descriptors. On Linux 5.9+ that mechanism will be libc::close_range().

Fixes https://github.com/mozilla/sccache/issues/2313
---
 Cargo.lock  | 11 +++++++++++
 Cargo.toml  |  1 +
 src/util.rs |  4 ++++
 3 files changed, 16 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 8a79ec0ff..964504e22 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -440,6 +440,16 @@ version = "0.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "702fc72eb24e5a1e48ce58027a675bc24edd52096d5397d4aea7c6dd9eca0bd1"
 
+[[package]]
+name = "close_fds"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3bc416f33de9d59e79e57560f450d21ff8393adcf1cdfc3e6d8fb93d5f88a2ed"
+dependencies = [
+ "cfg-if 1.0.0",
+ "libc",
+]
+
 [[package]]
 name = "colorchoice"
 version = "1.0.0"
@@ -2531,6 +2541,7 @@ dependencies = [
  "cc",
  "chrono",
  "clap",
+ "close_fds",
  "daemonize",
  "directories",
  "encoding_rs",
diff --git a/Cargo.toml b/Cargo.toml
index d29cdbbb1..1226e2063 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -121,6 +121,7 @@ rouille = { version = "3.6", optional = true, default-features = false, features
 ] }
 syslog = { version = "6", optional = true }
 version-compare = { version = "0.1.1", optional = true }
+close_fds = "0.3.2"
 
 [dev-dependencies]
 assert_cmd = "2.0.13"
diff --git a/src/util.rs b/src/util.rs
index 7174681d6..f0ca0f506 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -851,6 +851,10 @@ pub fn daemonize() -> Result<()> {
         Ok(ref val) if val == "1" => {}
         _ => {
             Daemonize::new().start().context("failed to daemonize")?;
+            // Be extra-zealous and clase all non-stdio file descriptors.
+            unsafe {
+                close_fds::close_open_fds(3, &[]);
+            }
         }
     }