From 85b55ce00df3766db2b617bda4b2457f6d76e542 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 15 Oct 2021 12:21:45 -0700 Subject: [PATCH 1/4] Only use `clone3` when needed for pidfd In #89522 we learned that `clone3` is interacting poorly with Gentoo's `sandbox` tool. We only need that for the unstable pidfd extensions, so otherwise avoid that and use a normal `fork`. --- library/std/src/sys/unix/process/process_unix.rs | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/library/std/src/sys/unix/process/process_unix.rs b/library/std/src/sys/unix/process/process_unix.rs index 99013efb495d0..d0af2b6e9db0c 100644 --- a/library/std/src/sys/unix/process/process_unix.rs +++ b/library/std/src/sys/unix/process/process_unix.rs @@ -166,6 +166,10 @@ impl Command { fn clone3(cl_args: *mut clone_args, len: libc::size_t) -> libc::c_long } + // Bypassing libc for `clone3` can make further libc calls unsafe, + // so we use it sparingly for now. See #89522 for details. + let want_clone3_pidfd = self.get_create_pidfd(); + // If we fail to create a pidfd for any reason, this will // stay as -1, which indicates an error. let mut pidfd: pid_t = -1; @@ -173,14 +177,9 @@ impl Command { // Attempt to use the `clone3` syscall, which supports more arguments // (in particular, the ability to create a pidfd). If this fails, // we will fall through this block to a call to `fork()` - if HAS_CLONE3.load(Ordering::Relaxed) { - let mut flags = 0; - if self.get_create_pidfd() { - flags |= CLONE_PIDFD; - } - + if want_clone3_pidfd && HAS_CLONE3.load(Ordering::Relaxed) { let mut args = clone_args { - flags, + flags: CLONE_PIDFD, pidfd: &mut pidfd as *mut pid_t as u64, child_tid: 0, parent_tid: 0, From fa2eee7bf2bcf03f64aa40a25f885b0301a9eb4a Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 15 Oct 2021 14:45:23 -0700 Subject: [PATCH 2/4] Update another comment on fork vs. clone3 --- library/std/src/sys/unix/process/process_unix.rs | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/library/std/src/sys/unix/process/process_unix.rs b/library/std/src/sys/unix/process/process_unix.rs index d0af2b6e9db0c..5e4eff75894b6 100644 --- a/library/std/src/sys/unix/process/process_unix.rs +++ b/library/std/src/sys/unix/process/process_unix.rs @@ -211,8 +211,8 @@ impl Command { } } - // If we get here, the 'clone3' syscall does not exist - // or we do not have permission to call it + // Generally, we just call `fork`. If we get here after wanting `clone3`, + // then the syscall does not exist or we do not have permission to call it. cvt(libc::fork()).map(|res| (res, pidfd)) } From 6edaaa6db80a1d35a9ecb48a3a9b32551b91dc5d Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 15 Oct 2021 15:29:15 -0700 Subject: [PATCH 3/4] Also note tool expectations of fork vs clone3 Co-authored-by: Josh Triplett --- library/std/src/sys/unix/process/process_unix.rs | 2 ++ 1 file changed, 2 insertions(+) diff --git a/library/std/src/sys/unix/process/process_unix.rs b/library/std/src/sys/unix/process/process_unix.rs index 5e4eff75894b6..326382d9038a8 100644 --- a/library/std/src/sys/unix/process/process_unix.rs +++ b/library/std/src/sys/unix/process/process_unix.rs @@ -168,6 +168,8 @@ impl Command { // Bypassing libc for `clone3` can make further libc calls unsafe, // so we use it sparingly for now. See #89522 for details. + // Some tools (e.g. sandboxing tools) may also expect `fork` + // rather than `clone3`. let want_clone3_pidfd = self.get_create_pidfd(); // If we fail to create a pidfd for any reason, this will From e96a0a8681998caf78093b65e746bfd967cb87e9 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 15 Oct 2021 16:04:52 -0700 Subject: [PATCH 4/4] Revert "Do not call getpid wrapper after fork in tests" This reverts commit 12fbabd27f700a59d0e7031f0839b220c3514bcb. It was only needed because of using raw `clone3` instead of `fork`, but we only do that now when a pidfd is requested. --- src/test/ui/command/command-pre-exec.rs | 25 +++++-------------- .../ui/process/process-panic-after-fork.rs | 17 +------------ 2 files changed, 7 insertions(+), 35 deletions(-) diff --git a/src/test/ui/command/command-pre-exec.rs b/src/test/ui/command/command-pre-exec.rs index 10a8b19159e02..61914e2293070 100644 --- a/src/test/ui/command/command-pre-exec.rs +++ b/src/test/ui/command/command-pre-exec.rs @@ -8,6 +8,8 @@ // ignore-sgx no processes #![feature(process_exec, rustc_private)] +extern crate libc; + use std::env; use std::io::Error; use std::os::unix::process::CommandExt; @@ -15,23 +17,6 @@ use std::process::Command; use std::sync::atomic::{AtomicUsize, Ordering}; use std::sync::Arc; -#[cfg(not(target_os = "linux"))] -fn getpid() -> u32 { - use std::process; - process::id() -} - -/// We need to directly use the getpid syscall instead of using `process::id()` -/// because the libc wrapper might return incorrect values after a process was -/// forked. -#[cfg(target_os = "linux")] -fn getpid() -> u32 { - extern crate libc; - unsafe { - libc::syscall(libc::SYS_getpid) as _ - } -} - fn main() { if let Some(arg) = env::args().nth(1) { match &arg[..] { @@ -83,12 +68,14 @@ fn main() { }; assert_eq!(output.raw_os_error(), Some(102)); - let pid = getpid(); + let pid = unsafe { libc::getpid() }; + assert!(pid >= 0); let output = unsafe { Command::new(&me) .arg("empty") .pre_exec(move || { - let child = getpid(); + let child = libc::getpid(); + assert!(child >= 0); assert!(pid != child); Ok(()) }) diff --git a/src/test/ui/process/process-panic-after-fork.rs b/src/test/ui/process/process-panic-after-fork.rs index ad749371beac0..1ccf6bb051c20 100644 --- a/src/test/ui/process/process-panic-after-fork.rs +++ b/src/test/ui/process/process-panic-after-fork.rs @@ -23,21 +23,6 @@ use std::sync::atomic::{AtomicU32, Ordering}; use libc::c_int; -#[cfg(not(target_os = "linux"))] -fn getpid() -> u32 { - process::id() -} - -/// We need to directly use the getpid syscall instead of using `process::id()` -/// because the libc wrapper might return incorrect values after a process was -/// forked. -#[cfg(target_os = "linux")] -fn getpid() -> u32 { - unsafe { - libc::syscall(libc::SYS_getpid) as _ - } -} - /// This stunt allocator allows us to spot heap allocations in the child. struct PidChecking { parent: A, @@ -59,7 +44,7 @@ impl PidChecking { fn check(&self) { let require_pid = self.require_pid.load(Ordering::Acquire); if require_pid != 0 { - let actual_pid = getpid(); + let actual_pid = process::id(); if require_pid != actual_pid { unsafe { libc::raise(libc::SIGUSR1);