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When running with `--serial pty --console pty --seccomp=false` the SIGWICH listener thread would panic as the seccomp filter was empty. Adopt the mechanism used in the rest of the code and check for non-empty filter before trying to apply it. Signed-off-by: Rob Bradford <robert.bradford@intel.com>
140 lines
3.8 KiB
Rust
140 lines
3.8 KiB
Rust
// Copyright 2021 Alyssa Ross <hi@alyssa.is>
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// SPDX-License-Identifier: Apache-2.0
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use crate::clone3::{clone3, clone_args, CLONE_CLEAR_SIGHAND};
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use libc::{
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c_int, c_void, close, getpgrp, ioctl, pipe2, poll, pollfd, setsid, sigemptyset, siginfo_t,
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sigprocmask, tcsetpgrp, O_CLOEXEC, POLLERR, SIGWINCH, SIG_SETMASK, STDIN_FILENO, STDOUT_FILENO,
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TIOCSCTTY,
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};
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use seccompiler::{apply_filter, BpfProgram};
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use std::cell::RefCell;
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use std::fs::File;
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use std::io::{self, ErrorKind, Read, Write};
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use std::mem::size_of;
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use std::mem::MaybeUninit;
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use std::os::unix::prelude::*;
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use std::process::exit;
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use std::ptr::null_mut;
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use vmm_sys_util::signal::register_signal_handler;
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thread_local! {
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// The tty file descriptor is stored in a global variable so it
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// can be accessed by a signal handler.
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static TX: RefCell<Option<File>> = RefCell::new(None);
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}
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fn with_tx<R, F: FnOnce(&File) -> R>(f: F) -> R {
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TX.with(|tx| f(tx.borrow().as_ref().unwrap()))
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}
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// This function has to be safe to call from a signal handler, and
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// therefore must not panic.
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fn notify() {
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if let Err(e) = with_tx(|mut tx| tx.write_all(b"\n")) {
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if e.kind() == ErrorKind::BrokenPipe {
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exit(0);
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}
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exit(1);
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}
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}
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extern "C" fn sigwinch_handler(_signo: c_int, _info: *mut siginfo_t, _unused: *mut c_void) {
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notify();
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}
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fn unblock_all_signals() -> io::Result<()> {
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let mut set = MaybeUninit::uninit();
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if unsafe { sigemptyset(set.as_mut_ptr()) } == -1 {
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return Err(io::Error::last_os_error());
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}
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let set = unsafe { set.assume_init() };
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if unsafe { sigprocmask(SIG_SETMASK, &set, null_mut()) } == -1 {
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return Err(io::Error::last_os_error());
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}
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Ok(())
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}
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fn sigwinch_listener_main(seccomp_filter: BpfProgram, tx: File, tty: &File) -> ! {
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TX.with(|opt| opt.replace(Some(tx)));
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unsafe {
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close(STDIN_FILENO);
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close(STDOUT_FILENO);
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}
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unblock_all_signals().unwrap();
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if !seccomp_filter.is_empty() {
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apply_filter(&seccomp_filter).unwrap();
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}
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register_signal_handler(SIGWINCH, sigwinch_handler).unwrap();
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unsafe {
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// Create a new session (and therefore a new process group).
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assert_ne!(setsid(), -1);
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// Set the tty to be this process's controlling terminal.
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assert_ne!(ioctl(tty.as_raw_fd(), TIOCSCTTY, 0), -1);
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// Become the foreground process group of the tty.
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assert_ne!(tcsetpgrp(tty.as_raw_fd(), getpgrp()), -1);
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}
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notify();
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// Wait for the pipe to close, indicating the parent has exited.
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with_tx(|tx| {
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let mut pollfd = pollfd {
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fd: tx.as_raw_fd(),
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events: 0,
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revents: 0,
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};
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while unsafe { poll(&mut pollfd, 1, -1) } == -1 {
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let e = io::Error::last_os_error();
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assert!(
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matches!(e.kind(), ErrorKind::Interrupted | ErrorKind::WouldBlock),
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"poll: {}",
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e
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);
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}
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assert_eq!(pollfd.revents, POLLERR);
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});
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exit(0);
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}
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pub fn start_sigwinch_listener(seccomp_filter: BpfProgram, pty: &File) -> io::Result<File> {
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let mut pipe = [-1; 2];
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if unsafe { pipe2(pipe.as_mut_ptr(), O_CLOEXEC) } == -1 {
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return Err(io::Error::last_os_error());
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}
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let mut rx = unsafe { File::from_raw_fd(pipe[0]) };
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let tx = unsafe { File::from_raw_fd(pipe[1]) };
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let mut args = clone_args::default();
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args.flags |= CLONE_CLEAR_SIGHAND;
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match unsafe { clone3(&mut args, size_of::<clone_args>()) } {
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-1 => return Err(io::Error::last_os_error()),
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0 => {
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drop(rx);
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sigwinch_listener_main(seccomp_filter, tx, pty);
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}
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_ => (),
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}
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drop(tx);
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// Wait for a notification indicating readiness.
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rx.read_exact(&mut [0])?;
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Ok(rx)
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}
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