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vmm: device_manager: Update virtio-console for proper PTY support

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Given the virtio-console is now able to buffer its output when no PTY is
connected on the other end, the device manager code is updated to enable
this. Moving the endpoint type from FilePair to PtyPair enables the
proper codepath in the virtio-console implementation, as well as
updating the PTY resize code, and forcing the PTY to always be
non-blocking.

The non-blocking behavior is required to avoid blocking the guest that
would be waiting on the virtio-console driver. When receiving an
EWOULDBLOCK error, the output will simply be redirected to the temporary
buffer so that it can be later flushed.

The PTY resize logic has been slightly modified to ensure the PTY file
descriptors are closed. It avoids the child process to keep a hold onto
the PTY device, which would have caused the PTY to believe something is
connected on the other end, which would have prevented the detection of
any new connection on the PTY.

Fixes #4521

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
This commit is contained in:
Sebastien Boeuf 2022-08-25 10:50:05 +02:00
parent a391bce781
commit 8c02648ac9
2 changed files with 25 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
vmm/src/device_manager.rs
View File

@ -483,7 +483,7 @@ const DEVICE_MANAGER_ACPI_SIZE: usize = 0x10;
const TIOCSPTLCK: libc::c_int = 0x4004_5431;
const TIOCGTPEER: libc::c_int = 0x5441;
pub fn create_pty(non_blocking: bool) -> io::Result<(File, File, PathBuf)> {
pub fn create_pty() -> io::Result<(File, File, PathBuf)> {
// Try to use /dev/pts/ptmx first then fall back to /dev/ptmx
// This is done to try and use the devpts filesystem that
// could be available for use in the process's namespace first.
@ -492,7 +492,7 @@ pub fn create_pty(non_blocking: bool) -> io::Result<(File, File, PathBuf)> {
// See https://www.kernel.org/doc/Documentation/filesystems/devpts.txt
// for further details.
let custom_flags = libc::O_NOCTTY | if non_blocking { libc::O_NONBLOCK } else { 0 };
let custom_flags = libc::O_NONBLOCK;
let main = match OpenOptions::new()
.read(true)
.write(true)
@ -1864,7 +1864,7 @@ impl DeviceManager {
self.modify_mode(f.as_raw_fd(), |t| unsafe { cfmakeraw(t) })
}
fn listen_for_sigwinch_on_tty(&mut self, pty: &File) -> std::io::Result<()> {
fn listen_for_sigwinch_on_tty(&mut self, pty_main: File, pty_sub: File) -> std::io::Result<()> {
let seccomp_filter = get_seccomp_filter(
&self.seccomp_action,
Thread::PtyForeground,
@ -1872,7 +1872,7 @@ impl DeviceManager {
)
.unwrap();
match start_sigwinch_listener(seccomp_filter, pty) {
match start_sigwinch_listener(seccomp_filter, pty_main, pty_sub) {
Ok(pipe) => {
self.console_resize_pipe = Some(Arc::new(pipe));
}
@ -1903,18 +1903,19 @@ impl DeviceManager {
let file = pty.main.try_clone().unwrap();
self.console_pty = Some(Arc::new(Mutex::new(pty)));
self.console_resize_pipe = resize_pipe.map(Arc::new);
Endpoint::FilePair(file.try_clone().unwrap(), file)
Endpoint::PtyPair(file.try_clone().unwrap(), file)
} else {
let (main, mut sub, path) =
create_pty(false).map_err(DeviceManagerError::ConsolePtyOpen)?;
create_pty().map_err(DeviceManagerError::ConsolePtyOpen)?;
self.set_raw_mode(&mut sub)
.map_err(DeviceManagerError::SetPtyRaw)?;
self.config.lock().unwrap().console.file = Some(path.clone());
let file = main.try_clone().unwrap();
assert!(resize_pipe.is_none());
self.listen_for_sigwinch_on_tty(&sub).unwrap();
self.listen_for_sigwinch_on_tty(main.try_clone().unwrap(), sub)
.unwrap();
self.console_pty = Some(Arc::new(Mutex::new(PtyPair { main, path })));
Endpoint::FilePair(file.try_clone().unwrap(), file)
Endpoint::PtyPair(file.try_clone().unwrap(), file)
}
}
ConsoleOutputMode::Tty => {
@ -2010,7 +2011,7 @@ impl DeviceManager {
self.serial_pty = Some(Arc::new(Mutex::new(pty)));
} else {
let (main, mut sub, path) =
create_pty(true).map_err(DeviceManagerError::SerialPtyOpen)?;
create_pty().map_err(DeviceManagerError::SerialPtyOpen)?;
self.set_raw_mode(&mut sub)
.map_err(DeviceManagerError::SetPtyRaw)?;
self.config.lock().unwrap().serial.file = Some(path.clone());

20
vmm/src/sigwinch_listener.rs
View File

@ -57,9 +57,11 @@ fn unblock_all_signals() -> io::Result<()> {
Ok(())
}
fn sigwinch_listener_main(seccomp_filter: BpfProgram, tx: File, tty: &File) -> ! {
fn sigwinch_listener_main(seccomp_filter: BpfProgram, tx: File, pty: File) -> ! {
TX.with(|opt| opt.replace(Some(tx)));
let pty_fd = pty.into_raw_fd();
unsafe {
close(STDIN_FILENO);
close(STDOUT_FILENO);
@ -78,10 +80,13 @@ fn sigwinch_listener_main(seccomp_filter: BpfProgram, tx: File, tty: &File) -> !
assert_ne!(setsid(), -1);
// Set the tty to be this process's controlling terminal.
assert_ne!(ioctl(tty.as_raw_fd(), TIOCSCTTY, 0), -1);
assert_ne!(ioctl(pty_fd, TIOCSCTTY, 0), -1);
// Become the foreground process group of the tty.
assert_ne!(tcsetpgrp(tty.as_raw_fd(), getpgrp()), -1);
assert_ne!(tcsetpgrp(pty_fd, getpgrp()), -1);
// Close the PTY fd
assert_ne!(close(pty_fd), -1);
}
notify();
@ -109,7 +114,11 @@ fn sigwinch_listener_main(seccomp_filter: BpfProgram, tx: File, tty: &File) -> !
exit(0);
}
pub fn start_sigwinch_listener(seccomp_filter: BpfProgram, pty: &File) -> io::Result<File> {
pub fn start_sigwinch_listener(
seccomp_filter: BpfProgram,
pty_main: File,
pty_sub: File,
) -> io::Result<File> {
let mut pipe = [-1; 2];
if unsafe { pipe2(pipe.as_mut_ptr(), O_CLOEXEC) } == -1 {
return Err(io::Error::last_os_error());
@ -125,7 +134,8 @@ pub fn start_sigwinch_listener(seccomp_filter: BpfProgram, pty: &File) -> io::Re
-1 => return Err(io::Error::last_os_error()),
0 => {
drop(rx);
sigwinch_listener_main(seccomp_filter, tx, pty);
drop(pty_main);
sigwinch_listener_main(seccomp_filter, tx, pty_sub);
}
_ => (),
}