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Merge pull request #605 from mahkoh/jorth/clone3

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clone3: don't use clone3 syscall directly
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mahkoh 2025-09-16 07:25:48 +02:00 • committed by GitHub
commit ddd96b9ad8
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1 changed files with 47 additions and 64 deletions
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111
src/utils/clone3.rs
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@ -8,22 +8,6 @@ use {
uapi::{Msghdr, MsghdrMut, OwnedFd, c},
};
#[derive(Default, Copy, Clone)]
#[expect(non_camel_case_types, dead_code)]
struct clone_args {
flags: u64,
pidfd: u64,
child_tid: u64,
parent_tid: u64,
exit_signal: u64,
stack: u64,
stack_size: u64,
tls: u64,
set_tid: u64,
set_tid_size: u64,
cgroup: u64,
}
pub enum Forked {
Parent { pid: c::pid_t, pidfd: OwnedFd },
Child { pidfd: Option<OwnedFd> },
@ -32,33 +16,25 @@ pub enum Forked {
const REAPER_VAR: &str = "JAY_REAPER_PID";
pub fn fork_with_pidfd(pidfd_for_child: bool) -> Result<Forked, ForkerError> {
let mut pidfd: c::c_int = 0;
let mut args = clone_args {
flags: c::CLONE_PIDFD as u64,
pidfd: (&mut pidfd as *mut c::c_int) as _,
exit_signal: c::SIGCHLD as _,
..Default::default()
};
let mut child_pidfd = None;
if pidfd_for_child {
child_pidfd = Some(uapi::pidfd_open(uapi::getpid(), 0).unwrap());
}
let (p, c) = uapi::socketpair(c::AF_UNIX, c::SOCK_DGRAM | c::SOCK_CLOEXEC, 0)
.map_err(|e| ForkerError::Socketpair(e.into()))?;
unsafe {
let pid = c::syscall(
c::SYS_clone3,
&mut args as *const _ as usize,
size_of::<clone_args>(),
);
if let Err(e) = uapi::map_err!(pid) {
return Err(ForkerError::Fork(e.into()));
}
let pid = uapi::fork().map_err(|e| ForkerError::Fork(e.into()))?;
let res = if pid == 0 {
drop(p);
env::remove_var(REAPER_VAR);
let pidfd = uapi::pidfd_open(uapi::getpid(), 0).unwrap();
send_pidfd(&c, &pidfd);
Forked::Child { pidfd: child_pidfd }
} else {
drop(c);
Forked::Parent {
pid: pid as _,
pidfd: OwnedFd::new(pidfd),
pidfd: recv_pidfd(&p)?,
}
};
Ok(res)
@ -71,47 +47,17 @@ pub fn double_fork() -> Result<Option<OwnedFd>, ForkerError> {
match fork_with_pidfd(false)? {
Forked::Parent { pid, .. } => {
drop(c);
let mut buf = [MaybeUninit::<u8>::uninit(); 128];
let iov: &mut [&mut [u8]] = &mut [];
let mut msghdr = MsghdrMut {
iov,
control: Some(&mut buf),
name: uapi::sockaddr_none_mut(),
flags: 0,
};
let _wait = OnDrop(|| {
let _ = uapi::waitpid(pid, 0);
});
let (_, _, mut ctrl) = uapi::recvmsg(p.raw(), &mut msghdr, c::MSG_CMSG_CLOEXEC)
.map_err(|e| ForkerError::RecvPidfd(e.into()))?;
let (_, hdr, data) =
uapi::cmsg_read(&mut ctrl).map_err(|e| ForkerError::CmsgRead(e.into()))?;
if hdr.cmsg_level != c::SOL_SOCKET || hdr.cmsg_type != c::SCM_RIGHTS {
return Err(ForkerError::InvalidCmsg);
}
let Ok(fd) = uapi::pod_read(data) else {
return Err(ForkerError::InvalidCmsg);
};
Ok(Some(OwnedFd::new(fd)))
recv_pidfd(&p).map(Some)
}
Forked::Child { .. } => {
drop(p);
if let Ok(f) = fork_with_pidfd(true) {
match f {
Forked::Parent { pidfd, .. } => {
let pidfd = pidfd.raw();
let mut buf = [MaybeUninit::uninit(); 128];
let mut hdr: c::cmsghdr = uapi::pod_zeroed();
hdr.cmsg_level = c::SOL_SOCKET;
hdr.cmsg_type = c::SCM_RIGHTS;
let _ = uapi::cmsg_write(&mut &mut buf[..], hdr, &pidfd);
let iov: &[&[u8]] = &[];
let msghdr = Msghdr {
iov,
control: Some(&buf[..uapi::cmsg_space(size_of_val(&pidfd))]),
name: uapi::sockaddr_none_ref(),
};
let _ = uapi::sendmsg(c.raw(), &msghdr, 0);
send_pidfd(&c, &pidfd);
}
Forked::Child { pidfd } => {
let pidfd = pidfd.unwrap();
@ -176,3 +122,40 @@ fn set_deathsig() {
c::prctl(c::PR_SET_PDEATHSIG, c::SIGKILL as c::c_ulong);
}
}
fn send_pidfd(socket: &OwnedFd, pidfd: &OwnedFd) {
let pidfd = pidfd.raw();
let mut buf = [MaybeUninit::uninit(); 128];
let mut hdr: c::cmsghdr = uapi::pod_zeroed();
hdr.cmsg_level = c::SOL_SOCKET;
hdr.cmsg_type = c::SCM_RIGHTS;
let _ = uapi::cmsg_write(&mut &mut buf[..], hdr, &pidfd);
let iov: &[&[u8]] = &[];
let msghdr = Msghdr {
iov,
control: Some(&buf[..uapi::cmsg_space(size_of_val(&pidfd))]),
name: uapi::sockaddr_none_ref(),
};
let _ = uapi::sendmsg(socket.raw(), &msghdr, 0);
}
fn recv_pidfd(socket: &OwnedFd) -> Result<OwnedFd, ForkerError> {
let mut buf = [MaybeUninit::<u8>::uninit(); 128];
let iov: &mut [&mut [u8]] = &mut [];
let mut msghdr = MsghdrMut {
iov,
control: Some(&mut buf),
name: uapi::sockaddr_none_mut(),
flags: 0,
};
let (_, _, mut ctrl) = uapi::recvmsg(socket.raw(), &mut msghdr, c::MSG_CMSG_CLOEXEC)
.map_err(|e| ForkerError::RecvPidfd(e.into()))?;
let (_, hdr, data) = uapi::cmsg_read(&mut ctrl).map_err(|e| ForkerError::CmsgRead(e.into()))?;
if hdr.cmsg_level != c::SOL_SOCKET || hdr.cmsg_type != c::SCM_RIGHTS {
return Err(ForkerError::InvalidCmsg);
}
let Ok(fd) = uapi::pod_read(data) else {
return Err(ForkerError::InvalidCmsg);
};
Ok(OwnedFd::new(fd))
}