Skip to content

Only use clone3 when needed for pidfd #89924

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 3 commits into from
Oct 16, 2021
Merged

Only use clone3 when needed for pidfd #89924

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
de2e483
Only use `clone3` when needed for pidfd
cuviper Oct 15, 2021
ad6e5e1
Update another comment on fork vs. clone3
cuviper Oct 15, 2021
74ef530
Also note tool expectations of fork vs clone3
cuviper Oct 15, 2021
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
12 changes: 9 additions & 3 deletions library/std/src/sys/unix/process/process_unix.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -166,14 +166,20 @@ 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.
// Some tools (e.g. sandboxing tools) may also expect `fork`
// rather than `clone3`.
let want_clone3 = 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;

// 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) {
if want_clone3 && HAS_CLONE3.load(Ordering::Relaxed) {
let mut flags = 0;
if self.get_create_pidfd() {
flags |= CLONE_PIDFD;
Expand Down Expand Up @@ -212,8 +218,8 @@ 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))
}

Expand Down