PING^1 [PATCH v8 1/3] Add an internal wrapper for clone, clone2 and clone3

[H.J. Lu]

On Fri, Jun 4, 2021 at 5:20 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Tue, Jun 1, 2021 at 7:55 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > The clone3 system call provides a superset of the functionality of clone
> > and clone2.  It also provides a number of API improvements, including
> > the ability to specify the size of the child's stack area which can be
> > used by kernel to compute the shadow stack size when allocating the
> > shadow stack.  Add:
> >
> > extern int __clone_internal (struct clone_args *__cl_args,
> >                              int (*__func) (void *__arg), void *__arg);
> >
> > to provide an abstract interface for clone, clone2 and clone3.
> >
> > 1. Simplify stack management for thread creation by passing both stack
> > base and size to create_thread.
> > 2. Consolidate clone vs clone2 differences into a single file.
> > 3. Call __clone3 if HAVE_CLONE3_WAPPER is defined.  If __clone3 returns
> > -1 with ENOSYS, fall back to clone or clone2.
> > 4. Use only __clone_internal to clone a thread.  Since the stack size
> > argument for create_thread is now unconditional, always pass stack size
> > to create_thread.
> > 5. Enable the public clone3 wrapper in the future after it has been
> > added to all targets.
> >
> > NB: Sandbox should return ENOSYS on clone3 if it is rejected:
> >
> > https://bugs.chromium.org/p/chromium/issues/detail?id=1213452#c5
>
> The sandbox issue has been fixed by
>
> The following revision refers to this bug:
>   https://chromium.googlesource.com/chromium/src/+/218438259dd795456f0a48f67cbe5b4e520db88b
>
> commit 218438259dd795456f0a48f67cbe5b4e520db88b
> Author: Matthew Denton <mpdenton@chromium.org>
> Date: Thu Jun 03 20:06:13 2021
>
> Linux sandbox: return ENOSYS for clone3
>
> Because clone3 uses a pointer argument rather than a flags argument, we
> cannot examine the contents with seccomp, which is essential to
> preventing sandboxed processes from starting other processes. So, we
> won't be able to support clone3 in Chromium. This CL modifies the
> BPF policy to return ENOSYS for clone3 so glibc always uses the fallback
> to clone.
>
> Bug: 1213452
> Change-Id: I7c7c585a319e0264eac5b1ebee1a45be2d782303
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2936184
> Reviewed-by: Robert Sesek <rsesek@chromium.org>
> Commit-Queue: Matthew Denton <mpdenton@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#888980}
>
> [modify] https://crrev.com/218438259dd795456f0a48f67cbe5b4e520db88b/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc
>
> --
> H.J.

PING.


-- 
H.J.