linux-kernel - [PATCH 0/2] ptrace: Making the ptrace changes atomic

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Message-ID: <87tubyx0rg.fsf_-_@email.froward.int.ebiederm.org>
Date:   Tue, 15 Mar 2022 18:18:59 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     <linux-kernel@...r.kernel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexey Gladkov <legion@...nel.org>,
        Kyle Huey <me@...ehuey.com>, Oleg Nesterov <oleg@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Al Viro <viro@...IV.linux.org.uk>, <linux-api@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 0/2] ptrace: Making the ptrace changes atomic

While working on cleaning up the exit path it have had occasion to look
at what guarantees are provided for setting and reading the fields that
are provided in task_struct for ptraces.  Namely exit_code,
ptrace_message, and last_siginfo. It turns out as the ptrace interface
in the kernel was extended in the kernel the old existing interfaces
in the kernel were just wrapped and not properly updated to handle
the new functionality.  This lead to races and inconsistencies.

This fixes the reason for the races and inconsistencies by moving the
work of maintaining the ptrace fields into ptrace_stop.

The inconsistency that results in some ptrace_stop points continuing
with a signal while others will not I have left alone as it appears to
be part of our userspace ABI, and changing that risks breaking
userspace.

Eric W. Biederman (2):
      ptrace: Move setting/clearing ptrace_message into ptrace_stop
      ptrace: Return the signal to continue with from ptrace_stop

 include/linux/ptrace.h      | 17 +++++++----------
 include/uapi/linux/ptrace.h |  2 +-
 kernel/signal.c             | 40 ++++++++++++++++++++++++----------------
 3 files changed, 32 insertions(+), 27 deletions(-)

Eric