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From:   "Eric W. Biederman" <ebiederm@xmission.com>
To:     Kees Cook <keescook@chromium.org>
Cc:     linux-kernel@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Jens Axboe <axboe@kernel.dk>
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Date:   Fri, 18 Mar 2022 09:44:30 -0500
In-Reply-To: <202203171209.FC87C7B08@keescook> (Kees Cook's message of "Thu,
        17 Mar 2022 12:10:16 -0700")
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Subject: Re: [PATCH 1/2] ptrace: Move setting/clearing ptrace_message into
 ptrace_stop
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Kees Cook <keescook@chromium.org> writes:

> On Tue, Mar 15, 2022 at 06:21:08PM -0500, Eric W. Biederman wrote:
>> 
>> Today ptrace_message is easy to overlook as it not a core part of
>> ptrace_stop.  It has been overlooked so much that there are places
>> that set ptrace_message and don't clear it, and places that never set
>> it.  So if you get an unlucky sequence of events the ptracer may be
>> able to read a ptrace_message that does not apply to the current
>> ptrace stop.
>> 
>> Move setting of ptrace_message into ptrace_stop so that it always gets
>> set before the stop, and always gets cleared after the stop.  This
>> prevents non-sense from being reported to userspace and makes
>> ptrace_message more visible in the ptrace helper functions so that
>> kernel developers can see it.
>> 
>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
>
> This looks good to me. Did you happen to run the seccomp selftests
> before/after these changes?

I did not.  This is a pure ptrace change.  Do you see a way that seccomp
could be involved?

Eric