linux-kernel - Re: [PATCH 08/16] ptrace: Only populate last

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Message-ID: <20220524152725.GE14347@redhat.com>
Date:   Tue, 24 May 2022 17:27:25 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, rjw@...ysocki.net, mingo@...nel.org,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, mgorman@...e.de, bigeasy@...utronix.de,
        Will Deacon <will@...nel.org>, tj@...nel.org,
        linux-pm@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-xtensa@...ux-xtensa.org, Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, linux-ia64@...r.kernel.org,
        Robert OCallahan <roc@...nos.co>, Kyle Huey <khuey@...nos.co>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Douglas Miller <dougmill@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 08/16] ptrace: Only populate last_siginfo from ptrace

On 05/18, Eric W. Biederman wrote:
>
> The code in ptrace_signal to populate siginfo if the signal number
> changed is buggy.  If the tracer contined the tracee using
> ptrace_detach it is guaranteed to use the real_parent (or possibly a
> new tracer) but definitely not the origional tracer to populate si_pid
> and si_uid.

I guess nobody cares. As the comment says

	 If the debugger wanted something
	 specific in the siginfo structure then it should
	 have updated *info via PTRACE_SETSIGINFO.

otherwise I don't think si_pid/si_uid have any value.

However the patch looks fine to me, just the word "buggy" looks a bit
too strong imo.

Oleg.