linux-kernel - Re: [PATCH] arm: ptrace: fix syscall modification under PTRACE_O

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Message-ID: <20140623084608.GA9316@arm.com>
Date:	Mon, 23 Jun 2014 09:46:09 +0100
From:	Will Deacon <will.deacon@....com>
To:	Kees Cook <keescook@...omium.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	Andy Lutomirski <luto@...capital.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Austin <Jonathan.Austin@....com>,
	André Hentschel <nerv@...ncrow.de>,
	Oleg Nesterov <oleg@...hat.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Ricky Zhou <rickyz@...gle.com>
Subject: Re: [PATCH] arm: ptrace: fix syscall modification under
 PTRACE_O_TRACESECCOMP

On Fri, Jun 20, 2014 at 07:10:46PM +0100, Kees Cook wrote:
> On Fri, Jun 20, 2014 at 10:36 AM, Kees Cook <keescook@...omium.org> wrote:
> > On Fri, Jun 20, 2014 at 10:23 AM, Will Deacon <will.deacon@....com> wrote:
> >> Right, gotcha. Thanks for the explanation. I was confused, because
> >> tracehook_report_syscall does the right thing (returns
> >> current_thread_info()->syscall), but if we don't have TIF_SYSCALL_TRACE set,
> >> then updates during the secure_computing callback will be ignored.
> >>
> >> However, my fix to this is significantly smaller than your patch, so I fear
> >> I'm still missing something.
> >
> > Oh, yes, that's much smaller. Nice! I will test this and report back.
> 
> Yup, I can confirm this works. Thanks!
> 
> Tested-by: Kees Cook <keescook@...omium.org>

Thanks, Kees. I'll post a patch shortly. I'll try and remember to keep an
eye out for this when seccomp lands for arm64 too.

Will
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