linux-kernel - Re: [PATCH v5 1/3] arm64: ptrace: reload a syscall number after ptrace operations

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Date:	Fri, 25 Jul 2014 12:03:42 +0100
From:	Will Deacon <will.deacon@....com>
To:	AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Deepak Saxena <dsaxena@...aro.org>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/3] arm64: ptrace: reload a syscall number after
 ptrace operations

On Fri, Jul 25, 2014 at 11:36:49AM +0100, AKASHI Takahiro wrote:
> On 07/25/2014 12:01 AM, Andy Lutomirski wrote:
> >>> If so, then you risk (at least) introducing
> >>>
> >>> a nice user-triggerable OOPS if audit is enabled.
> >>
> >>
> >> Can you please elaborate this?
> >> Since I didn't find any definition of audit's behavior when syscall is
> >> rewritten to -1, I thought it is reasonable to skip "exit tracing" of
> >> "skipped" syscall.
> >> (otherwise, "fake" seems to be more appropriate :)
> >
> > The audit entry hook will oops if you call it twice in a row without
> > calling the exit hook in between.
> 
> Thank you, I could reproduce this problem which hits BUG(in_syscall) in
> audit_syscall_entry(). Really bad, and I fixed it in my next version and
> now a "skipped" system call is also traced by audit.

Can you reproduce this on arch/arm/ too? If so, we should also fix the code
there.

Will
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