linux-kernel - Re: [PATCH v6 2/6] arm64: ptrace: allow tracer to skip a system call

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Date:	Mon, 1 Sep 2014 12:47:51 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:	Will Deacon <will.deacon@....com>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Kees Cook <keescook@...omium.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"arndb@...db.de" <arndb@...db.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Deepak Saxena <dsaxena@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 2/6] arm64: ptrace: allow tracer to skip a system
	call

On Wed, Aug 27, 2014 at 02:55:46PM +0900, AKASHI Takahiro wrote:
> 1)
> setting x0 to -ENOSYS is necessary because, otherwise, user-issued syscall(-1) will
> return a bogus value when audit tracing is on.
>
> Please note that, on arm,
>                  not traced      traced
>                  ------          ------
> syscall(-1)      aborted         OOPs(BUG_ON)
> syscall(-3000)   aborted         aborted
> syscall(1000)    ENOSYS          ENOSYS

Two points here:

1. You've found a case which causes a BUG_ON().  Where is the bug report
   for this, so the problem can be investigated and resolved?

2. What do you mean by "aborted" ?

Please, if you find a problem with 32-bit ARM, report it.  Don't hide it,
because hiding it can be a security issue or in the case of BUG_ON(), it
could be a denial of service issue.

As you're part of Linaro, I would have thought you'd be more responsible
in this regard - after all, Linaro is supposed to be about improving the
ARM kernel...  Maybe I got that wrong, and Linaro is actually about
ensuring that the ARM kernel is stuffed full of broken features?

-- 
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