[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <54098BA1.3090508@linaro.org>
Date: Fri, 05 Sep 2014 19:08:33 +0900
From: AKASHI Takahiro <takahiro.akashi@...aro.org>
To: Russell King - ARM Linux <linux@....linux.org.uk>
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 09/02/2014 06:16 PM, Russell King - ARM Linux wrote:
> On Tue, Sep 02, 2014 at 05:47:29PM +0900, AKASHI Takahiro wrote:
>> On 09/01/2014 08:47 PM, Russell King - ARM Linux wrote:
>>> 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?
>>
>> I think that I mentioned it could also happen on arm somewhere in a talk
>> with Will, but don't remember exactly when.
>
> Sorry, not good enough. Please report this bug so it can be investigated
> and fixed.
Please review my patch as well as the commit message.
>>> 2. What do you mean by "aborted" ?
>>
>> I mean that the process will receive SIGILL and get aborted.
>> A system call number, like -1 and -3000, won't be trapped by *switch*
>> statement in asm_syscall() and end up with being signaled.
>
> That is correct behaviour - because numbers greater than 0xf0000 (or
> 0x9f0000 for OABI - the 0x900000 offset on the syscalls on OABI is to
> distinguish them from syscalls used by RISC OS) are not intended to
> be Linux syscalls per-se.
I tried to make such invalid/pseudo syscalls hehave in the same way
whether or not a task is traced (by seccomp, ptrace or audit).
>>> 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?
>>
>> I thought my first priority was on arm64 (and then arm), but now that
>> you and Will seem to want to see the fix first on arm, okey, I will
>> start with arm issue.
>
> So what you're saying there is that if you find a bug in ARM code, which
> everyone is currently using, you can ignore it until you've sorted out
> ARM64 which almost no one is using.
>
> This is absurd, and whoever has set your priorities is clearly on drugs.
Thank you. I learned a new English word, absurd.
-Takahiro AKASHI
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists