linux-kernel - Re: [PATCH 2/4] arch/arm: move secure

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Message-ID: <CAGXu5jLohAwgRFRrakFMYCRoSumY5NyW+bQ5=Wzq17b6xzpDNw@mail.gmail.com>
Date:	Thu, 1 Nov 2012 13:50:11 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, Will Deacon <will.deacon@....com>,
	Will Drewry <wad@...omium.org>,
	Geremy Condra <gcondra@...gle.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH 2/4] arch/arm: move secure_computing into trace

On Thu, Nov 1, 2012 at 1:33 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> It's pointless having:
>
>         tst     r10, #_TIF_SECCOMP
>         bne     __sys_trace
>         tst     r10, #_TIF_SYSCALL_WORK
>         bne     __sys_trace
>
> Instead, make TIF_SECCOMP be bit 11, combine it into _TIF_SYSCALL_WORK, and
> eliminate all of that CONFIG_SECCOMP block.

Ah! Good point; I'd missed that _WORK was a bit field. I'll make those changes.

>> diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
>> index 739db3a..6b0e14b 100644
>> --- a/arch/arm/kernel/ptrace.c
>> +++ b/arch/arm/kernel/ptrace.c
>> @@ -916,13 +916,15 @@ enum ptrace_syscall_dir {
>>       PTRACE_SYSCALL_EXIT,
>>  };
>>
>> -static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
>> -                             enum ptrace_syscall_dir dir)
>> +asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
>
> I'm not sure this change is correct (combined with your hunk below).
> What if we have auditing enabled but trace disabled?  How do we reach
> audit_syscall_entry()?  Or the tracehook stuff?
>
> This patch looks wrong in too many ways.

Oh, yeah, you're totally right. I will fix that up. Thanks!

-Kees

-- 
Kees Cook
Chrome OS Security
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