linux-kernel - Re: [PATCH 1/2] ptrace: don't modify flags on PTRACE

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Date:	Sun, 11 Sep 2011 08:32:29 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	dvlasenk@...hat.com, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 1/2] ptrace: don't modify flags on PTRACE_SETOPTIONS
 failure

On Fri, Sep 09, 2011 at 08:24:37AM +0200, Denys Vlasenko wrote:
> ptrace: don't modify flags on PTRACE_SETOPTIONS failure
> 
> On ptrace(PTRACE_SETOPTIONS, pid, 0, <opts>), we used to set
> those option bits which are known, and then fail with -EINVAL
> if there are some unknown bits in <opts>.
> 
> This in inconsistent with typical error handling, which
> does not change any state if input is invalid.
> 
> This patch changes PTRACE_SETOPTIONS behavior so that
> in this case, we return -EINVAL and don't change any bits
> in task->ptrace.
> 
> It's very unlikely that there is userspace code in the wild which
> will be affected by this change: it should have the form
> 
>     ptrace(PTRACE_SETOPTIONS, pid, 0, PTRACE_O_BOGUSOPT)
> 
> where PTRACE_O_BOGUSOPT is a constant unknown to the kernel.
> But kernel headers, naturally, don't contain any
> PTRACE_O_BOGUSOPTs, thus the only way userspace can use one
> if it defines one itself. I can't see why anyone would do such
> a thing deliberately.
> 
> Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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