linux-kernel - Re: [PATCH v3] Make PTRACE_SEIZE set ptrace options specified in 'data'

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Date:	Sun, 11 Sep 2011 08:34:31 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	Denys Vlasenko <vda.linux@...glemail.com>
Subject: Re: [PATCH v3] Make PTRACE_SEIZE set ptrace options specified in
 'data'

On Thu, Sep 08, 2011 at 08:22:04PM +0200, Denys Vlasenko wrote:
> Make PTRACE_SEIZE set ptrace options specified in 'data' parameter
>     
> This can be used to close a few corner cases in strace where we get
> unwanted racy behavior after attach, but before we have a chance
> to set options (the notorious post-execve SIGTRAP comes to mind),
> and removes the need to track "did we set opts for this task" state
> in strace internals.
>     
> While we are at it:
>     
> Make it possible to extend SEIZE in the future with more functionality
> by passing non-zero 'addr' parameter.
> To that end, error out if 'addr' is non-zero.
> PTRACE_ATTACH did not (and still does not) have such check,
> and users (strace) do pass garbage there... let's avoid repeating
> this mistake with SEIZE.
>     
> Set all task->ptrace bits in one operation - before this change,
> we were adding PT_SEIZED and PT_PTRACE_CAP with task->ptrace |= BIT ops.
> This was probably ok (not a bug), but let's be on a safer side.
> 
> Changes since v2: use (unsigned long) casts instead of (long) ones,
> move PTRACE_SEIZE_DEVEL-related code to separate lines of code.
> 
>     
> Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>

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

Thanks.

-- 
tejun
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