linux-kernel - Re: [PATCH] kthreads: kill CLONE_KERNEL, change kernel_thread(kernel_init) to avoid CLONE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140414110504.GH11096@twins.programming.kicks-ass.net>
Date:	Mon, 14 Apr 2014 13:05:04 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kthreads: kill CLONE_KERNEL, change
 kernel_thread(kernel_init) to avoid CLONE_SIGHAND

On Sun, Apr 13, 2014 at 09:56:17PM +0200, Oleg Nesterov wrote:
> 1. Remove CLONE_KERNEL, it has no users and it is dangerous.
> 
>    The (old) comment says "List of flags we want to share for kernel
>    threads" but this is not true, we do not want to share ->sighand by
>    default. This flag can only be used if the caller is sure that both
>    parent/child will never play with signals (say, allow_signal/etc).
> 
> 2. Change rest_init() to clone kernel_init() without CLONE_SIGHAND.
> 
>    In this case CLONE_SIGHAND does not really hurt, and it looks like
>    optimization because copy_sighand() can avoid kmem_cache_alloc().
> 
>    But in fact this only adds the minor pessimization. kernel_init()
>    is going to exec the init process, and de_thread() will need to
>    unshare ->sighand and do kmem_cache_alloc(sighand_cachep) anyway,
>    but it needs to do more work and take tasklist_lock and siglock.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Seems good;

Acked-by: Peter Zijlstra <peterz@...radead.org>

I'm thinking the idea was for Andrew to pick this up?
--
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/