linux-kernel - Re: [PATCH v3 1/1] x86: allow to enable/disable modify

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Message-ID: <20150805080037.GA14472@gmail.com>
Date:	Wed, 5 Aug 2015 10:00:37 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Willy Tarreau <w@....eu>
Cc:	Andy Lutomirski <luto@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"security@...nel.org" <security@...nel.org>,
	X86 ML <x86@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Sasha Levin <sasha.levin@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Jan Beulich <jbeulich@...e.com>,
	xen-devel <xen-devel@...ts.xen.org>
Subject: Re: [PATCH v3 1/1] x86: allow to enable/disable modify_ldt at run
 time


* Willy Tarreau <w@....eu> wrote:

> @@ -276,6 +282,15 @@ asmlinkage int sys_modify_ldt(int func, void __user *ptr,
>  {
>  	int ret = -ENOSYS;
>  
> +	if (!sysctl_modify_ldt) {
> +		printk_ratelimited(KERN_INFO
> +			"Denied a call to modify_ldt() from %s[%d] (uid: %d)."
> +			" Adjust sysctl if this was not an exploit attempt.\n",
> +			current->comm, task_pid_nr(current),
> +			from_kuid_munged(current_user_ns(), current_uid()));

UI nit: so this message should really tell the user _which_ sysctl to configure, 
instead of passive-aggressively alluding to the fact that there's a sysctl 
somewhere that might do the trick...

Thanks,

	Ingo
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