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Date: Wed, 5 Aug 2015 10:00:37 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Willy Tarreau <w@1wt.eu>
Cc: Andy Lutomirski <luto@kernel.org>, Kees Cook <keescook@chromium.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        "security@kernel.org" <security@kernel.org>, X86 ML <x86@kernel.org>,
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        LKML <linux-kernel@vger.kernel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        Jan Beulich <jbeulich@suse.com>, xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH v3 1/1] x86: allow to enable/disable modify_ldt at run
 time
Message-ID: <20150805080037.GA14472@gmail.com>
References: <1438626217-23970-1-git-send-email-w@1wt.eu>
 <20150804084911.GA24204@1wt.eu>
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* Willy Tarreau <w@1wt.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