linux-kernel - Re: [PATCH 2/5] x86, mpx: hook #BR exception handler to allocate bound tables

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Message-ID: <52D35ABB.8070904@intel.com>
Date:	Mon, 13 Jan 2014 11:17:15 +0800
From:	Ren Qiaowei <qiaowei.ren@...el.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] x86, mpx: hook #BR exception handler to allocate
 bound tables

On 01/12/2014 05:20 PM, Borislav Petkov wrote:
> On Sun, Jan 12, 2014 at 05:20:00PM +0800, Qiaowei Ren wrote:
>> +static bool allocate_bt(unsigned long bd_entry)
>> +{
>> +	unsigned long bt_size = 1UL << (MPX_L2_BITS+MPX_L2_SHIFT);
>> +	unsigned long bt_addr, old_val;
>> +
>> +	bt_addr = sys_mmap_pgoff(0, bt_size, PROT_READ | PROT_WRITE,
>> +			MAP_ANONYMOUS | MAP_PRIVATE | MAP_POPULATE, -1, 0);
>
> Are we sure about this? We can do a possible memory allocation in
> mmap_region() in this exception handler context. And yes, we do a
> conditional_sti(), which makes it all the more susceptible.
>
> Have you run this with lockdep enabled?
>
Yes, I run this with lockdep enabled.

Thanks,
Qiaowei
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