linux-kernel - Re: [PATCH] x86, kaslr: avoid setup

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Message-ID: <CAGXu5jLK-k4JZO4eZSasRuSSQxeru94U9whMPcgD6iin40VVTA@mail.gmail.com>
Date:	Wed, 1 Oct 2014 11:08:56 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Baoquan He <bhe@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>,
	Pavel Machek <pavel@....cz>
Subject: Re: [PATCH] x86, kaslr: avoid setup_data when picking location

On Wed, Oct 1, 2014 at 11:01 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 09/11/2014 09:19 AM, Kees Cook wrote:
>> --- a/arch/x86/boot/compressed/aslr.c
>> +++ b/arch/x86/boot/compressed/aslr.c
>> @@ -183,12 +183,27 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
>>  static bool mem_avoid_overlap(struct mem_vector *img)
>>  {
>>       int i;
>> +     struct setup_data *ptr;
>>
>>       for (i = 0; i < MEM_AVOID_MAX; i++) {
>>               if (mem_overlaps(img, &mem_avoid[i]))
>>                       return true;
>>       }
>>
>> +     /* Avoid all entries in the setup_data linked list. */
>> +     ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data;
>> +     while (ptr) {
>> +             struct mem_vector avoid;
>> +
>> +             avoid.start = (u64)ptr;
>> +             avoid.size = sizeof(*ptr) + ptr->len;
>> +
>> +             if (mem_overlaps(img, &avoid))
>> +                     return true;
>> +
>> +             ptr = (struct setup_data *)(unsigned long)ptr->next;
>> +     }
>> +
>>       return false;
>>  }
>>
>>
>
> The use of (u64) in the assignment to avoid.start gives a nuisance
> warning on 32 bits.

Ah, good catch! This should be (unsigned long), I think. Shall I send
a follow-up patch, or do you want to fix this directly?

-Kees

-- 
Kees Cook
Chrome OS Security
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