linux-kernel - Re: [PATCH 1/2] x86: consider effective protection attributes in W+X check

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Date:   Thu, 14 Dec 2017 15:21:39 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <JBeulich@...e.com>
Cc:     mingo@...e.hu, Thomas Gleixner <tglx@...utronix.de>,
        xen-devel <xen-devel@...ts.xenproject.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        sds@...ho.nsa.gov, linux-kernel@...r.kernel.org, hpa@...or.com
Subject: Re: [PATCH 1/2] x86: consider effective protection attributes in W+X
 check

On 14/12/17 15:15, Jan Beulich wrote:
>>>> On 14.12.17 at 15:04, <jgross@...e.com> wrote:
>> On 12/12/17 11:31, Jan Beulich wrote:
>>> @@ -335,42 +346,45 @@ static inline bool kasan_page_table(stru
>>>  
>>>  #if PTRS_PER_PMD > 1
>>>  
>>> -static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr, unsigned long P)
>>> +static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr,
>>> +			   pgprotval_t eff_in, unsigned long P)
>>>  {
>>>  	int i;
>>>  	pmd_t *start, *pmd_start;
>>> -	pgprotval_t prot;
>>> +	pgprotval_t prot, eff;
>>>  
>>>  	pmd_start = start = (pmd_t *)pud_page_vaddr(addr);
>>>  	for (i = 0; i < PTRS_PER_PMD; i++) {
>>>  		st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
>>>  		if (!pmd_none(*start)) {
>>> +			prot = pmd_flags(*start);
>>> +			eff = effective_prot(eff_in, prot);
>>>  			if (pmd_large(*start) || !pmd_present(*start)) {
>>> -				prot = pmd_flags(*start);
>>> -				note_page(m, st, __pgprot(prot), 4);
>>> +				note_page(m, st, __pgprot(prot), eff, 4);
>>>  			} else if (!kasan_page_table(m, st, pmd_start)) {
>>> -				walk_pte_level(m, st, *start,
>>> +				walk_pte_level(m, st, *start, eff,
>>>  					       P + i * PMD_LEVEL_MULT);
>>>  			}
>>
>> You can drop the braces for both cases. Applies to similar
>> constructs below, too.
> 
> I did consider that, but decided against to allow the patch to show
> more clearly what it is that is actually being changed.
> 
>> With that fixed you can add my:
>>
>> Reviewed-by: Juergen Gross <jgross@...e.com>
> 
> Thanks. I'd like to wait for the x86 maintainer's opinion, and hence
> won't add your R-b unless you tell me that's fine either way, or
> unless they too would prefer resulting code cleanliness over patch
> readability.

I'm fine with the braces kept, too.


Juergen