Re: [tip:x86/mm] x86/mm: Consider effective protection attributes in W+X check

[Jan Beulich]

>>> On 26.02.18 at 11:00, <aryabinin@xxxxxxxxxxxxx> wrote:
> On 02/26/2018 11:48 AM, tip-bot for Jan Beulich wrote:
>> @@ -351,7 +362,7 @@ static inline bool kasan_page_table(struct seq_file *m, struct pg_state *st,
>>  	    (pgtable_l5_enabled && __pa(pt) == __pa(kasan_zero_p4d)) ||
>>  	    __pa(pt) == __pa(kasan_zero_pud)) {
>>  		pgprotval_t prot = pte_flags(kasan_zero_pte[0]);
>> -		note_page(m, st, __pgprot(prot), 5);
>> +		note_page(m, st, __pgprot(prot), 0, 5);
> 
> Isn't this disables W+X check for kasan page table?
> Methinks it should be 'prot' here.

Might well be - I actually did ask the question before sending v3,
but didn't get any answer (yet). The kasan_zero_p?d names
suggested to me that this is a shortcut for mappings which
otherwise would be non-present anyway, but that was merely a
guess. As to W+X checks - I can't see how the result could be
any better if the protections of kasan_zero_pte[0] would be
used: Those can't possibly be applicable independent of VA.

Jan