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

From: Jan Beulich
Date: Thu Dec 14 2017 - 09:15:45 EST


>>> On 14.12.17 at 15:04, <jgross@xxxxxxxx> 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@xxxxxxxx>

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.

Jan