>>> On 26.02.18 at 11:47, <aryabinin@xxxxxxxxxxxxx> wrote:
>
> On 02/26/2018 01:08 PM, Jan Beulich wrote:
>>>>> 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.
>
> kasan_zero_p?? are used to map kasan_zero_page. That's it.
Ah, thanks for explaining.
>> 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.
>
> I'm not sure I understand what do you mean.
> If we somehow screw up and accidentally make kasan_zero_pte writable and executable,
> note_page() should report this. With your patch, it won't work.
If this is a case to care about, simply passing "prot" won't be right
though - the callers accumulated effective protections would then
need passing in here, and merging with prot.
Before I do this for a possible v4, I'd like to seek clarification
though whether this really is a case to care about.
Jan
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|