linux-kernel - Re: [PATCH v2 06/13] fork: Add generic vmalloced stack support

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Message-ID: <CALCETrWABPx5xysNnfX7H7yKFptDT7ys-P_3Kew4gZQQGLh-fw@mail.gmail.com>
Date:	Fri, 17 Jun 2016 15:18:52 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jann Horn <jann@...jh.net>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH v2 06/13] fork: Add generic vmalloced stack support

On Fri, Jun 17, 2016 at 1:57 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> On Fri, Jun 17, 2016 at 01:00:42PM -0700, Andy Lutomirski wrote:
>> @@ -213,24 +232,46 @@ struct kmem_cache *vm_area_cachep;
>>  /* SLAB cache for mm_struct structures (tsk->mm) */
>>  static struct kmem_cache *mm_cachep;
>>
>> -static void account_kernel_stack(struct thread_info *ti, int account)
>> +static void account_kernel_stack(struct task_struct *tsk, int account)
>>  {
>> -     struct zone *zone = page_zone(virt_to_page(ti));
>> +     struct zone *zone;
>> +     struct thread_info *ti = task_thread_info(tsk);
>> +     struct vm_struct *vm = task_stack_vm_area(tsk);
>> +
>> +     BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
>> +
>> +     if (vm) {
>> +             int i;
>>
>> -     mod_zone_page_state(zone, NR_KERNEL_STACK_KB,
>> -                         THREAD_SIZE / 1024 * account);
>> +             BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
>>
>> -     /* All stack pages belong to the same memcg. */
>> -     memcg_kmem_update_page_stat(
>> -             virt_to_page(ti), MEMCG_KERNEL_STACK,
>> -             account * (THREAD_SIZE / PAGE_SIZE));
>> +             for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
>> +                     mod_zone_page_state(page_zone(vm->pages[i]),
>> +                                         1, PAGE_SIZE / 1024 * account);
>
> Shouldn't the second argument be NR_KERNEL_STACK_KB instead of 1?

Indeed. Queued for v3.

--Andy