Subject: Re: [PATCH 1/2] mm/kasan: dump alloc/free stack for page allocator

From: Walter Wu <[email-masked]>
Date: Wed, 4 Sep 2019 22:06:05 +0800

On Wed, 2019-09-04 at 14:49 +0200, Vlastimil Babka wrote:
> On 9/4/19 8:51 AM, Walter Wu wrote:
> > This patch is KASAN report adds the alloc/free stacks for page allocator
> > in order to help programmer to see memory corruption caused by page.
> > 
> > By default, KASAN doesn't record alloc/free stack for page allocator.
> > It is difficult to fix up page use-after-free issue.
> > 
> > This feature depends on page owner to record the last stack of pages.
> > It is very helpful for solving the page use-after-free or out-of-bound.
> > 
> > KASAN report will show the last stack of page, it may be:
> > a) If page is in-use state, then it prints alloc stack.
> >    It is useful to fix up page out-of-bound issue.
> 
> I expect this will conflict both in syntax and semantics with my series [1] that
> adds the freeing stack to page_owner when used together with debug_pagealloc,
> and it's now in mmotm. Glad others see the need as well :) Perhaps you could
> review the series, see if it fulfils your usecase (AFAICS the series should be a
> superset, by storing both stacks at once), and perhaps either make KASAN enable
> debug_pagealloc, or turn KASAN into an alternative enabler of the functionality
> there?
> 
> Thanks, Vlastimil
> 
> [1] https://lore.kernel.org/linux-mm/[email-masked]/t/#u
> 
Thanks your information.
We focus on the smartphone, so it doesn't enable
CONFIG_TRANSPARENT_HUGEPAGE, Is it invalid for our usecase?
And It looks like something is different, because we only need last
stack of page, so it can decrease memory overhead.
I will try to enable debug_pagealloc(with your patch) and KASAN, then we
see the result.

Thanks.
Walter 

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