linux-kernel - Re: [PATCH 2/3] mm, debug, kasan: save and dump freeing stack trace for kasan

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Message-ID: <927156e7-1f1c-2b28-8bc6-12bbf00fb785@suse.cz>
Date:   Thu, 26 Sep 2019 11:27:45 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        Qian Cai <cai@....pw>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Walter Wu <walter-zh.wu@...iatek.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: Re: [PATCH 2/3] mm, debug, kasan: save and dump freeing stack trace
 for kasan

On 9/26/19 11:16 AM, Kirill A. Shutemov wrote:
> On Wed, Sep 25, 2019 at 04:30:51PM +0200, Vlastimil Babka wrote:
>> The commit 8974558f49a6 ("mm, page_owner, debug_pagealloc: save and dump
>> freeing stack trace") enhanced page_owner to also store freeing stack trace,
>> when debug_pagealloc is also enabled. KASAN would also like to do this [1] to
>> improve error reports to debug e.g. UAF issues. This patch therefore introduces
>> a helper config option PAGE_OWNER_FREE_STACK, which is enabled when PAGE_OWNER
>> and either of DEBUG_PAGEALLOC or KASAN is enabled. Boot-time, the free stack
>> saving is enabled when booting a KASAN kernel with page_owner=on, or non-KASAN
>> kernel with debug_pagealloc=on and page_owner=on.
> 
> I would like to have an option to enable free stack for any PAGE_OWNER
> user at boot-time.
> 
> Maybe drop CONFIG_PAGE_OWNER_FREE_STACK completely and add
> page_owner_free=on cmdline option as yet another way to trigger
> 'static_branch_enable(&page_owner_free_stack)'?

Well, if you think it's useful, I'm not opposed.