linux-kernel - Re: [linux-next:master] [mm,page_owner] 4bedfb314b: BUG:KASAN:null-ptr-deref_in_init_page

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Message-ID: <ZegZCaFJrnAWL4kb@localhost.localdomain>
Date: Wed, 6 Mar 2024 08:19:37 +0100
From: Oscar Salvador <osalvador@...e.de>
To: Marco Elver <elver@...gle.com>
Cc: kernel test robot <oliver.sang@...el.com>, oe-lkp@...ts.linux.dev,
	lkp@...el.com, Linux Memory Management List <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: [linux-next:master] [mm,page_owner] 4bedfb314b:
 BUG:KASAN:null-ptr-deref_in_init_page_owner

On Tue, Mar 05, 2024 at 07:38:42PM +0100, Oscar Salvador wrote:
> But they point out to 
> 
> commit 4bedfb314bdd85c1662ecc46fa25b33b998f994d (HEAD, bisection)
> Author: Oscar Salvador <osalvador@...e.de>
> Date:   Thu Feb 15 22:59:03 2024 +0100
> 
>     mm,page_owner: maintain own list of stack_records structs
> 
> which the only thing it does is to retrieve the stack_record for
> {dummy,failure}.handle and increment their refcount and link them.
> I am pretty sure the problem comes from either dummy_handle or
> failure_handle being 0 and the stack_record we get is NULL.

Yes, jfyi: I "artificially" reproduced this by making
dummy_handle explicitly = 0 again.
And I see that KASAN points to the same location.

I am kind of surprised stackdepot ran out of space that early, but I
guess we cannot take anything for granted.

I am alrady working on a fixup to now blow up here.


-- 
Oscar Salvador
SUSE Labs