linux-kernel - Re: [PATCH v2 2/3] mm: don't hide potentially null memmap pointer in sparse_remove_one

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Message-ID: <edac179f0626a6e0bd91922d876934abf1b9bb19.camel@d-silva.org>
Date:   Wed, 26 Jun 2019 16:30:55 +1000
From:   "Alastair D'Silva" <alastair@...ilva.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Baoquan He <bhe@...hat.com>, Qian Cai <cai@....pw>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 2/3] mm: don't hide potentially null memmap pointer
 in sparse_remove_one_section

On Wed, 2019-06-26 at 08:23 +0200, Michal Hocko wrote:
> On Wed 26-06-19 16:11:22, Alastair D'Silva wrote:
> > From: Alastair D'Silva <alastair@...ilva.org>
> > 
> > By adding offset to memmap before passing it in to
> > clear_hwpoisoned_pages,
> > we hide a potentially null memmap from the null check inside
> > clear_hwpoisoned_pages.
> > 
> > This patch passes the offset to clear_hwpoisoned_pages instead,
> > allowing
> > memmap to successfully peform it's null check.
> 
> Same issue with the changelog as the previous patch (missing WHY).
> 

The first paragraph explains what the problem is with the existing code
(same applies to 1/3 too).

-- 
Alastair D'Silva           mob: 0423 762 819
skype: alastair_dsilva    
Twitter: @EvilDeece
blog: http://alastair.d-silva.org