linux-kernel - Re: [PATCH] mm: workingset: fix NULL ptr dereference

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Message-ID: <20180410123857.GJ21835@dhcp22.suse.cz>
Date:   Tue, 10 Apr 2018 14:38:57 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Minchan Kim <minchan@...nel.org>, Chao Yu <yuchao0@...wei.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Christopher Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz>,
        Chris Fries <cfries@...gle.com>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] mm: workingset: fix NULL ptr dereference

On Tue 10-04-18 04:56:51, Matthew Wilcox wrote:
> On Tue, Apr 10, 2018 at 11:59:03AM +0900, Minchan Kim wrote:
> > Okay, I hope this version clear current concerns.
> 
> It doesn't.  The right place to warn about GFP_ZERO used with a
> constructor is _slab_, like the patch I already sent.  We have no idea
> what other places might have the same bug, and slab is the only place
> to catch that.

I agree with that. Radix tree shouldn't be really that special. I would
rather get rid of the ctor subtle thingy but if we absolutely have to
keep it then the GFP_RECLAIM_MASK filtering and a warning in slab for
__GFP_ZERO looks like a reasonable step forward.
-- 
Michal Hocko
SUSE Labs