linux-kernel - Re: [PATCH 2/2] mm: zswap: remove unnecessary tree cleanups in zswap

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Message-ID: <CAF8kJuN25avTEgNTXdoz7N9eRuNTCdtGLA_kCuKB=_TRYT48cA@mail.gmail.com>
Date: Thu, 25 Jan 2024 17:09:43 -0800
From: Chris Li <chrisl@...nel.org>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Johannes Weiner <hannes@...xchg.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Nhat Pham <nphamcs@...il.com>, Chengming Zhou <zhouchengming@...edance.com>, 
	Huang Ying <ying.huang@...el.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: zswap: remove unnecessary tree cleanups in zswap_swapoff()

Hi Yosry,

On Thu, Jan 25, 2024 at 2:34 PM Yosry Ahmed <yosryahmed@...gle.com> wrote:
>
> > > problem is that after the entry is isolated from the zswap LRU, we
> > > need to grab the tree lock to make sure it's still there and get a
> > > ref, and just trying to lock the tree may be a UAF if we race with
> > > swapoff.
> >
> > I feel it is very wrong to have the tree freed while having
> > outstanding entry allocationed from the tree pending.
> > I would want to avoid that situation if possible.
>
> This should be the case with Chengming's solution.

Thanks for confirming. Looking forward to Chenming's patch.

Chris