linux-kernel - Re: [PATCH v4 1/6] mm/zswap: change dstmem size to one page

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Message-ID: <CAKEwX=PDeez9D8t4WSe2qd753h=06ZSJwQ8TQDv1xLXB0cpn-Q@mail.gmail.com>
Date: Wed, 27 Dec 2023 15:21:45 -0800
From: Nhat Pham <nphamcs@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Chengming Zhou <zhouchengming@...edance.com>, Barry Song <21cnbao@...il.com>, 
	Seth Jennings <sjenning@...hat.com>, Johannes Weiner <hannes@...xchg.org>, 
	Vitaly Wool <vitaly.wool@...sulko.com>, Chris Li <chriscli@...gle.com>, 
	Yosry Ahmed <yosryahmed@...gle.com>, Dan Streetman <ddstreet@...e.org>, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, Chris Li <chrisl@...nel.org>
Subject: Re: [PATCH v4 1/6] mm/zswap: change dstmem size to one page

On Wed, Dec 27, 2023 at 12:58 PM Andrew Morton
<akpm@...ux-foundation.org> wrote:
>
> On Wed, 27 Dec 2023 14:11:06 +0800 Chengming Zhou <zhouchengming@...edance.com> wrote:
>
> > > i remember there was an over-compression case,  that means the compressed
> > > data can be bigger than the source data. the similar thing is also done in zram
> > > drivers/block/zram/zcomp.c
> >
> > Right, there is a buffer overflow report[1] that I just +to you.
>
> What does "[1]" refer to?  Is there a bug report about this series?

I think Chengming was referring to this:

https://lore.kernel.org/lkml/0000000000000b05cd060d6b5511@google.com/

Syzkaller/syzbot found an edge case where the page's "compressed" form
was larger than one page, which tripped up the compression code (since
we reduced the compression buffer size to 1 page here).