linux-kernel - Re: [PATCH] mm: cleancache: fix potential race in cleancache apis

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YNxVAZDttnWncNUy@casper.infradead.org>
Date:   Wed, 30 Jun 2021 12:26:57 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Cc:     권오훈 <ohoono.kwon@...sung.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
        "ohkwon1043@...il.com" <ohkwon1043@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: cleancache: fix potential race in cleancache apis

On Wed, Jun 30, 2021 at 10:13:28AM +0200, gregkh@...uxfoundation.org wrote:
> On Wed, Jun 30, 2021 at 04:33:10PM +0900, 권오훈 wrote:
> > Current cleancache api implementation has potential race as follows,
> > which might lead to corruption in filesystems using cleancache.
> > 
> > thread 0                thread 1                        thread 2
> > 
> >                         in put_page
> >                         get pool_id K for fs1
> > invalidate_fs on fs1
> > frees pool_id K
> >                                                         init_fs for fs2
> >                                                         allocates pool_id K
> >                         put_page puts page
> >                         which belongs to fs1
> >                         into cleancache pool for fs2
> > 
> > At this point, a file cache which originally belongs to fs1 might be
> > copied back to cleancache pool of fs2, which might be later used as if
> > it were normal cleancache of fs2, and could eventually corrupt fs2 when
> > flushed back.
> > 
> > Add rwlock in order to synchronize invalidate_fs with other cleancache
> > operations.
> > 
> > In normal situations where filesystems are not frequently mounted or
> > unmounted, there will be little performance impact since
> > read_lock/read_unlock apis are used.
> > 
> > Signed-off-by: Ohhoon Kwon <ohoono.kwon@...sung.com>
> 
> What commit does this fix?  Should it go to stable kernels?

I have a commit I haven't submitted yet with this changelog:

    Remove cleancache

    The last cleancache backend was deleted in v5.3 ("xen: remove tmem
    driver"), so it has been unused since.  Remove all its filesystem hooks.

    Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>