linux-kernel - Re: [PATCH] mm/slub: fix a deadlock in shuffle

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: <1568642487.5576.152.camel@lca.pw>
Date:   Mon, 16 Sep 2019 10:01:27 -0400
From:   Qian Cai <cai@....pw>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        peterz@...radead.org, mingo@...hat.com
Cc:     akpm@...ux-foundation.org, tglx@...utronix.de, thgarnie@...gle.com,
        tytso@....edu, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, will@...nel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, keescook@...omium.org
Subject: Re: [PATCH] mm/slub: fix a deadlock in shuffle_freelist()

On Mon, 2019-09-16 at 11:03 +0200, Sebastian Andrzej Siewior wrote:
> On 2019-09-13 12:27:44 [-0400], Qian Cai wrote:
> …
> > Chain exists of:
> >   random_write_wait.lock --> &rq->lock --> batched_entropy_u32.lock
> > 
> >  Possible unsafe locking scenario:
> > 
> >        CPU0                    CPU1
> >        ----                    ----
> >   lock(batched_entropy_u32.lock);
> >                                lock(&rq->lock);
> >                                lock(batched_entropy_u32.lock);
> >   lock(random_write_wait.lock);
> 
> would this deadlock still occur if lockdep knew that
> batched_entropy_u32.lock on CPU0 could be acquired at the same time
> as CPU1 acquired its batched_entropy_u32.lock?

I suppose that might fix it too if it can teach the lockdep the trick, but it
would be better if there is a patch if you have something in mind that could be
tested to make sure.