linux-kernel - Re: [PATCH] rxrpc_find_service_conn_rcu: use read_seqbegin() rather than read_seqbegin_or

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: <20231101223824.GG32034@redhat.com>
Date:   Wed, 1 Nov 2023 23:38:24 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     David Howells <dhowells@...hat.com>
Cc:     Marc Dionne <marc.dionne@...istor.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        linux-afs@...ts.infradead.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rxrpc_find_service_conn_rcu: use read_seqbegin() rather
 than read_seqbegin_or_lock()

On 11/01, David Howells wrote:
>
> Oleg Nesterov <oleg@...hat.com> wrote:
>
> > Just none of read_seqbegin_or_lock/need_seqretry/done_seqretry
> > helpers make any sense in this code.
>
> I disagree.  I think in at least a couple of cases I do want a locked second
> path

Sorry for confusion. I never said that the 2nd locked pass makes no sense.

My only point is that rxrpc_find_service_conn_rcu() (and more) use
read_seqbegin_or_lock() incorrectly. They can use read_seqbegin() and this
won't change the current behaviour.

So lets change these users first? Then we can discuss the possible changes
in include/linux/seqlock.h and (perhaps) update the users which actually
want the locking on the 2nd pass.

Oleg.