linux-kernel - Re: [PATCH] Fix data race in mark_rt_mutex

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 for Android: free password hash cracker in your pocket

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

Date:   Mon, 23 Jan 2023 12:34:37 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Hernan Ponce de Leon <hernan.poncedeleon@...weicloud.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        longman@...hat.com, boqun.feng@...il.com, akpm@...l.org,
        tglx@...utronix.de, joel@...lfernandes.org,
        diogo.behrens@...wei.com, jonas.oberhauser@...wei.com,
        linux-kernel@...r.kernel.org,
        Hernan Ponce de Leon <hernanl.leon@...wei.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH] Fix data race in mark_rt_mutex_waiters

On Mon, Jan 23, 2023 at 08:40:14AM -0800, Paul E. McKenney wrote:
> In the case, the value read is passed into cmpxchg_relaxed(), which
> checks the value against memory.  In this case, as Arjan noted, the only
> compiler-and-silicon difference between data_race() and READ_ONCE()
> is that use of data_race() might allow the compiler to do things like
> tear the load, thus forcing the occasional spurious cmpxchg_relaxed()
> failure.

Is it possible in theory for a torn load to cause a spurious 
cmpxchg_relaxed() success?  Or would that not matter here?

Alan