linux-kernel - Re: [PATCH 1/2] slab: __GFP_ZERO is incompatible with a constructor

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:   Tue, 10 Apr 2018 12:45:56 -0500 (CDT)
From:   Christopher Lameter <cl@...ux.com>
To:     Matthew Wilcox <willy@...radead.org>
cc:     Eric Dumazet <eric.dumazet@...il.com>, linux-mm@...ck.org,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/2] slab: __GFP_ZERO is incompatible with a
 constructor

On Tue, 10 Apr 2018, Matthew Wilcox wrote:

> > How do you envision dealing with the SLAB_TYPESAFE_BY_RCU slab caches?
> > Those must have a defined state of the objects at all times and a constructor is
> > required for that. And their use of RCU is required for numerous lockless
> > lookup algorithms in the kernhel.
>
> Not at all times.  Only once they've been used.  Re-constructing them
> once they've been used might break the rcu typesafety, I suppose ...
> would need to examine the callers.

Objects can be freed and reused and still be accessed from code that
thinks the object is the old and not the new object....