linux-kernel - Re: [PATCH 5/6] selinux: improve role transition hashing

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]

Date:   Fri, 8 Sep 2023 14:46:28 -0400
From:   Stephen Smalley <stephen.smalley.work@...il.com>
To:     Christian Göttsche <cgzones@...glemail.com>
Cc:     selinux@...r.kernel.org, Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] selinux: improve role transition hashing

On Fri, Aug 18, 2023 at 11:12 AM Christian Göttsche
<cgzones@...glemail.com> wrote:
>
> The number of buckets is calculated by performing a binary AND against
> the mask of the hash table, which is one less than its size (which is a
> power of two).  This leads to all top bits being discarded, e.g. with
> the Reference Policy on Debian there exists 376 entries, leading to a
> size of 512, discarding the top 23 bits.
>
> Use jhash to improve the hash table utilization:
>
>     # current
>     roletr:  376 entries and 124/512 buckets used, longest chain length 8, sum of chain length^2 1496
>
>     # patch
>     roletr:  376 entries and 266/512 buckets used, longest chain length 4, sum of chain length^2 646
>
> Signed-off-by: Christian Göttsche <cgzones@...glemail.com>

Reviewed-by: Stephen Smalley <stephen.smalley.work@...il.com>