linux-kernel - Re: [PATCH 02/16] user_ns: use new hashtable implementation

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] [day] [month] [year] [list]

Message-ID: <877gsvzvqw.fsf@xmission.com>
Date:	Sat, 18 Aug 2012 15:21:59 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 02/16] user_ns: use new hashtable implementation

Sasha Levin <levinsasha928@...il.com> writes:

> On 08/15/2012 01:52 AM, Eric W. Biederman wrote:
>> Sasha Levin <levinsasha928@...il.com> writes:
>>> > Switch user_ns to use the new hashtable implementation. This reduces the amount of
>>> > generic unrelated code in user_ns.
>> Two concerns here.
>> 1) When adding a new entry you recompute the hash where previously that
>>    was not done.  I believe that will slow down adding of new entries.
>
> Since the hashtable doesn't expose the internal hashing to the user of the
> hashtable it would require adding a new interface to deal with in.
>
> I don't feel that a whole new interface to optimize out something which is very
> cheap (one multiplication + shift) in this case, I'd rather avoid having a new
> interface.
>
> Is it ok with you if I leave it as is in the next version of the
> patch?

No problem.  I was largely reviewing for potential gotchas, and things
that make me go hmm.

I don't think setuid is called enough for the hash table to be much of
a hotpath.  Although I haven't profiled it.

Eric

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/