linux-kernel - Optimising USERNS mapping translation.

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-next>] [day] [month] [year] [list]

Date:	Tue, 15 Sep 2015 22:35:45 +1000
From:	Aleksa Sarai <cyphar@...har.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andy Lutomirski <luto@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Lameter <cl@...ux.com>,
	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Subject: Optimising USERNS mapping translation.

Hi,

I'm wondering if there's a reason that we do a linear search for the
mapping translations between kuid_t and uid_t. Surely something like a
radix trie would (potentially) allow for better storage and lookup? Is
the whole "an extent fits in a cache line" a good enough optimisation
that it would be pointless to use a better structure? Also, is there a
good reason why we have UID_GID_MAP_MAX_EXTENTS = 5 (other than the
one cache line thing)? Surely it's not more efficient to have to
create a bunch of nested namespaces in order to have more than 5
extents?

-- 
Aleksa Sarai (cyphar)
www.cyphar.com
--
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/