linux-kernel - Re: [PATCH] fs/exec.c: Add fast path for ENOENT on PATH search before allocating mm

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]

Message-ID: <202311071445.53E5D72C@keescook>
Date:   Tue, 7 Nov 2023 14:50:01 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Mateusz Guzik <mjguzik@...il.com>
Cc:     Josh Triplett <josh@...htriplett.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Alexander Viro <viro@...iv.linux.org.uk>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/exec.c: Add fast path for ENOENT on PATH search
 before allocating mm

On Tue, Nov 07, 2023 at 10:23:16PM +0100, Mateusz Guzik wrote:
> If the patch which dodges second lookup still somehow appears slower a
> flamegraph or other profile would be nice. I can volunteer to take a
> look at what's going on provided above measurements will be done and
> show funkyness.

When I looked at this last, it seemed like all the work done in
do_filp_open() (my patch, which moved the lookup earlier) was heavier
than the duplicate filename_lookup().

What I didn't test was moving the sched_exec() before the mm creation,
which Peter confirmed shouldn't be a problem, but I think that might be
only a tiny benefit, if at all.

If you can do some comparisons, that would be great; it always takes me
a fair bit of time to get set up for flame graph generation, etc. :)

-Kees

-- 
Kees Cook