linux-kernel - Re: [PATCH 3/4] cgroup: Use __counted

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: <ecrvq2zi3tyewmjis6wdwxsvzkosobzowrm4xoxzxq35hhobev@m6kroxwbnfa7>
Date: Thu, 18 Dec 2025 17:32:35 +0100
From: Michal Koutný <mkoutny@...e.com>
To: Tejun Heo <tj@...nel.org>, 
	"Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc: Chen Ridong <chenridong@...weicloud.com>, cgroups@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
	Johannes Weiner <hannes@...xchg.org>, Kees Cook <kees@...nel.org>, 
	"Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: Re: [PATCH 3/4] cgroup: Use __counted_by for cgroup::ancestors

On Thu, Dec 18, 2025 at 06:09:42AM -1000, Tejun Heo <tj@...nel.org> wrote:
> On Thu, Dec 18, 2025 at 03:09:32PM +0800, Chen Ridong wrote:
> > Note that this level may already be used in existing BPF programs (e.g.,
> > tools/testing/selftests/bpf/progs/task_ls_uptr.c). Do we need to consider compatibility here?
> 
> That's a good point.

I wouldn't be concerned about this particular aspect. The commit
e6ac2450d6dee ("bpf: Support bpf program calling kernel function")
excludes ABIs, the example program uses ksyms (not kfuncs), so there
could even apply Documentation/process/stable-api-nonsense.rst.
OTOH, the semantics of level is unchanged for BPF helpers (that are the
official API).

> Is __counted_by instrumentation tied to some compiler flag? If so,
> might as well make it an optional extra field specifically for the
> annotation rather than changing the meaning of an existing field.

Honestly, I can see benefit mainly in the first patch of the series
(posted the rest for discussion).

I'd like to ask Gustavo whether __counted_by here buys us anything or
whether it's more useful in other parts of kernel (e.g. flexible
allocations in networking code with outer sources of data).

Thanks,
Michal

Download attachment "signature.asc" of type "application/pgp-signature" (266 bytes)