linux-kernel - Re: [PATCH rfc 10/12] mm: introduce bpf_out_of

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: <aBC7_2Fv3NFuad4R@tiehlicka>
Date: Tue, 29 Apr 2025 13:46:07 +0200
From: Michal Hocko <mhocko@...e.com>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Suren Baghdasaryan <surenb@...gle.com>,
	David Rientjes <rientjes@...gle.com>, Josh Don <joshdon@...gle.com>,
	Chuyi Zhou <zhouchuyi@...edance.com>, cgroups@...r.kernel.org,
	linux-mm@...ck.org, bpf@...r.kernel.org
Subject: Re: [PATCH rfc 10/12] mm: introduce bpf_out_of_memory() bpf kfunc

On Mon 28-04-25 03:36:15, Roman Gushchin wrote:
> Introduce bpf_out_of_memory() bpf kfunc, which allows to declare
> an out of memory events and trigger the corresponding kernel OOM
> handling mechanism.
> 
> It takes a trusted memcg pointer (or NULL for system-wide OOMs)
> as an argument, as well as the page order.
> 
> Only one OOM can be declared and handled in the system at once,
> so if the function is called in parallel to another OOM handling,
> it bails out with -EBUSY.

This makes sense for the global OOM handler because concurrent handlers
are cooperative. But is this really correct for memcg ooms which could
happen for different hierarchies? Currently we do block on oom_lock in
that case to make sure one oom doesn't starve others. Do we want the
same behavior for custom OOM handlers?

-- 
Michal Hocko
SUSE Labs