linux-kernel - Re: [RFC/PATCH bpf-next 1/3] bpf: Add kmem

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: <ZvoIIoxQvL7sHy__@google.com>
Date: Sun, 29 Sep 2024 19:08:34 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [RFC/PATCH bpf-next 1/3] bpf: Add kmem_cache iterator

On Sun, Sep 29, 2024 at 10:04:00AM -0700, Alexei Starovoitov wrote:
> On Fri, Sep 27, 2024 at 11:41 AM Namhyung Kim <namhyung@...nel.org> wrote:
> > +static void *kmem_cache_iter_seq_start(struct seq_file *seq, loff_t *pos)
> > +{
> > +       loff_t cnt = 0;
> > +       struct kmem_cache *s = NULL;
> > +
> > +       mutex_lock(&slab_mutex);
> 
> It would be better to find a way to iterate slabs without holding
> the mutex for the duration of the loop.
> Maybe use refcnt to hold the kmem_cache while bpf prog is looking at it?

Do you mean that you want to not hold slab_mutex while BPF program is
running?  Maybe we can allocates an arary of pointers to the slab cahe
(with refcounts) at the beginning and iterate them instead.  And call
kmem_cache_destroy() for each entry at the end.  Is it ok to you?

Thanks,
Namhyung