linux-kernel - Re: [RFC/PATCH bpf-next 2/3] mm/bpf: Add bpf_get_kmem

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Message-ID: <ZvoIZYyyl73A-D51@google.com>
Date: Sun, 29 Sep 2024 19:09:41 -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 2/3] mm/bpf: Add bpf_get_kmem_cache() kfunc

On Sun, Sep 29, 2024 at 10:05:42AM -0700, Alexei Starovoitov wrote:
> On Fri, Sep 27, 2024 at 11:41 AM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > +__bpf_kfunc struct kmem_cache *bpf_get_kmem_cache(u64 addr)
> > +{
> > +       struct slab *slab;
> > +
> > +       slab = virt_to_slab((void *)(long)addr);
> > +       return slab ? slab->slab_cache : NULL;
> > +}
> 
> I think this needs more safety guards on 'addr'.
> It needs to check the valid range of 'addr' before doing virt_to_slab.

Ok, I think we can use virt_addr_valid() for that.

Thanks,
Namhyung