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Message-ID: <183333fc-e824-5c85-7c44-270474f5473a@openvz.org>
Date:   Tue, 7 Jun 2022 15:37:51 +0300
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Subject: Re: [PATCH memcg v6] net: set proper memcg for net_init hooks
 allocations
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To:     Shakeel Butt <shakeelb@google.com>
Cc:     Qian Cai <quic_qiancai@quicinc.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Andrew Morton <akpm@linux-foundation.org>, kernel@openvz.org,
        LKML <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        =?UTF-8?Q?Michal_Koutn=c3=bd?= <mkoutny@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@suse.com>,
        Florian Westphal <fw@strlen.de>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Eric Dumazet <edumazet@google.com>,
        Cgroups <cgroups@vger.kernel.org>
References: <6b362c6e-9c80-4344-9430-b831f9871a3c@openvz.org>
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 <CALvZod7+tpgKSQpMAgNKDtcsimcSjoh4rbKmUsy3G=QcRHci+Q@mail.gmail.com>
From:   Vasily Averin <vvs@openvz.org>
In-Reply-To: <CALvZod7+tpgKSQpMAgNKDtcsimcSjoh4rbKmUsy3G=QcRHci+Q@mail.gmail.com>
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On 6/7/22 08:58, Shakeel Butt wrote:
> On Mon, Jun 6, 2022 at 11:45 AM Vasily Averin <vvs@openvz.org> wrote:
>>
> [...]
>>
>> As far as I understand this report means that 'init_net' have incorrect
>> virtual address on arm64.
> 
> So, the two call stacks tell the addresses belong to the kernel
> modules (nfnetlink and nf_tables) whose underlying memory is allocated
> through vmalloc and virt_to_page() does not work on vmalloc()
> addresses.

However in both these cases get_mem_cgroup_from_obj() -> mem_cgroup_from_obj() ->
virt_to_folio() -> virt_to_page() -> virt_to_pfn() -> __virt_to_phys() 
handles address of struct net taken from for_each_net().
The only net namespace that exists at this stage is init_net,
and dmesg output confirms this:
"virt_to_phys used for non-linear address: ffffd8efe2d2fe00 (init_net)"

>> Roman, Shakeel, I need your help
>>
>> Should we perhaps verify kaddr via virt_addr_valid() before using virt_to_page()
>> If so, where it should be checked?
> 
> I think virt_addr_valid() check in mem_cgroup_from_obj() should work
> but I think it is expensive on the arm64 platform. The cheaper and a
> bit hacky way to avoid such addresses is to directly use
> is_vmalloc_addr() directly.

I do not understand why you mean that processed address is vmalloc-specific.
As far as I understand it is valid address of static variable, and for some reason
arm64 does not consider them valid virtual addresses.

Thank you,
	Vasily Averin