linux-kernel - Re: [PATCH net] bpf: fix allocation warnings in bpf maps and integer overflow

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Message-ID: <CACT4Y+YXEfpE4wa1byedf6m2iqzVsx6V6r7FEDiLw0WKRmA0Ew@mail.gmail.com>
Date:	Mon, 30 Nov 2015 15:16:27 +0100
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	syzkaller <syzkaller@...glegroups.com>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	David Miller <davem@...emloft.net>,
	Alexei Starovoitov <ast@...nel.org>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: [PATCH net] bpf: fix allocation warnings in bpf maps and integer overflow

On Mon, Nov 30, 2015 at 3:13 PM, Daniel Borkmann <daniel@...earbox.net> wrote:
> On 11/30/2015 02:57 PM, Dmitry Vyukov wrote:
> ...
>>
>> kamlloc produces a WARNING if you try to allocate more than it ever
>> possibly can (KMALLOC_SHIFT_MAX).
>
>
> Sure, I understand that.
>
> The kzalloc() in array_map_alloc() is however with __GFP_NOWARN flag
> already.
> The warning only triggers in mm if:
>
>   WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN));
>
> Your test case is using ca.map_type = 1, which is BPF_MAP_TYPE_HASH. So on
> update you're triggering the kmalloc() in htab_map_update_elem().
>
> I'm just asking about the added change in array map.


Then, sorry.
Let's wait for Alexei.
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