linux-kernel - Re: [PATCH v2] bpf: Add length check for SK_DIAG_BPF_STORAGE_REQ_MAP

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Message-ID: <20230725201142.593ae606@kernel.org>
Date:   Tue, 25 Jul 2023 20:11:42 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Lin Ma <linma@....edu.cn>
Cc:     davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
        ast@...nel.org, martin.lau@...nel.org, yhs@...com,
        void@...ifault.com, andrii@...nel.org, houtao1@...wei.com,
        inwardvessel@...il.com, kuniyu@...zon.com, songliubraving@...com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2] bpf: Add length check for
 SK_DIAG_BPF_STORAGE_REQ_MAP_FD parsing

On Tue, 25 Jul 2023 10:33:30 +0800 Lin Ma wrote:
> The nla_for_each_nested parsing in function bpf_sk_storage_diag_alloc
> does not check the length of the nested attribute. This can lead to an
> out-of-attribute read and allow a malformed nlattr (e.g., length 0) to
> be viewed as a 4 byte integer.
> 
> This patch adds an additional check when the nlattr is getting counted.
> This makes sure the latter nla_get_u32 can access the attributes with
> the correct length.
> 
> Fixes: 1ed4d92458a9 ("bpf: INET_DIAG support in bpf_sk_storage")
> Suggested-by: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Lin Ma <linma@....edu.cn>

Reviewed-by: Jakub Kicinski <kuba@...nel.org>

Those who parse manually must do checks manually. It is what it is.