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Date: Tue, 6 Jun 2023 08:49:19 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: "luwei (O)" <luwei32@huawei.com>
Cc: Networking <netdev@vger.kernel.org>
Subject: Re: [Question] integer overflow in function
 __qdisc_calculate_pkt_len()
Message-ID: <20230606084919.5549dd58@kernel.org>
In-Reply-To: <c6ab254d-76c3-7507-3935-e9bad4da0bab@huawei.com>
References: <7723cc01-57bf-2b64-7f78-98a0e6508a2e@huawei.com>
	<20230605161922.5e417434@kernel.org>
	<c6ab254d-76c3-7507-3935-e9bad4da0bab@huawei.com>
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On Tue, 6 Jun 2023 20:54:47 +0800 luwei (O) wrote:
> > on a quick look limiting the cell_align to S16_MIN at the netlink level
> > (NLA_POLICY_MIN()) seems reasonable, feel free to send a patch.
> > . =20
>=20
> Thanks for your reply, but do your mean cell_align or overhead? It seems=
=20
> limit cell_align to
>=20
> S16_MIN(-32768) can still cause the overflow:
>=20
>  =C2=A0=C2=A0=C2=A0 66 + (-2147483559) + (-32767) =3D 2147451036
>=20
>    skb->len =3D 66
>    stab->szopts.overhead =3D -2147483559
>    stab->szopts.cell_align =3D -32767

Could you explain what the problem caused by the overflow will be?