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Date: Mon, 10 Feb 2025 11:01:39 +0100
Message-Id: <D7OOGIOAJRUH.9LOJ3X4IUKQV@bsdbackstore.eu>
Cc: "linux-kernel" <linux-kernel@vger.kernel.org>, "linux-nvme"
 <linux-nvme@lists.infradead.org>, "linux-block"
 <linux-block@vger.kernel.org>
Subject: Re: nvme-tcp: fix a possible UAF when failing to send request
From: "Maurizio Lombardi" <mlombard@bsdbackstore.eu>
To: "zhang.guanghui@cestc.cn" <zhang.guanghui@cestc.cn>, "sagi"
 <sagi@grimberg.me>, "mgurtovoy" <mgurtovoy@nvidia.com>, "kbusch"
 <kbusch@kernel.org>, "sashal" <sashal@kernel.org>, "chunguang.xu"
 <chunguang.xu@shopee.com>
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References: <2025021015413817916143@cestc.cn>
In-Reply-To: <2025021015413817916143@cestc.cn>

On Mon Feb 10, 2025 at 8:41 AM CET, zhang.guanghui@cestc.cn wrote:
> Hello=20
>
>

I guess you have to fix your mail client.

>
> =C2=A0 =C2=A0=C2=A0When using the nvme-tcp driver in a storage cluster, t=
he driver may trigger a null pointer causing the host to crash several time=
s.
> By analyzing the vmcore, we know the direct cause is that=C2=A0 the reque=
st->mq_hctx was used after free.=20
>
>
> CPU1=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0CPU2
>
> nvme_tcp_poll=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 nvme_=
tcp_try_send=C2=A0 --failed to send reqrest 13

This simply looks like a race condition between nvme_tcp_poll() and nvme_tc=
p_try_send()
Personally, I would try to fix it inside the nvme-tcp driver without
touching the core functions.

Maybe nvme_tcp_poll should just ensure that io_work completes before
calling nvme_tcp_try_recv(), the POLLING flag should then prevent io_work
from getting rescheduled by the nvme_tcp_data_ready() callback.


Maurizio