linux-kernel - Re: nvme-tcp: fix a possible UAF when failing to send request

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Message-Id: <D7OOGIOAJRUH.9LOJ3X4IUKQV@bsdbackstore.eu>
Date: Mon, 10 Feb 2025 11:01:39 +0100
From: "Maurizio Lombardi" <mlombard@...backstore.eu>
To: "zhang.guanghui@...tc.cn" <zhang.guanghui@...tc.cn>, "sagi"
 <sagi@...mberg.me>, "mgurtovoy" <mgurtovoy@...dia.com>, "kbusch"
 <kbusch@...nel.org>, "sashal" <sashal@...nel.org>, "chunguang.xu"
 <chunguang.xu@...pee.com>
Cc: "linux-kernel" <linux-kernel@...r.kernel.org>, "linux-nvme"
 <linux-nvme@...ts.infradead.org>, "linux-block"
 <linux-block@...r.kernel.org>
Subject: Re: nvme-tcp: fix a possible UAF when failing to send request

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

I guess you have to fix your mail client.

>
>     When using the nvme-tcp driver in a storage cluster, the driver may trigger a null pointer causing the host to crash several times.
> By analyzing the vmcore, we know the direct cause is that  the request->mq_hctx was used after free. 
>
>
> CPU1                                                                   CPU2
>
> nvme_tcp_poll                                                          nvme_tcp_try_send  --failed to send reqrest 13

This simply looks like a race condition between nvme_tcp_poll() and nvme_tcp_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