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

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Message-Id: <D7QC8AQ7J89A.32TNPSFWV1VNX@bsdbackstore.eu>
Date: Wed, 12 Feb 2025 09:52:01 +0100
From: "Maurizio Lombardi" <mlombard@...backstore.eu>
To: "Maurizio Lombardi" <mlombard@...backstore.eu>,
 "zhang.guanghui@...tc.cn" <zhang.guanghui@...tc.cn>, "chunguang.xu"
 <chunguang.xu@...pee.com>
Cc: "mgurtovoy" <mgurtovoy@...dia.com>, "sagi" <sagi@...mberg.me>, "kbusch"
 <kbusch@...nel.org>, "sashal" <sashal@...nel.org>, "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 Wed Feb 12, 2025 at 9:11 AM CET, Maurizio Lombardi wrote:
> On Tue Feb 11, 2025 at 9:04 AM CET, zhang.guanghui@...tc.cn wrote:
>> Hi 
>>
>>     This is a  race issue,  I can't reproduce it stably yet. I have not tested the latest kernel.  but in fact,  I've synced some nvme-tcp patches from  lastest upstream,
>
> Hello, could you try this patch?
>
> queue_lock should protect against concurrent "error recovery",
> +	mutex_lock(&queue->queue_lock);

Unfortunately I've just realized that queue_lock won't save us
from the race against the controller reset, it's still possible
we lock a destroyed mutex. So just try this
simplified patch, I will try to figure out something else:

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 841238f38fdd..b714e1691c30 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -2660,7 +2660,10 @@ static int nvme_tcp_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob)
 	set_bit(NVME_TCP_Q_POLLING, &queue->flags);
 	if (sk_can_busy_loop(sk) && skb_queue_empty_lockless(&sk->sk_receive_queue))
 		sk_busy_loop(sk, true);
+
+	mutex_lock(&queue->send_mutex);
 	nvme_tcp_try_recv(queue);
+	mutex_unlock(&queue->send_mutex);
 	clear_bit(NVME_TCP_Q_POLLING, &queue->flags);
 	return queue->nr_cqe;
 }

Maurizio