From: Mahanta Jambigi <mjambigi@linux.ibm.com>
To: Chengfeng Ye <nicoyip.dev@gmail.com>,
"D. Wythe" <alibuda@linux.alibaba.com>,
Dust Li <dust.li@linux.alibaba.com>,
Sidraya Jayagond <sidraya@linux.ibm.com>,
Tony Lu <tonylu@linux.alibaba.com>,
Wen Gu <guwen@linux.alibaba.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Simon Horman <horms@kernel.org>,
Wenjia Zhang <wenjia@linux.ibm.com>
Cc: linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH net] net/smc: serialize sndbuf descriptor release with diagnostic dumps
Date: Mon, 28 Sep 2026 11:26:50 +0530 [thread overview]
Message-ID: <7960d73e-e316-4853-8398-144742e866d3@linux.ibm.com> (raw)
In-Reply-To: <20260927073203.3694279-1-nicoyip.dev@gmail.com>
On 27/09/26 1:02 pm, Chengfeng Ye wrote:
> An SMC-D connection can remain in the socket hash while smc_conn_kill()
> tears it down. For devices supporting DMB nocopy, smcd_buf_detach() frees
> the send buffer descriptor without taking the hash lock held by the
> diagnostic reader.
>
> __smc_diag_dump() can load a non-NULL conn->sndbuf_desc, then a concurrent
> smc_conn_kill() can clear the pointer and free the descriptor before the
> dump reads its len field. The socket lock held by the teardown path does
> not exclude the dump, and clearing the pointer before freeing it does
> not protect a reader that has already loaded it.
Agreed. This is addressed in v6[1] by unhashing the socket at the top of
smc_conn_kill(), before smcd_buf_detach() runs, so no hashed socket can
have its sndbuf_desc freed under a concurrent diag reader.
[1]
https://lore.kernel.org/netdev/20260926065023.1629497-1-mjambigi@linux.ibm.com/
next prev parent reply other threads:[~2026-09-28 5:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-27 7:32 Chengfeng Ye
2026-09-28 5:56 ` Mahanta Jambigi [this message]
2026-09-28 6:16 ` Chengfeng Ye
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