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Wed, 21 Oct 2026 10:13:27 -0700 (PDT) Received: from Terra.tail0ac356.ts.net ([198.176.50.208]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3674198f1d8sm12947635eec.24.2026.10.21.10.13.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2026 10:13:26 -0700 (PDT) From: Weiming Shi To: "D. Wythe" , Dust Li , Sidraya Jayagond , Mahanta Jambigi , Tony Lu , Wen Gu , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: Ursula Braun , Karsten Graul , linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Xiang Mei , Weiming Shi , stable@vger.kernel.org Subject: [PATCH] net/smc: reject CDC messages after connection teardown Date: Wed, 21 Oct 2026 10:12:57 -0700 Message-ID: <20261021171256.166870-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.56.0 X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit smc_cdc_rx_handler() drops the link group's connection lock after looking up a connection. Concurrent close(2) can then set conn->freed and release a registration-failed receive buffer before the receive handler obtains the socket lock. The handler subsequently dereferences the released descriptor. KASAN reports: BUG: KASAN: slab-use-after-free in smc_cdc_msg_recv (net/smc/smc_cdc.c:376 net/smc/smc_cdc.c:431) Read of size 4 at addr ffff8881064a4720 by task kworker/u48:2/233 Workqueue: rxe_wq do_work Call Trace: smc_cdc_msg_recv (net/smc/smc_cdc.c:376 net/smc/smc_cdc.c:431) smc_cdc_rx_handler (net/smc/smc_cdc.c:503) smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445 net/smc/smc_wr.c:459 net/smc/smc_wr.c:498) tasklet_action_common (kernel/softirq.c:961) handle_softirqs (kernel/softirq.c:645) do_softirq (kernel/softirq.c:546 (discriminator 19) kernel/softirq.c:533 (discriminator 19)) Freed by task 209: __kasan_slab_free (mm/kasan/common.c:285) kfree (./include/linux/kasan.h:235 mm/slub.c:2748 mm/slub.c:6508 mm/slub.c:6801) smc_conn_free (net/smc/smc_core.c:1244 net/smc/smc_core.c:1283) __smc_release (net/smc/af_smc.c:322) smc_release (net/smc/af_smc.c:361) __sock_release (net/socket.c:735) sock_close (net/socket.c:1526 (discriminator 1)) __fput (fs/file_table.c:512) fput_close_sync (fs/file_table.c:617) __do_sys_close (fs/open.c:1560) The buggy address is located 32 bytes inside of freed 128-byte region [ffff8881064a4700, ffff8881064a4780) Kernel panic - not syncing: KASAN: panic_on_warn set ... Both smc_conn_free() and CDC message processing run under the socket lock. Check conn->freed after acquiring that lock. Discard messages which passed the lookup before teardown. This keeps the existing lock order and prevents access to receive buffers released by smc_conn_free(). Fixes: a6920d1d130c ("net/smc: handle unregistered buffers") Cc: stable@vger.kernel.org Reported-by: Xiang Mei Assisted-by: LLM Signed-off-by: Weiming Shi --- net/smc/smc_cdc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c index 32d6d03df321..499a2473b79b 100644 --- a/net/smc/smc_cdc.c +++ b/net/smc/smc_cdc.c @@ -428,7 +428,8 @@ static void smc_cdc_msg_recv(struct smc_sock *smc, struct smc_cdc_msg *cdc) { sock_hold(&smc->sk); bh_lock_sock(&smc->sk); - smc_cdc_msg_recv_action(smc, cdc); + if (!smc->conn.freed) + smc_cdc_msg_recv_action(smc, cdc); bh_unlock_sock(&smc->sk); sock_put(&smc->sk); /* no free sk in softirq-context */ } -- 2.56.0