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[95.169.12.199]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-351735e316fsm9920870eec.11.2026.10.08.01.44.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2026 01:45:01 -0700 (PDT) From: Chengfeng Ye To: "D . Wythe" , Dust Li , Sidraya Jayagond , Mahanta Jambigi Cc: Tony Lu , Wen Gu , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Chengfeng Ye Subject: [PATCH net v3] net/smc: protect clcsock lifetime in smc_getname Date: Thu, 8 Oct 2026 16:44:44 +0800 Message-ID: <20261008084444.787449-1-nicoyip.dev@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit smc_getname() dereferences smc->clcsock without holding clcsock_release_lock. Link-group termination can release the CLC socket through smc_close_active_abort() while the SMC socket is still open, for example after shutdown(SHUT_WR). A getsockname() caller can load smc->clcsock, then the termination worker can clear the pointer and call sock_release() before the caller accesses clcsock->ops or invokes getname(). This causes a use-after-free; if the worker clears the pointer before the load, it causes a NULL dereference. The syscall's file reference keeps the SMC socket alive but does not prevent asynchronous release of its CLC socket. KASAN reported the following with test-only timing instrumentation: BUG: KASAN: slab-use-after-free in smc_getname+0x19e/0x1b0 Read of size 8 at addr ffff888109abb4e0 by task poc/103 Call Trace: smc_getname+0x19e/0x1b0 do_getsockname+0xe5/0x170 __sys_getsockname+0x8c/0x100 Allocated by task 95: sock_alloc_inode+0x1e/0x280 sock_alloc+0x3d/0x240 __sock_create+0x7e/0x430 smc_create+0x121/0x240 Freed by task 0: kmem_cache_free+0xcc/0x340 rcu_core+0x50a/0x1850 Last potentially related work creation: evict+0x446/0x6c0 smc_clcsock_release+0xa8/0xd0 smc_close_active_abort+0x26a/0x3a0 __smc_lgr_terminate.part.0+0x137/0x2e0 Hold clcsock_release_lock across the pointer check and the getname() callback to serialize with smc_clcsock_release(). Return -EBADF if the CLC socket has already been released, preserving the existing peer state check and the callback's return value otherwise. Fixes: b03faa1fafc8 ("net/smc: postpone release of clcsock") Cc: stable@vger.kernel.org Assisted-by: GPT-6.1-Sol Signed-off-by: Chengfeng Ye --- Changes in v3: - Limit the fix to smc_getname(), as requested by Mahanta. The code change is identical to v1 and uses the existing release mutex. - Drop the new clcsock_lock and the other v2 changes. Mahanta will address the other readers through the broader CLC lifetime changes discussed with Dust Li. - Rebase onto current net/main; keep the stable Cc. Review: https://lore.kernel.org/r/4bb7f15e-2cd8-4598-9bab-1ea5f5d2bb59@linux.ibm.com/ v2: https://lore.kernel.org/r/20261003183325.2289707-1-nicoyip.dev@gmail.com/ v1: https://lore.kernel.org/r/20260926180404.2721010-1-nicoyip.dev@gmail.com/ Validation: W=1 builds of net/smc/ passed with IPv6 enabled and disabled. The KASAN excerpt is the original report; no runtime test was run for v3. net/smc/af_smc.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index e9f93b3ab435b..8b3ee70f8433f 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -2784,6 +2784,7 @@ int smc_getname(struct socket *sock, struct sockaddr *addr, int peer) { struct smc_sock *smc; + int rc = -EBADF; if (peer && (sock->sk->sk_state != SMC_ACTIVE) && (sock->sk->sk_state != SMC_APPCLOSEWAIT1)) @@ -2791,7 +2792,11 @@ int smc_getname(struct socket *sock, struct sockaddr *addr, smc = smc_sk(sock->sk); - return smc->clcsock->ops->getname(smc->clcsock, addr, peer); + mutex_lock(&smc->clcsock_release_lock); + if (smc->clcsock) + rc = smc->clcsock->ops->getname(smc->clcsock, addr, peer); + mutex_unlock(&smc->clcsock_release_lock); + return rc; } int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) base-commit: 6d25ffca055a77787c21a36b66c253f76239411b -- 2.43.0