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[95.169.12.199]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-34f14f2dfbbsm7844370eec.10.2026.10.02.10.38.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Oct 2026 10:38:51 -0700 (PDT) From: Chengfeng Ye To: davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com Cc: horms@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Chengfeng Ye , stable@vger.kernel.org Subject: [PATCH net v4] net: pin protocol module before inet socket allocation Date: Sat, 3 Oct 2026 01:38:44 +0800 Message-ID: <20261002173844.3537111-1-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 inet_create() and inet6_create() look up the protocol under RCU, then drop RCU before using the resulting proto. A concurrent module unload can unregister the protosw, wait for the RCU readers, and destroy the proto's slab before sk_alloc() uses it. sk_alloc() may sleep, so the RCU read-side critical section cannot simply be extended across the allocation. The reported failure occurred during concurrent L2TP socket creation and module unload: Oops: general protection fault, probably for non-canonical address 0xffff1108974182a0 KASAN: maybe wild-memory-access in range [0xfff8a844ba0c1500-0xfff8a844ba0c1507] RIP: kmem_cache_alloc_noprof+0x63/0x370 Call Trace: sk_prot_alloc+0x74/0x2c0 sk_alloc+0x2b/0x6c0 inet_create+0x2cd/0xd40 __sock_create+0x1c3/0x430 __sys_socket+0x116/0x1d0 Cache the proto and its owner under RCU and acquire a temporary module reference before dropping RCU. This prevents normal module unload while the proto is in use. sk_prot_alloc() takes the socket's own reference; drop the temporary reference on every exit after allocation. Use the cached proto for the IPv6 backlog callback as well. Use try_module_get() with its existing initialization semantics. SCTP creates its kernel control socket during module initialization, so rejecting MODULE_STATE_COMING would prevent modular SCTP from loading. Failed module initialization can still unwind published protocols despite module references; that separate publication/unwind lifetime issue is not fixed here. Fixes: a79af59efd20 ("[NET]: Fix module reference counts for loadable protocol modules") Cc: stable@vger.kernel.org Assisted-by: GPT-6-Astra Signed-off-by: Chengfeng Ye --- Changes in v4: - Remove the MODULE_STATE_COMING rejection. SCTP creates its kernel control socket from module init and must be allowed to use the published protosw. - Keep the owner cached under RCU and use the cached proto for IPv6 backlog setup, retaining those v3 changes. - Scope the module-reference guarantee to normal module unload. The earlier review's initialization-failure unwind concern remains a separate issue; rejecting all initializing modules is not a compatible solution. - Rebase onto net/main at a7bfaba4823e. v3: https://lore.kernel.org/r/20260904111514.584264-1-nicoyip.dev@gmail.com/ Review: https://lore.kernel.org/r/178887699602.219967.13594894510710999619@kernel.org/ v2: https://lore.kernel.org/r/20260825172349.232794-1-nicoyip.dev@gmail.com/ v1: https://lore.kernel.org/r/20260823171311.3857087-1-nicoyip.dev@gmail.com/ net/ipv4/af_inet.c | 14 +++++++++++--- net/ipv6/af_inet6.c | 16 ++++++++++++---- 2 files changed, 23 insertions(+), 7 deletions(-) diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 32d006c1a8ee..c956afa65ec4 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -263,6 +263,7 @@ static int inet_create(struct net *net, struct socket *sock, int protocol, struct inet_protosw *answer; struct inet_sock *inet; struct proto *answer_prot; + struct module *answer_owner; unsigned char answer_flags; int try_loading_module = 0; int err; @@ -322,9 +323,14 @@ static int inet_create(struct net *net, struct socket *sock, int protocol, !ns_capable(net->user_ns, CAP_NET_RAW)) goto out_rcu_unlock; - sock->ops = answer->ops; answer_prot = answer->prot; + answer_owner = answer_prot->owner; answer_flags = answer->flags; + if (!try_module_get(answer_owner)) { + err = -EPROTONOSUPPORT; + goto out_rcu_unlock; + } + sock->ops = answer->ops; rcu_read_unlock(); WARN_ON(!answer_prot->slab); @@ -332,7 +338,7 @@ static int inet_create(struct net *net, struct socket *sock, int protocol, err = -ENOMEM; sk = sk_alloc(net, PF_INET, GFP_KERNEL, answer_prot, kern); if (!sk) - goto out; + goto out_module_put; err = 0; if (INET_PROTOSW_REUSE & answer_flags) @@ -398,6 +404,8 @@ static int inet_create(struct net *net, struct socket *sock, int protocol, if (err) goto out_sk_release; } +out_module_put: + module_put(answer_owner); out: return err; out_rcu_unlock: @@ -406,7 +414,7 @@ static int inet_create(struct net *net, struct socket *sock, int protocol, out_sk_release: sk_common_release(sk); sock->sk = NULL; - goto out; + goto out_module_put; } diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c index 282912a11999..9db60af6f38d 100644 --- a/net/ipv6/af_inet6.c +++ b/net/ipv6/af_inet6.c @@ -110,6 +110,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol, struct sock *sk; struct inet_protosw *answer; struct proto *answer_prot; + struct module *answer_owner; unsigned char answer_flags; int try_loading_module = 0; int err; @@ -167,9 +168,14 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol, !ns_capable(net->user_ns, CAP_NET_RAW)) goto out_rcu_unlock; - sock->ops = answer->ops; answer_prot = answer->prot; + answer_owner = answer_prot->owner; answer_flags = answer->flags; + if (!try_module_get(answer_owner)) { + err = -EPROTONOSUPPORT; + goto out_rcu_unlock; + } + sock->ops = answer->ops; rcu_read_unlock(); WARN_ON(!answer_prot->slab); @@ -177,7 +183,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol, err = -ENOBUFS; sk = sk_alloc(net, PF_INET6, GFP_KERNEL, answer_prot, kern); if (!sk) - goto out; + goto out_module_put; sock_init_data(sock, sk); @@ -201,7 +207,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol, sk->sk_family = PF_INET6; sk->sk_protocol = protocol; - sk->sk_backlog_rcv = answer->prot->backlog_rcv; + sk->sk_backlog_rcv = answer_prot->backlog_rcv; inet_sk(sk)->pinet6 = np = inet6_sk_generic(sk); np->hop_limit = -1; @@ -251,6 +257,8 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol, if (err) goto out_sk_release; } +out_module_put: + module_put(answer_owner); out: return err; out_rcu_unlock: @@ -259,7 +267,7 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol, out_sk_release: sk_common_release(sk); sock->sk = NULL; - goto out; + goto out_module_put; } int __inet6_bind(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len, base-commit: a7bfaba4823e3c165bb2004c74eff7c096672bc7 -- 2.43.0