From f9a11716c8445b496e9fafeec7e8412d384d02e2 Mon Sep 17 00:00:00 2001 From: Sabrina Dubroca Date: Thu, 8 Oct 2026 14:38:32 +0200 Subject: [PATCH] xfrm: espintcp: reorder operations within espintcp_init_sk When enabled on a socket, espintcp sets the socket callbacks to its own before it has finished setting up its context and published it as icsk_ulp_data. Any one of those callbacks that gets called before will dereference a NULL icsk_ulp_data. Fix this by reording the operations, and add memory barriers to ensure callers will have a struct espintcp_ctx available. Add a few WRITE_ONCE/READ_ONCE too while we're there. Fixes: e27cca96cd68 ("xfrm: add espintcp (RFC 8229)") Cc: stable@vger.kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Reported-by: Peihan Liu Reported-by: Yilin Zhu Reported-by: Ren Wei Reported-by: Eulgyu Kim Reported-by: Jaeyoung Chung Link: https://lore.kernel.org/all/c30b645074a1b379e0f7fe297f917c66137d9964.1778464688.git.zylzyl2333@gmail.com/ Link: https://lore.kernel.org/all/20260819155349.3555804-1-jjy600901@snu.ac.kr Signed-off-by: Sabrina Dubroca Signed-off-by: Steffen Klassert --- include/net/espintcp.h | 5 +++-- net/xfrm/espintcp.c | 43 +++++++++++++++++++++++++----------------- 2 files changed, 29 insertions(+), 19 deletions(-) diff --git a/include/net/espintcp.h b/include/net/espintcp.h index c70efd704b6d..7cad3c6822df 100644 --- a/include/net/espintcp.h +++ b/include/net/espintcp.h @@ -34,7 +34,8 @@ static inline struct espintcp_ctx *espintcp_getctx(const struct sock *sk) { const struct inet_connection_sock *icsk = inet_csk(sk); - /* RCU is only needed for diag */ - return (__force void *)icsk->icsk_ulp_data; + /* pairs with smp_wmb() in espintcp_init_sk() */ + smp_rmb(); + return (__force void *)READ_ONCE(icsk->icsk_ulp_data); } #endif diff --git a/net/xfrm/espintcp.c b/net/xfrm/espintcp.c index 3e72b9f067b9..4052ae5bbb2e 100644 --- a/net/xfrm/espintcp.c +++ b/net/xfrm/espintcp.c @@ -434,7 +434,9 @@ static void espintcp_destruct(struct sock *sk) bool tcp_is_ulp_esp(struct sock *sk) { - return sk->sk_prot == &espintcp_prot || sk->sk_prot == &espintcp6_prot; + const struct proto *prot = READ_ONCE(sk->sk_prot); + + return prot == &espintcp_prot || prot == &espintcp6_prot; } EXPORT_SYMBOL_GPL(tcp_is_ulp_esp); @@ -466,34 +468,41 @@ static int espintcp_init_sk(struct sock *sk) __sk_dst_reset(sk); - strp_check_rcv(&ctx->strp); skb_queue_head_init(&ctx->ike_queue); skb_queue_head_init(&ctx->out_queue); + INIT_WORK(&ctx->work, espintcp_tx_work); + + ctx->saved_data_ready = sk->sk_data_ready; + ctx->saved_write_space = sk->sk_write_space; + ctx->saved_destruct = sk->sk_destruct; + + /* avoid using task_frag */ + sk->sk_allocation = GFP_ATOMIC; + sk->sk_use_task_frag = false; + + rcu_assign_pointer(icsk->icsk_ulp_data, ctx); + + /* pairs with smp_rmb() in espintcp_getctx() */ + smp_wmb(); + + WRITE_ONCE(sk->sk_data_ready, espintcp_data_ready); + WRITE_ONCE(sk->sk_write_space, espintcp_write_space); + sk->sk_destruct = espintcp_destruct; if (sk->sk_family == AF_INET) { - sk->sk_prot = &espintcp_prot; - sk->sk_socket->ops = &espintcp_ops; + WRITE_ONCE(sk->sk_prot, &espintcp_prot); + WRITE_ONCE(sk->sk_socket->ops, &espintcp_ops); } else { mutex_lock(&tcpv6_prot_mutex); if (!espintcp6_prot.recvmsg) build_protos(&espintcp6_prot, &espintcp6_ops, sk->sk_prot, sk->sk_socket->ops); mutex_unlock(&tcpv6_prot_mutex); - sk->sk_prot = &espintcp6_prot; - sk->sk_socket->ops = &espintcp6_ops; + WRITE_ONCE(sk->sk_prot, &espintcp6_prot); + WRITE_ONCE(sk->sk_socket->ops, &espintcp6_ops); } - ctx->saved_data_ready = sk->sk_data_ready; - ctx->saved_write_space = sk->sk_write_space; - ctx->saved_destruct = sk->sk_destruct; - sk->sk_data_ready = espintcp_data_ready; - sk->sk_write_space = espintcp_write_space; - sk->sk_destruct = espintcp_destruct; - rcu_assign_pointer(icsk->icsk_ulp_data, ctx); - INIT_WORK(&ctx->work, espintcp_tx_work); - /* avoid using task_frag */ - sk->sk_allocation = GFP_ATOMIC; - sk->sk_use_task_frag = false; + strp_check_rcv(&ctx->strp); return 0;