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([147.46.174.222]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-37a20dbc386sm7260143a91.11.2026.06.14.05.09.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 14 Jun 2026 05:09:51 -0700 (PDT) From: Sechang Lim To: "D . Wythe" , Dust Li , Sidraya Jayagond , Wenjia Zhang , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "David S . Miller" Cc: Mahanta Jambigi , Tony Lu , Wen Gu , Simon Horman , Ursula Braun , Karsten Graul , Guvenc Gulce , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net] net/smc: fix out-of-bounds read in smc_clcsock_data_ready() Date: Sun, 14 Jun 2026 12:09:30 +0000 Message-ID: <20260614120931.4041687-1-rhkrqnwk98@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit smc_clcsock_data_ready() is installed on the listen socket and reads its sk_user_data as an smc_sock. A passive-open child inherits this callback, but sk_clone_lock() clears the child's sk_user_data because it is tagged SK_USER_DATA_NOCOPY. smc_tcp_syn_recv_sock() restores the child's af_ops, but the inherited sk_data_ready() is left in place until accept. In that window the child is established. A cgroup sock_ops program can run bpf_sock_hash_update() on it from tcp_init_transfer(); sk_psock_init() stores a sk_psock in the NULL sk_user_data. The inherited callback then reads sk_user_data via smc_clcsock_user_data(), which masks only SK_USER_DATA_NOCOPY, mistakes the sk_psock for an smc_sock, and reads a callback pointer past the end of the sk_psock: BUG: KASAN: slab-out-of-bounds in smc_clcsock_data_ready+0x84/0x200 net/smc/af_smc.c:2637 Read of size 8 at addr ffff8880013b8674 by task syz.6.12484/67930 smc_clcsock_data_ready+0x84/0x200 net/smc/af_smc.c:2637 tcp_urg+0x24d/0x360 net/ipv4/tcp_input.c:6264 tcp_rcv_state_process+0x280d/0x4940 net/ipv4/tcp_input.c:7336 tcp_child_process+0x371/0xa50 net/ipv4/tcp_minisocks.c:1002 tcp_v4_rcv+0x1eaa/0x2a00 net/ipv4/tcp_ipv4.c:2186 ip_protocol_deliver_rcu+0x226/0x420 net/ipv4/ip_input.c:207 ip_local_deliver_finish+0x35a/0x5f0 net/ipv4/ip_input.c:241 __netif_receive_skb_one_core+0x1e5/0x210 net/core/dev.c:6216 process_backlog+0x631/0x1470 net/core/dev.c:6682 __napi_poll+0xb3/0x320 net/core/dev.c:7749 net_rx_action+0x4fa/0xcb0 net/core/dev.c:7969 handle_softirqs+0x236/0x800 kernel/softirq.c:622 Allocated by task 67930: sk_psock_init+0x142/0x740 net/core/skmsg.c:766 sock_map_link+0x646/0xdf0 net/core/sock_map.c:279 sock_hash_update_common+0xd3/0x990 net/core/sock_map.c:1010 bpf_sock_hash_update+0x114/0x170 net/core/sock_map.c:1229 __cgroup_bpf_run_filter_sock_ops+0x74/0xa0 kernel/bpf/cgroup.c:1727 tcp_init_transfer+0x1085/0x1100 net/ipv4/tcp_input.c:6693 tcp_rcv_state_process+0x241e/0x4940 net/ipv4/tcp_input.c:7231 tcp_child_process+0x371/0xa50 net/ipv4/tcp_minisocks.c:1002 Restore the inherited sk_data_ready() in smc_tcp_syn_recv_sock(), where the child's sk_user_data is already cleared, rather than only at accept. Fixes: a60a2b1e0af1 ("net/smc: reduce active tcp_listen workers") Signed-off-by: Sechang Lim --- net/smc/af_smc.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index b5db69073e20..152971e8ad17 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -156,6 +156,12 @@ static struct sock *smc_tcp_syn_recv_sock(const struct sock *sk, if (child) { rcu_assign_sk_user_data(child, NULL); + /* + * the child inherited the listen-specific sk_data_ready(); + * restore it here, as sk_user_data may be reused before accept + */ + child->sk_data_ready = smc->clcsk_data_ready; + /* v4-mapped sockets don't inherit parent ops. Don't restore. */ if (inet_csk(child)->icsk_af_ops == inet_csk(sk)->icsk_af_ops) inet_csk(child)->icsk_af_ops = smc->ori_af_ops; -- 2.43.0