From: Eric Dumazet edumazet@google.com
[ Upstream commit 5e5265522a9a7f91d1b0bd411d634bdaf16c80cd ]
TCP request sockets are lockless, some of their fields can change while being read by another cpu as syzbot noticed.
This is usually harmless, but we should annotate the known races.
This patch takes care of tcp_rsk(req)->txhash, a separate one is needed for tcp_rsk(req)->ts_recent.
BUG: KCSAN: data-race in tcp_make_synack / tcp_rtx_synack
write to 0xffff8881362304bc of 4 bytes by task 32083 on cpu 1: tcp_rtx_synack+0x9d/0x2a0 net/ipv4/tcp_output.c:4213 inet_rtx_syn_ack+0x38/0x80 net/ipv4/inet_connection_sock.c:880 tcp_check_req+0x379/0xc70 net/ipv4/tcp_minisocks.c:665 tcp_v6_rcv+0x125b/0x1b20 net/ipv6/tcp_ipv6.c:1673 ip6_protocol_deliver_rcu+0x92f/0xf30 net/ipv6/ip6_input.c:437 ip6_input_finish net/ipv6/ip6_input.c:482 [inline] NF_HOOK include/linux/netfilter.h:303 [inline] ip6_input+0xbd/0x1b0 net/ipv6/ip6_input.c:491 dst_input include/net/dst.h:468 [inline] ip6_rcv_finish+0x1e2/0x2e0 net/ipv6/ip6_input.c:79 NF_HOOK include/linux/netfilter.h:303 [inline] ipv6_rcv+0x74/0x150 net/ipv6/ip6_input.c:309 __netif_receive_skb_one_core net/core/dev.c:5452 [inline] __netif_receive_skb+0x90/0x1b0 net/core/dev.c:5566 netif_receive_skb_internal net/core/dev.c:5652 [inline] netif_receive_skb+0x4a/0x310 net/core/dev.c:5711 tun_rx_batched+0x3bf/0x400 tun_get_user+0x1d24/0x22b0 drivers/net/tun.c:1997 tun_chr_write_iter+0x18e/0x240 drivers/net/tun.c:2043 call_write_iter include/linux/fs.h:1871 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x4ab/0x7d0 fs/read_write.c:584 ksys_write+0xeb/0x1a0 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] __se_sys_write fs/read_write.c:646 [inline] __x64_sys_write+0x42/0x50 fs/read_write.c:646 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
read to 0xffff8881362304bc of 4 bytes by task 32078 on cpu 0: tcp_make_synack+0x367/0xb40 net/ipv4/tcp_output.c:3663 tcp_v6_send_synack+0x72/0x420 net/ipv6/tcp_ipv6.c:544 tcp_conn_request+0x11a8/0x1560 net/ipv4/tcp_input.c:7059 tcp_v6_conn_request+0x13f/0x180 net/ipv6/tcp_ipv6.c:1175 tcp_rcv_state_process+0x156/0x1de0 net/ipv4/tcp_input.c:6494 tcp_v6_do_rcv+0x98a/0xb70 net/ipv6/tcp_ipv6.c:1509 tcp_v6_rcv+0x17b8/0x1b20 net/ipv6/tcp_ipv6.c:1735 ip6_protocol_deliver_rcu+0x92f/0xf30 net/ipv6/ip6_input.c:437 ip6_input_finish net/ipv6/ip6_input.c:482 [inline] NF_HOOK include/linux/netfilter.h:303 [inline] ip6_input+0xbd/0x1b0 net/ipv6/ip6_input.c:491 dst_input include/net/dst.h:468 [inline] ip6_rcv_finish+0x1e2/0x2e0 net/ipv6/ip6_input.c:79 NF_HOOK include/linux/netfilter.h:303 [inline] ipv6_rcv+0x74/0x150 net/ipv6/ip6_input.c:309 __netif_receive_skb_one_core net/core/dev.c:5452 [inline] __netif_receive_skb+0x90/0x1b0 net/core/dev.c:5566 netif_receive_skb_internal net/core/dev.c:5652 [inline] netif_receive_skb+0x4a/0x310 net/core/dev.c:5711 tun_rx_batched+0x3bf/0x400 tun_get_user+0x1d24/0x22b0 drivers/net/tun.c:1997 tun_chr_write_iter+0x18e/0x240 drivers/net/tun.c:2043 call_write_iter include/linux/fs.h:1871 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x4ab/0x7d0 fs/read_write.c:584 ksys_write+0xeb/0x1a0 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] __se_sys_write fs/read_write.c:646 [inline] __x64_sys_write+0x42/0x50 fs/read_write.c:646 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x91d25731 -> 0xe79325cd
Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 32078 Comm: syz-executor.4 Not tainted 6.5.0-rc1-syzkaller-00033-geb26cbb1a754 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023
Fixes: 58d607d3e52f ("tcp: provide skb->hash to synack packets") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Reviewed-by: Kuniyuki Iwashima kuniyu@amazon.com Link: https://lore.kernel.org/r/20230717144445.653164-2-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/tcp_ipv4.c | 3 ++- net/ipv4/tcp_minisocks.c | 2 +- net/ipv4/tcp_output.c | 4 ++-- net/ipv6/tcp_ipv6.c | 2 +- 4 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index ef740983a1222..e5df50b3e23a0 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -992,7 +992,8 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb, 0, tcp_md5_do_lookup(sk, l3index, addr, AF_INET), inet_rsk(req)->no_srccheck ? IP_REPLY_ARG_NOSRCCHECK : 0, - ip_hdr(skb)->tos, tcp_rsk(req)->txhash); + ip_hdr(skb)->tos, + READ_ONCE(tcp_rsk(req)->txhash)); }
/* diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 7f37e7da64671..f281eab7fd125 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -510,7 +510,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk, newicsk->icsk_ack.lrcvtime = tcp_jiffies32;
newtp->lsndtime = tcp_jiffies32; - newsk->sk_txhash = treq->txhash; + newsk->sk_txhash = READ_ONCE(treq->txhash); newtp->total_retrans = req->num_retrans;
tcp_init_xmit_timers(newsk); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 925594dbeb929..693a29d3f43bd 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3581,7 +3581,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, rcu_read_lock(); md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req)); #endif - skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4); + skb_set_hash(skb, READ_ONCE(tcp_rsk(req)->txhash), PKT_HASH_TYPE_L4); /* bpf program will be interested in the tcp_flags */ TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK; tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5, @@ -4124,7 +4124,7 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
/* Paired with WRITE_ONCE() in sock_setsockopt() */ if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED) - tcp_rsk(req)->txhash = net_tx_rndhash(); + WRITE_ONCE(tcp_rsk(req)->txhash, net_tx_rndhash()); res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL, NULL); if (!res) { diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 8d61efeab9c99..0dcb06a1fe044 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1133,7 +1133,7 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb, req->ts_recent, sk->sk_bound_dev_if, tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->saddr, l3index), ipv6_get_dsfield(ipv6_hdr(skb)), 0, sk->sk_priority, - tcp_rsk(req)->txhash); + READ_ONCE(tcp_rsk(req)->txhash)); }