The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

f49cd2f4d617 ("tcp: Fix data races around icsk->icsk_af_ops.") 34704ef024ae ("bpf: net: Change do_tcp_getsockopt() to take the sockptr_t argument") 086d49058cd8 ("ipv6: annotate some data-races around sk->sk_prot") b3cb764aa1d7 ("net: drop nopreempt requirement on sock_prot_inuse_add()") 2a12ae5d433d ("net: inline sock_prot_inuse_add()") f4bd73b5a950 ("af_unix: Return errno instead of NULL in unix_create1().") 94531cfcbe79 ("af_unix: Add unix_stream_proto for sockmap") 0b8464459858 ("unix_bpf: Fix a potential deadlock in unix_dgram_bpf_recvmsg()") 9825d866ce0d ("af_unix: Implement unix_dgram_bpf_recvmsg()") c63829182c37 ("af_unix: Implement ->psock_update_sk_prot()") c7272e15f0f1 ("af_unix: Add a dummy ->close() for sockmap") 29df44fa52b7 ("af_unix: Implement ->read_sock() for sockmap") 34e5b0118685 ("sctp: delay auto_asconf init until binding the first addr") 3914d88f7608 ("xsk: Respect device's headroom and tailroom on generic xmit path") b8af417e4d93 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f49cd2f4d6170d27a2c61f1fecb03d8a70c91f57 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima kuniyu@amazon.com Date: Thu, 6 Oct 2022 11:53:49 -0700 Subject: [PATCH] tcp: Fix data races around icsk->icsk_af_ops.

setsockopt(IPV6_ADDRFORM) and tcp_v6_connect() change icsk->icsk_af_ops under lock_sock(), but tcp_(get|set)sockopt() read it locklessly. To avoid load/store tearing, we need to add READ_ONCE() and WRITE_ONCE() for the reads and writes.

Thanks to Eric Dumazet for providing the syzbot report:

BUG: KCSAN: data-race in tcp_setsockopt / tcp_v6_connect

write to 0xffff88813c624518 of 8 bytes by task 23936 on cpu 0: tcp_v6_connect+0x5b3/0xce0 net/ipv6/tcp_ipv6.c:240 __inet_stream_connect+0x159/0x6d0 net/ipv4/af_inet.c:660 inet_stream_connect+0x44/0x70 net/ipv4/af_inet.c:724 __sys_connect_file net/socket.c:1976 [inline] __sys_connect+0x197/0x1b0 net/socket.c:1993 __do_sys_connect net/socket.c:2003 [inline] __se_sys_connect net/socket.c:2000 [inline] __x64_sys_connect+0x3d/0x50 net/socket.c:2000 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88813c624518 of 8 bytes by task 23937 on cpu 1: tcp_setsockopt+0x147/0x1c80 net/ipv4/tcp.c:3789 sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3585 __sys_setsockopt+0x212/0x2b0 net/socket.c:2252 __do_sys_setsockopt net/socket.c:2263 [inline] __se_sys_setsockopt net/socket.c:2260 [inline] __x64_sys_setsockopt+0x62/0x70 net/socket.c:2260 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0xffffffff8539af68 -> 0xffffffff8539aff8

Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 23937 Comm: syz-executor.5 Not tainted 6.0.0-rc4-syzkaller-00331-g4ed9c1e971b1-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot syzkaller@googlegroups.com Reported-by: Eric Dumazet edumazet@google.com Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Signed-off-by: Jakub Kicinski kuba@kernel.org

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 0c51abeee172..f8232811a5be 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3796,8 +3796,9 @@ int tcp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval, const struct inet_connection_sock *icsk = inet_csk(sk);

if (level != SOL_TCP) - return icsk->icsk_af_ops->setsockopt(sk, level, optname, - optval, optlen); + /* Paired with WRITE_ONCE() in do_ipv6_setsockopt() and tcp_v6_connect() */ + return READ_ONCE(icsk->icsk_af_ops)->setsockopt(sk, level, optname, + optval, optlen); return do_tcp_setsockopt(sk, level, optname, optval, optlen); } EXPORT_SYMBOL(tcp_setsockopt); @@ -4396,8 +4397,9 @@ int tcp_getsockopt(struct sock *sk, int level, int optname, char __user *optval, struct inet_connection_sock *icsk = inet_csk(sk);

if (level != SOL_TCP) - return icsk->icsk_af_ops->getsockopt(sk, level, optname, - optval, optlen); + /* Paired with WRITE_ONCE() in do_ipv6_setsockopt() and tcp_v6_connect() */ + return READ_ONCE(icsk->icsk_af_ops)->getsockopt(sk, level, optname, + optval, optlen); return do_tcp_getsockopt(sk, level, optname, USER_SOCKPTR(optval), USER_SOCKPTR(optlen)); } diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c index d7207a546aec..532f4478c884 100644 --- a/net/ipv6/ipv6_sockglue.c +++ b/net/ipv6/ipv6_sockglue.c @@ -479,7 +479,8 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,

/* Paired with READ_ONCE(sk->sk_prot) in inet6_stream_ops */ WRITE_ONCE(sk->sk_prot, &tcp_prot); - icsk->icsk_af_ops = &ipv4_specific; + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ + WRITE_ONCE(icsk->icsk_af_ops, &ipv4_specific); sk->sk_socket->ops = &inet_stream_ops; sk->sk_family = PF_INET; tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index a8adda623da1..2a3f9296df1e 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -238,7 +238,8 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr, sin.sin_port = usin->sin6_port; sin.sin_addr.s_addr = usin->sin6_addr.s6_addr32[3];

- icsk->icsk_af_ops = &ipv6_mapped; + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ + WRITE_ONCE(icsk->icsk_af_ops, &ipv6_mapped); if (sk_is_mptcp(sk)) mptcpv6_handle_mapped(sk, true); sk->sk_backlog_rcv = tcp_v4_do_rcv; @@ -250,7 +251,8 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,

if (err) { icsk->icsk_ext_hdr_len = exthdrlen; - icsk->icsk_af_ops = &ipv6_specific; + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ + WRITE_ONCE(icsk->icsk_af_ops, &ipv6_specific); if (sk_is_mptcp(sk)) mptcpv6_handle_mapped(sk, false); sk->sk_backlog_rcv = tcp_v6_do_rcv;