From 4c971d2f3548e4f11b1460ac048f5307e4b39fdb Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 13 May 2022 11:55:41 -0700 Subject: net: annotate races around sk->sk_bound_dev_if UDP sendmsg() is lockless, and reads sk->sk_bound_dev_if while this field can be changed by another thread. Adds minimal annotations to avoid KCSAN splats for UDP. Following patches will add more annotations to potential lockless readers. BUG: KCSAN: data-race in __ip6_datagram_connect / udpv6_sendmsg write to 0xffff888136d47a94 of 4 bytes by task 7681 on cpu 0: __ip6_datagram_connect+0x6e2/0x930 net/ipv6/datagram.c:221 ip6_datagram_connect+0x2a/0x40 net/ipv6/datagram.c:272 inet_dgram_connect+0x107/0x190 net/ipv4/af_inet.c:576 __sys_connect_file net/socket.c:1900 [inline] __sys_connect+0x197/0x1b0 net/socket.c:1917 __do_sys_connect net/socket.c:1927 [inline] __se_sys_connect net/socket.c:1924 [inline] __x64_sys_connect+0x3d/0x50 net/socket.c:1924 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x50 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff888136d47a94 of 4 bytes by task 7670 on cpu 1: udpv6_sendmsg+0xc60/0x16e0 net/ipv6/udp.c:1436 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:652 sock_sendmsg_nosec net/socket.c:705 [inline] sock_sendmsg net/socket.c:725 [inline] ____sys_sendmsg+0x39a/0x510 net/socket.c:2413 ___sys_sendmsg net/socket.c:2467 [inline] __sys_sendmmsg+0x267/0x4c0 net/socket.c:2553 __do_sys_sendmmsg net/socket.c:2582 [inline] __se_sys_sendmmsg net/socket.c:2579 [inline] __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2579 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x50 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x00000000 -> 0xffffff9b Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 7670 Comm: syz-executor.3 Tainted: G W 5.18.0-rc1-syzkaller-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 I chose to not add Fixes: tag because race has minor consequences and stable teams busy enough. Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller --- net/ipv6/datagram.c | 6 +++--- net/ipv6/udp.c | 11 ++++++----- 2 files changed, 9 insertions(+), 8 deletions(-) (limited to 'net/ipv6') diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c index 39b2327edc4e..df665d4e8f0f 100644 --- a/net/ipv6/datagram.c +++ b/net/ipv6/datagram.c @@ -218,11 +218,11 @@ ipv4_connected: err = -EINVAL; goto out; } - sk->sk_bound_dev_if = usin->sin6_scope_id; + WRITE_ONCE(sk->sk_bound_dev_if, usin->sin6_scope_id); } if (!sk->sk_bound_dev_if && (addr_type & IPV6_ADDR_MULTICAST)) - sk->sk_bound_dev_if = np->mcast_oif; + WRITE_ONCE(sk->sk_bound_dev_if, np->mcast_oif); /* Connect to link-local address requires an interface */ if (!sk->sk_bound_dev_if) { @@ -798,7 +798,7 @@ int ip6_datagram_send_ctl(struct net *net, struct sock *sk, if (src_idx) { if (fl6->flowi6_oif && src_idx != fl6->flowi6_oif && - (sk->sk_bound_dev_if != fl6->flowi6_oif || + (READ_ONCE(sk->sk_bound_dev_if) != fl6->flowi6_oif || !sk_dev_equal_l3scope(sk, src_idx))) return -EINVAL; fl6->flowi6_oif = src_idx; diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 3fc97d4621ac..960cfea82016 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -105,7 +105,7 @@ static int compute_score(struct sock *sk, struct net *net, const struct in6_addr *daddr, unsigned short hnum, int dif, int sdif) { - int score; + int bound_dev_if, score; struct inet_sock *inet; bool dev_match; @@ -132,10 +132,11 @@ static int compute_score(struct sock *sk, struct net *net, score++; } - dev_match = udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif); + bound_dev_if = READ_ONCE(sk->sk_bound_dev_if); + dev_match = udp_sk_bound_dev_eq(net, bound_dev_if, dif, sdif); if (!dev_match) return -1; - if (sk->sk_bound_dev_if) + if (bound_dev_if) score++; if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id()) @@ -789,7 +790,7 @@ static bool __udp_v6_is_mcast_sock(struct net *net, struct sock *sk, (inet->inet_dport && inet->inet_dport != rmt_port) || (!ipv6_addr_any(&sk->sk_v6_daddr) && !ipv6_addr_equal(&sk->sk_v6_daddr, rmt_addr)) || - !udp_sk_bound_dev_eq(net, sk->sk_bound_dev_if, dif, sdif) || + !udp_sk_bound_dev_eq(net, READ_ONCE(sk->sk_bound_dev_if), dif, sdif) || (!ipv6_addr_any(&sk->sk_v6_rcv_saddr) && !ipv6_addr_equal(&sk->sk_v6_rcv_saddr, loc_addr))) return false; @@ -1433,7 +1434,7 @@ do_udp_sendmsg: } if (!fl6->flowi6_oif) - fl6->flowi6_oif = sk->sk_bound_dev_if; + fl6->flowi6_oif = READ_ONCE(sk->sk_bound_dev_if); if (!fl6->flowi6_oif) fl6->flowi6_oif = np->sticky_pktinfo.ipi6_ifindex; -- cgit v1.2.3