From: Eric Dumazet edumazet@google.com
[ Upstream commit 4c971d2f3548e4f11b1460ac048f5307e4b39fdb ]
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 edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/ip.h | 2 +- include/net/sock.h | 5 +++-- net/ipv6/datagram.c | 6 +++--- net/ipv6/udp.c | 11 ++++++----- 4 files changed, 13 insertions(+), 11 deletions(-)
diff --git a/include/net/ip.h b/include/net/ip.h index 0161137914cf..26fffda78cca 100644 --- a/include/net/ip.h +++ b/include/net/ip.h @@ -94,7 +94,7 @@ static inline void ipcm_init_sk(struct ipcm_cookie *ipcm,
ipcm->sockc.mark = inet->sk.sk_mark; ipcm->sockc.tsflags = inet->sk.sk_tsflags; - ipcm->oif = inet->sk.sk_bound_dev_if; + ipcm->oif = READ_ONCE(inet->sk.sk_bound_dev_if); ipcm->addr = inet->inet_saddr; }
diff --git a/include/net/sock.h b/include/net/sock.h index c4b91fc19b9c..3c4fb8f03fd9 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -2866,13 +2866,14 @@ static inline void sk_pacing_shift_update(struct sock *sk, int val) */ static inline bool sk_dev_equal_l3scope(struct sock *sk, int dif) { + int bound_dev_if = READ_ONCE(sk->sk_bound_dev_if); int mdif;
- if (!sk->sk_bound_dev_if || sk->sk_bound_dev_if == dif) + if (!bound_dev_if || bound_dev_if == dif) return true;
mdif = l3mdev_master_ifindex_by_index(sock_net(sk), dif); - if (mdif && mdif == sk->sk_bound_dev_if) + if (mdif && mdif == bound_dev_if) return true;
return false; diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c index 206f66310a88..0324e2685016 100644 --- a/net/ipv6/datagram.c +++ b/net/ipv6/datagram.c @@ -218,11 +218,11 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, 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 7f0fa9bd9ffe..a535c3f2e4af 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 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) }
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;