From: Eric Dumazet <edumazet@xxxxxxxxxx> [ Upstream commit dcd01eeac14486b56a790f5cce9b823440ba5b34 ] Both functions are known to be racy when reading inet_num as we do not want to grab locks for the common case the socket has been bound already. The race is resolved in inet_autobind() by reading again inet_num under the socket lock. syzbot reported: BUG: KCSAN: data-race in inet_send_prepare / udp_lib_get_port write to 0xffff88812cba150e of 2 bytes by task 24135 on cpu 0: udp_lib_get_port+0x4b2/0xe20 net/ipv4/udp.c:308 udp_v6_get_port+0x5e/0x70 net/ipv6/udp.c:89 inet_autobind net/ipv4/af_inet.c:183 [inline] inet_send_prepare+0xd0/0x210 net/ipv4/af_inet.c:807 inet6_sendmsg+0x29/0x80 net/ipv6/af_inet6.c:639 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg net/socket.c:674 [inline] ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350 ___sys_sendmsg net/socket.c:2404 [inline] __sys_sendmmsg+0x315/0x4b0 net/socket.c:2490 __do_sys_sendmmsg net/socket.c:2519 [inline] __se_sys_sendmmsg net/socket.c:2516 [inline] __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2516 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff88812cba150e of 2 bytes by task 24132 on cpu 1: inet_send_prepare+0x21/0x210 net/ipv4/af_inet.c:806 inet6_sendmsg+0x29/0x80 net/ipv6/af_inet6.c:639 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg net/socket.c:674 [inline] ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350 ___sys_sendmsg net/socket.c:2404 [inline] __sys_sendmmsg+0x315/0x4b0 net/socket.c:2490 __do_sys_sendmmsg net/socket.c:2519 [inline] __se_sys_sendmmsg net/socket.c:2516 [inline] __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2516 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x0000 -> 0x9db4 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 24132 Comm: syz-executor.2 Not tainted 5.13.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- net/ipv4/af_inet.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index b7260c8cef2e..8267349afe23 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -572,7 +572,7 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr, return err; } - if (!inet_sk(sk)->inet_num && inet_autobind(sk)) + if (data_race(!inet_sk(sk)->inet_num) && inet_autobind(sk)) return -EAGAIN; return sk->sk_prot->connect(sk, uaddr, addr_len); } @@ -799,7 +799,7 @@ int inet_send_prepare(struct sock *sk) sock_rps_record_flow(sk); /* We may need to bind the socket. */ - if (!inet_sk(sk)->inet_num && !sk->sk_prot->no_autobind && + if (data_race(!inet_sk(sk)->inet_num) && !sk->sk_prot->no_autobind && inet_autobind(sk)) return -EAGAIN; -- 2.30.2
