[PATCH AUTOSEL 5.12 16/39] inet: annotate data race in inet_send_prepare() and inet_dgram_connect()

Sasha Levin
2021-06-21T17:53:04Z

From: Eric Dumazet <edumazet@google.com>

[ 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@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>
---
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 1355e6c0d567..faa7856c7fb0 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -575,7 +575,7 @@ 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);
}
@@ -803,7 +803,7 @@ 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