[PATCH 5.15 088/139] net-timestamp: convert sk->sk_tskey to atomic_t

Greg Kroah-Hartman
2022-02-28T17:59:44Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit a1cdec57e03a1352e92fbbe7974039dda4efcec0 ]

UDP sendmsg() can be lockless, this is causing all kinds
of data races.

This patch converts sk->sk_tskey to remove one of these races.

BUG: KCSAN: data-race in __ip_append_data / __ip_append_data

read to 0xffff8881035d4b6c of 4 bytes by task 8877 on cpu 1:
__ip_append_data+0x1c1/0x1de0 net/ipv4/ip_output.c:994
ip_make_skb+0x13f/0x2d0 net/ipv4/ip_output.c:1636
udp_sendmsg+0x12bd/0x14c0 net/ipv4/udp.c:1249
inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:819
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+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff8881035d4b6c of 4 bytes by task 8880 on cpu 0:
__ip_append_data+0x1d8/0x1de0 net/ipv4/ip_output.c:994
ip_make_skb+0x13f/0x2d0 net/ipv4/ip_output.c:1636
udp_sendmsg+0x12bd/0x14c0 net/ipv4/udp.c:1249
inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:819
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+0x44/0xd0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000054d -> 0x0000054e

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8880 Comm: syz-executor.5 Not tainted 5.17.0-rc2-syzkaller-00167-gdcb85f85fa6f-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Fixes: 09c2d251b707 ("net-timestamp: add key to disambiguate concurrent datagrams")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@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/sock.h | 4 ++--
net/can/j1939/transport.c | 2 +-
net/core/skbuff.c | 2 +-
net/core/sock.c | 4 ++--
net/ipv4/ip_output.c | 2 +-
net/ipv6/ip6_output.c | 2 +-
6 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index dfb92f91d5be5..7d49196a3880e 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -506,7 +506,7 @@ struct sock {
u16 sk_tsflags;
int sk_bind_phc;
u8 sk_shutdown;
- u32 sk_tskey;
+ atomic_t sk_tskey;
atomic_t sk_zckey;

u8 sk_clockid;
@@ -2598,7 +2598,7 @@ static inline void _sock_tx_timestamp(struct sock *sk, __u16 tsflags,
__sock_tx_timestamp(tsflags, tx_flags);
if (tsflags & SOF_TIMESTAMPING_OPT_ID && tskey &&
tsflags & SOF_TIMESTAMPING_TX_RECORD_MASK)
- *tskey = sk->sk_tskey++;
+ *tskey = atomic_inc_return(&sk->sk_tskey) - 1;
}
if (unlikely(sock_flag(sk, SOCK_WIFI_STATUS)))
*tx_flags |= SKBTX_WIFI_STATUS;
diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c
index a271688780a2c..307ee1174a6e2 100644
--- a/net/can/j1939/transport.c
+++ b/net/can/j1939/transport.c
@@ -2006,7 +2006,7 @@ struct j1939_session *j1939_tp_send(struct j1939_priv *priv,
/* set the end-packet for broadcast */
session->pkt.last = session->pkt.total;

- skcb->tskey = session->sk->sk_tskey++;
+ skcb->tskey = atomic_inc_return(&session->sk->sk_tskey) - 1;
session->tskey = skcb->tskey;

return session;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index bb4dce8fd0405..449a96e358ad5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4844,7 +4844,7 @@ static void __skb_complete_tx_timestamp(struct sk_buff *skb,
serr->ee.ee_data = skb_shinfo(skb)->tskey;
if (sk->sk_protocol == IPPROTO_TCP &&
sk->sk_type == SOCK_STREAM)
- serr->ee.ee_data -= sk->sk_tskey;
+ serr->ee.ee_data -= atomic_read(&sk->sk_tskey);
}

err = sock_queue_err_skb(sk, skb);
diff --git a/net/core/sock.c b/net/core/sock.c
index 6ea317f84edd2..deaed1b206823 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -866,9 +866,9 @@ int sock_set_timestamping(struct sock *sk, int optname,
if ((1 << sk->sk_state) &
(TCPF_CLOSE | TCPF_LISTEN))
return -EINVAL;
- sk->sk_tskey = tcp_sk(sk)->snd_una;
+ atomic_set(&sk->sk_tskey, tcp_sk(sk)->snd_una);
} else {
- sk->sk_tskey = 0;
+ atomic_set(&sk->sk_tskey, 0);
}
}

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index a4d2eb691cbc1..131066d0319a2 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -992,7 +992,7 @@ static int __ip_append_data(struct sock *sk,

if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
- tskey = sk->sk_tskey++;
+ tskey = atomic_inc_return(&sk->sk_tskey) - 1;

hh_len = LL_RESERVED_SPACE(rt->dst.dev);

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index ff4e83e2a5068..22bf8fb617165 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1465,7 +1465,7 @@ static int __ip6_append_data(struct sock *sk,

if (cork->tx_flags & SKBTX_ANY_SW_TSTAMP &&
sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
- tskey = sk->sk_tskey++;
+ tskey = atomic_inc_return(&sk->sk_tskey) - 1;

hh_len = LL_RESERVED_SPACE(rt->dst.dev);

--
2.34.1