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Date: Thu, 12 Dec 2019 22:35:58 +0100
From: Karsten Graul <kgraul@...ux.ibm.com>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org, linux-s390@...r.kernel.org,
heiko.carstens@...ibm.com, raspl@...ux.ibm.com,
ubraun@...ux.ibm.com
Subject: [PATCH net] net/smc: add fallback check to connect()
From: Ursula Braun <ubraun@...ux.ibm.com>
FASTOPEN setsockopt() or sendmsg() may switch the SMC socket to fallback
mode. Once fallback mode is active, the native TCP socket functions are
called. Nevertheless there is a small race window, when FASTOPEN
setsockopt/sendmsg runs in parallel to a connect(), and switch the
socket into fallback mode before connect() takes the sock lock.
Make sure the SMC-specific connect setup is omitted in this case.
This way a syzbot-reported refcount problem is fixed, triggered by
different threads running non-blocking connect() and FASTOPEN_KEY
setsockopt.
Reported-by: syzbot+96d3f9ff6a86d37e44c8@...kaller.appspotmail.com
Fixes: 6d6dd528d5af ("net/smc: fix refcount non-blocking connect() -part 2")
Signed-off-by: Ursula Braun <ubraun@...ux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@...ux.ibm.com>
---
net/smc/af_smc.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index b997072c72e5..cee5bf4a9bb9 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -857,6 +857,8 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr,
goto out;
sock_hold(&smc->sk); /* sock put in passive closing */
+ if (smc->use_fallback)
+ goto out;
if (flags & O_NONBLOCK) {
if (schedule_work(&smc->connect_work))
smc->connect_nonblock = 1;
@@ -1721,8 +1723,6 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
sk->sk_err = smc->clcsock->sk->sk_err;
sk->sk_error_report(sk);
}
- if (rc)
- return rc;
if (optlen < sizeof(int))
return -EINVAL;
@@ -1730,6 +1730,8 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
return -EFAULT;
lock_sock(sk);
+ if (rc || smc->use_fallback)
+ goto out;
switch (optname) {
case TCP_ULP:
case TCP_FASTOPEN:
@@ -1741,15 +1743,14 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
smc_switch_to_fallback(smc);
smc->fallback_rsn = SMC_CLC_DECL_OPTUNSUPP;
} else {
- if (!smc->use_fallback)
- rc = -EINVAL;
+ rc = -EINVAL;
}
break;
case TCP_NODELAY:
if (sk->sk_state != SMC_INIT &&
sk->sk_state != SMC_LISTEN &&
sk->sk_state != SMC_CLOSED) {
- if (val && !smc->use_fallback)
+ if (val)
mod_delayed_work(system_wq, &smc->conn.tx_work,
0);
}
@@ -1758,7 +1759,7 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
if (sk->sk_state != SMC_INIT &&
sk->sk_state != SMC_LISTEN &&
sk->sk_state != SMC_CLOSED) {
- if (!val && !smc->use_fallback)
+ if (!val)
mod_delayed_work(system_wq, &smc->conn.tx_work,
0);
}
@@ -1769,6 +1770,7 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
default:
break;
}
+out:
release_sock(sk);
return rc;
--
2.21.0
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