From: Ursula Braun ubraun@linux.ibm.com
commit 86434744fedf0cfe07a9eee3f4632c0e25c1d136 upstream.
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@syzkaller.appspotmail.com Fixes: 6d6dd528d5af ("net/smc: fix refcount non-blocking connect() -part 2") Signed-off-by: Ursula Braun ubraun@linux.ibm.com Signed-off-by: Karsten Graul kgraul@linux.ibm.com Signed-off-by: Jakub Kicinski jakub.kicinski@netronome.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/smc/af_smc.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
--- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -854,6 +854,8 @@ static int smc_connect(struct socket *so 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; @@ -1716,8 +1718,6 @@ static int smc_setsockopt(struct socket sk->sk_err = smc->clcsock->sk->sk_err; sk->sk_error_report(sk); } - if (rc) - return rc;
if (optlen < sizeof(int)) return -EINVAL; @@ -1725,6 +1725,8 @@ static int smc_setsockopt(struct socket return -EFAULT;
lock_sock(sk); + if (rc || smc->use_fallback) + goto out; switch (optname) { case TCP_ULP: case TCP_FASTOPEN: @@ -1736,15 +1738,14 @@ static int smc_setsockopt(struct socket 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); } @@ -1753,7 +1754,7 @@ static int smc_setsockopt(struct socket 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); } @@ -1764,6 +1765,7 @@ static int smc_setsockopt(struct socket default: break; } +out: release_sock(sk);
return rc;