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Message-ID: <CANn89iLyqG8SRmHhWZOZUc-HDR88z_TNZn4_zbJz5MW4+kh2ZQ@mail.gmail.com> Date: Tue, 27 Sep 2022 09:39:37 -0700 From: Eric Dumazet <edumazet@...gle.com> To: Kuniyuki Iwashima <kuniyu@...zon.com> Cc: "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>, Kuniyuki Iwashima <kuni1840@...il.com>, netdev <netdev@...r.kernel.org>, syzkaller-bugs <syzkaller-bugs@...glegroups.com>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v1 net 5/5] tcp: Fix data races around icsk->icsk_af_ops. On Tue, Sep 27, 2022 at 9:33 AM Kuniyuki Iwashima <kuniyu@...zon.com> wrote: > > IPV6_ADDRFORM changes icsk->icsk_af_ops under lock_sock(), but > tcp_(get|set)sockopt() read it locklessly. To avoid load/store > tearing, we need to add READ_ONCE() and WRITE_ONCE() for the reads > and write. I am pretty sure I have released a syzkaller bug recently with this issue. Have you seen this? If yes, please include the appropriate syzbot tag. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com> > --- > net/ipv4/tcp.c | 10 ++++++---- > net/ipv6/ipv6_sockglue.c | 3 ++- > 2 files changed, 8 insertions(+), 5 deletions(-) > > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > index e373dde1f46f..c86dd0ccef5b 100644 > --- a/net/ipv4/tcp.c > +++ b/net/ipv4/tcp.c > @@ -3795,8 +3795,9 @@ int tcp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval, > const struct inet_connection_sock *icsk = inet_csk(sk); > > if (level != SOL_TCP) > - return icsk->icsk_af_ops->setsockopt(sk, level, optname, > - optval, optlen); > + /* IPV6_ADDRFORM can change icsk->icsk_af_ops under us. */ > + return READ_ONCE(icsk->icsk_af_ops)->setsockopt(sk, level, optname, > + optval, optlen); > return do_tcp_setsockopt(sk, level, optname, optval, optlen); > } > EXPORT_SYMBOL(tcp_setsockopt); > @@ -4394,8 +4395,9 @@ int tcp_getsockopt(struct sock *sk, int level, int optname, char __user *optval, > struct inet_connection_sock *icsk = inet_csk(sk); > > if (level != SOL_TCP) > - return icsk->icsk_af_ops->getsockopt(sk, level, optname, > - optval, optlen); > + /* IPV6_ADDRFORM can change icsk->icsk_af_ops under us. */ > + return READ_ONCE(icsk->icsk_af_ops)->getsockopt(sk, level, optname, > + optval, optlen); > return do_tcp_getsockopt(sk, level, optname, optval, optlen); > } > EXPORT_SYMBOL(tcp_getsockopt); > diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c > index a89db5872dc3..726d95859898 100644 > --- a/net/ipv6/ipv6_sockglue.c > +++ b/net/ipv6/ipv6_sockglue.c > @@ -479,7 +479,8 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname, > > /* Paired with READ_ONCE(sk->sk_prot) in inet6_stream_ops */ > WRITE_ONCE(sk->sk_prot, &tcp_prot); > - icsk->icsk_af_ops = &ipv4_specific; > + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ > + WRITE_ONCE(icsk->icsk_af_ops, &ipv4_specific); > sk->sk_socket->ops = &inet_stream_ops; > sk->sk_family = PF_INET; > tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); > -- > 2.30.2 >
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