Messages in this thread | | | From | Kuniyuki Iwashima <> | Subject | Re: [PATCH v1 net 5/5] tcp: Fix data races around icsk->icsk_af_ops. | Date | Tue, 27 Sep 2022 09:48:24 -0700 |
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From: Eric Dumazet <edumazet@google.com> Date: Tue, 27 Sep 2022 09:39:37 -0700 > On Tue, Sep 27, 2022 at 9:33 AM Kuniyuki Iwashima <kuniyu@amazon.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.
No, I haven't. Could you provide the URL? I'm happy to include the syzbot tag and KCSAN report in the changelog.
> > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.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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