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SubjectRe: [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@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.


>
> 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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