netdev - Re: [PATCH bpf-next v3 02/12] net, sk_msg: Annotate lockless access to sk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200122225752.caxnk5sylskbrzsg@kafai-mbp.dhcp.thefacebook.com>
Date:   Wed, 22 Jan 2020 22:57:55 +0000
From:   Martin Lau <kafai@...com>
To:     Jakub Sitnicki <jakub@...udflare.com>
CC:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kernel-team@...udflare.com" <kernel-team@...udflare.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        "John Fastabend" <john.fastabend@...il.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: Re: [PATCH bpf-next v3 02/12] net, sk_msg: Annotate lockless access
 to sk_prot on clone

On Wed, Jan 22, 2020 at 02:05:39PM +0100, Jakub Sitnicki wrote:
> sk_msg and ULP frameworks override protocol callbacks pointer in
> sk->sk_prot, while tcp accesses it locklessly when cloning the listening
> socket, that is with neither sk_lock nor sk_callback_lock held.
> 
> Once we enable use of listening sockets with sockmap (and hence sk_msg),
> there will be shared access to sk->sk_prot if socket is getting cloned
> while being inserted/deleted to/from the sockmap from another CPU:
> 
> Read side:
> 
> tcp_v4_rcv
>   sk = __inet_lookup_skb(...)
>   tcp_check_req(sk)
>     inet_csk(sk)->icsk_af_ops->syn_recv_sock
>       tcp_v4_syn_recv_sock
>         tcp_create_openreq_child
>           inet_csk_clone_lock
>             sk_clone_lock
>               READ_ONCE(sk->sk_prot)
> 
> Write side:
> 
> sock_map_ops->map_update_elem
>   sock_map_update_elem
>     sock_map_update_common
>       sock_map_link_no_progs
>         tcp_bpf_init
>           tcp_bpf_update_sk_prot
>             sk_psock_update_proto
>               WRITE_ONCE(sk->sk_prot, ops)
> 
> sock_map_ops->map_delete_elem
>   sock_map_delete_elem
>     __sock_map_delete
>      sock_map_unref
>        sk_psock_put
>          sk_psock_drop
>            sk_psock_restore_proto
>              tcp_update_ulp
>                WRITE_ONCE(sk->sk_prot, proto)
> 
> Mark the shared access with READ_ONCE/WRITE_ONCE annotations.
Acked-by: Martin KaFai Lau <kafai@...com>