Re: [PATCH bpf v2] net: bpf: don't leak time wait and request sockets

[Martin Lau]

On Fri, Jan 10, 2020 at 01:23:36PM +0000, Lorenz Bauer wrote:
> It's possible to leak time wait and request sockets via the following
> BPF pseudo code:
>  
>   sk = bpf_skc_lookup_tcp(...)
>   if (sk)
>     bpf_sk_release(sk)
> 
> If sk->sk_state is TCP_NEW_SYN_RECV or TCP_TIME_WAIT the refcount taken
> by bpf_skc_lookup_tcp is not undone by bpf_sk_release. This is because
> sk_flags is re-used for other data in both kinds of sockets. The check
> 
>   !sock_flag(sk, SOCK_RCU_FREE)
> 
> therefore returns a bogus result. Check that sk_flags is valid by calling
> sk_fullsock. Skip checking SOCK_RCU_FREE if we already know that sk is
> not a full socket.
Acked-by: Martin KaFai Lau <kafai@xxxxxx>