netdev - Re: [PATCH bpf] bpf: Check sk_fullsock() before returning from bpf_sk

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Date:   Mon, 20 May 2019 11:57:37 -0700
From:   Joe Stringer <joe@...valent.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     bpf@...r.kernel.org, Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf] bpf: Check sk_fullsock() before returning from bpf_sk_lookup()

On Fri, May 17, 2019 at 2:21 PM Martin KaFai Lau <kafai@...com> wrote:
>
> The BPF_FUNC_sk_lookup_xxx helpers return RET_PTR_TO_SOCKET_OR_NULL.
> Meaning a fullsock ptr and its fullsock's fields in bpf_sock can be
> accessed, e.g. type, protocol, mark and priority.
> Some new helper, like bpf_sk_storage_get(), also expects
> ARG_PTR_TO_SOCKET is a fullsock.
>
> bpf_sk_lookup() currently calls sk_to_full_sk() before returning.
> However, the ptr returned from sk_to_full_sk() is not guaranteed
> to be a fullsock.  For example, it cannot get a fullsock if sk
> is in TCP_TIME_WAIT.
>
> This patch checks for sk_fullsock() before returning. If it is not
> a fullsock, sock_gen_put() is called if needed and then returns NULL.
>
> Fixes: 6acc9b432e67 ("bpf: Add helper to retrieve socket in BPF")
> Cc: Joe Stringer <joe@...valent.com>
> Signed-off-by: Martin KaFai Lau <kafai@...com>
> ---

Acked-by: Joe Stringer <joe@...valent.com>