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

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Message-ID: <83f40245-7953-9f5c-3191-3d9f4d50f9bb@iogearbox.net>
Date:   Tue, 21 May 2019 16:48:03 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Martin KaFai Lau <kafai@...com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...com>, kernel-team@...com,
        Joe Stringer <joe@...valent.com>
Subject: Re: [PATCH bpf] bpf: Check sk_fullsock() before returning from
 bpf_sk_lookup()

On 05/17/2019 11:21 PM, Martin KaFai Lau 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>

Applied, thanks!