linux-kernel - [PATCH bpf 0/1] Fix memory leak in helpers dealing with sockets

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Message-Id: <20200109115749.12283-1-lmb@cloudflare.com>
Date:   Thu,  9 Jan 2020 11:57:47 +0000
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Lorenz Bauer <lmb@...udflare.com>,
        Martin KaFai Lau <kafai@...com>,
        Joe Stringer <joe@...valent.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     kernel-team@...udflare.com, edumazet@...gle.com
Subject: [PATCH bpf 0/1] Fix memory leak in helpers dealing with sockets

While rolling out a new BPF based TC classifier I hit a memory leak, which
manifests in large numbers of request and time wait sockets not being released.

The root cause is that the current BPF helpers dealing with sockets are naive:
they assume that sk->sk_flags is always valid. struct request_sock and
struct inet_timewait_sock break this.

I've fixed this up by adding a helper that checks sk_state in addition to sk_flags.
The solution is a bit clumsy: it encapsulates details of struct sock in BPF.
It would probably be nicer to have a sock_gen_put + SOCK_RCU_FREE function exposed
in sock.h, but that might be too big a change for backports.

Thoughts?

Lorenz Bauer (1):
  net: bpf: don't leak time wait and request sockets

 net/core/filter.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

-- 
2.20.1