From: Lorenz Bauer <lmb@cloudflare.com>
To: kafai@fb.com, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
"David S. Miller" <davem@davemloft.net>,
Lorenz Bauer <lmb@cloudflare.com>,
Joe Stringer <joe@isovalent.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: kernel-team@cloudflare.com
Subject: [PATCH bpf v2] net: bpf: don't leak time wait and request sockets
Date: Fri, 10 Jan 2020 13:23:36 +0000 [thread overview]
Message-ID: <20200110132336.26099-1-lmb@cloudflare.com> (raw)
In-Reply-To: <20200109115749.12283-1-lmb@cloudflare.com>
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.
Fixes: edbf8c01de5a ("bpf: add skc_lookup_tcp helper")
Fixes: f7355a6c0497 ("bpf: Check sk_fullsock() before returning from bpf_sk_lookup()")
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
---
net/core/filter.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index 42fd17c48c5f..41820ba0774c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5277,8 +5277,7 @@ __bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
if (sk) {
sk = sk_to_full_sk(sk);
if (!sk_fullsock(sk)) {
- if (!sock_flag(sk, SOCK_RCU_FREE))
- sock_gen_put(sk);
+ sock_gen_put(sk);
return NULL;
}
}
@@ -5315,8 +5314,7 @@ bpf_sk_lookup(struct sk_buff *skb, struct bpf_sock_tuple *tuple, u32 len,
if (sk) {
sk = sk_to_full_sk(sk);
if (!sk_fullsock(sk)) {
- if (!sock_flag(sk, SOCK_RCU_FREE))
- sock_gen_put(sk);
+ sock_gen_put(sk);
return NULL;
}
}
@@ -5383,7 +5381,8 @@ static const struct bpf_func_proto bpf_sk_lookup_udp_proto = {
BPF_CALL_1(bpf_sk_release, struct sock *, sk)
{
- if (!sock_flag(sk, SOCK_RCU_FREE))
+ /* Only full sockets have sk->sk_flags. */
+ if (!sk_fullsock(sk) || !sock_flag(sk, SOCK_RCU_FREE))
sock_gen_put(sk);
return 0;
}
--
2.20.1
next prev parent reply other threads:[~2020-01-10 13:25 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-09 11:57 [PATCH bpf 0/1] Fix memory leak in helpers dealing with sockets Lorenz Bauer
2020-01-09 11:57 ` [PATCH bpf 1/1] net: bpf: don't leak time wait and request sockets Lorenz Bauer
2020-01-09 18:23 ` Martin Lau
2020-01-10 13:27 ` Lorenz Bauer
2020-01-10 13:23 ` Lorenz Bauer [this message]
2020-01-10 16:43 ` [PATCH bpf v2] " Martin Lau
2020-01-10 18:45 ` Alexei Starovoitov
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