Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2 2/2] net: return early for possible invalid uaddr | From | Wen Yang <> | Date | Tue, 17 Aug 2021 12:08:39 +0800 |
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在 2021/8/13 上午1:35, Wen Yang 写道: > > > 在 2021/8/12 上午12:11, Eric Dumazet 写道: >> >> >> On 8/11/21 5:24 PM, Wen Yang wrote: >>> The inet_dgram_connect() first calls inet_autobind() to select an >>> ephemeral port, then checks uaddr in udp_pre_connect() or >>> __ip4_datagram_connect(), but the port is not released until the socket >>> is closed. This could cause performance issues or even exhaust ephemeral >>> ports if a malicious user makes a large number of UDP connections with >>> invalid uaddr and/or addr_len. >>> >> >> This is a big patch. >> >> Can the malicious user still use a large number of UDP sockets, >> with valid uaddr/add_len and consequently exhaust ephemeral ports ? >> >> If yes, it does not seem your patch is helping. >> > > Thank you for your comments. > However, we could make these optimizations: > > 1, If the user passed in some invalid parameters, we should return as > soon as possible. We shouldn't assume that these parameters are valid > first, then do some real work (such as select an ephemeral port), and > then finally check that they are indeed valid or not. > > 2. Unify the code for checking parameters in udp_pre_connect() and > __ip4_datagram_connect() to make the code clearer. > >> If no, have you tried instead to undo the autobind, if the connect >> fails ? >> > > Thanks. Undo the autobind is useful if the connect fails. > We will add this logic and submit the v3 patch later. >
Hello, there is no undo autobind for udp. If this logic is added, the patch will be bigger; maybe we can release this ephemeral port through unhash()?
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 8a8dba7..43947d8 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -563,6 +563,7 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr, int addr_len, int flags) { struct sock *sk = sock->sk; + bool autobind; int err;
if (addr_len < sizeof(uaddr->sa_family)) @@ -581,9 +582,17 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr, return err; }
- if (data_race(!inet_sk(sk)->inet_num) && inet_autobind(sk)) + autobind = data_race(!inet_sk(sk)->inet_num); + if (autobind && inet_autobind(sk)) return -EAGAIN; - return sk->sk_prot->connect(sk, uaddr, addr_len); + + err = sk->sk_prot->connect(sk, uaddr, addr_len); + if (err && autobind) { + if (sk->sk_prot->unhash) + sk->sk_prot->unhash(sk); + } + + return err; } EXPORT_SYMBOL(inet_dgram_connect);
Could you kindly give some suggestions? In addition, the previous v2 patch detects errors before bind and returns earlier, which should be reasonable.
-- Best wishes, Wen
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