Re: Possible netlink autobind regression
flat view
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: 2015-09-17 05:15:24
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Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
On Wed, Sep 16, 2015 at 10:02:00PM -0700, Cong Wang wrote:
This part doesn't look correct, seems it is checking if this is a kernel netlink socket rather than if it is bound. But I am not sure...
Good point. I've changed it so that bound is only set for non-kernel
sockets.
---8<---
netlink: Fix autobind race condition that leads to zero port ID
The commit c0bb07df7d981e4091432754e30c9c720e2c0c78 ("netlink:
Reset portid after netlink_insert failure") introduced a race
condition where if two threads tried to autobind the same socket
one of them may end up with a zero port ID.
This patch reverts that commit and instead fixes it by introducing
a separte "bound" variable to indicate whether a user-space socket
has been bound.
Fixes: c0bb07df7d98 ("netlink: Reset portid after netlink_insert failure")
Reported-by: Tejun Heo <tj@kernel.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Cong Wang <redacted>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index dea9253..42013c5 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c@@ -1068,7 +1068,7 @@ static int netlink_insert(struct sock *sk, u32 portid) lock_sock(sk); err = -EBUSY; - if (nlk_sk(sk)->portid) + if (nlk_sk(sk)->bound) goto err; err = -ENOMEM;
@@ -1083,10 +1083,12 @@ static int netlink_insert(struct sock *sk, u32 portid) if (err) { if (err == -EEXIST) err = -EADDRINUSE; - nlk_sk(sk)->portid = 0; sock_put(sk); + goto err; } + nlk_sk(sk)->bound = !!portid; + err: release_sock(sk); return err;
@@ -1253,7 +1255,7 @@ static int netlink_release(struct socket *sock) skb_queue_purge(&sk->sk_write_queue); - if (nlk->portid) { + if (nlk->bound) { struct netlink_notify n = { .net = sock_net(sk), .protocol = sk->sk_protocol,
@@ -1487,7 +1489,7 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr, return err; } - if (nlk->portid) + if (nlk->bound) if (nladdr->nl_pid != nlk->portid) return -EINVAL;
@@ -1505,7 +1507,7 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr, } } - if (!nlk->portid) { + if (!nlk->bound) { err = nladdr->nl_pid ? netlink_insert(sk, nladdr->nl_pid) : netlink_autobind(sock);
@@ -1553,7 +1555,7 @@ static int netlink_connect(struct socket *sock, struct sockaddr *addr, !netlink_allowed(sock, NL_CFG_F_NONROOT_SEND)) return -EPERM; - if (!nlk->portid) + if (!nlk->bound) err = netlink_autobind(sock); if (err == 0) {
@@ -2371,7 +2373,7 @@ static int netlink_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) dst_group = nlk->dst_group; } - if (!nlk->portid) { + if (!nlk->bound) { err = netlink_autobind(sock); if (err) goto out;
diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h
index 8900840..e6aae40 100644
--- a/net/netlink/af_netlink.h
+++ b/net/netlink/af_netlink.h@@ -35,6 +35,7 @@ struct netlink_sock { unsigned long state; size_t max_recvmsg_len; wait_queue_head_t wait; + bool bound; bool cb_running; struct netlink_callback cb; struct mutex *cb_mutex;
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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