| Message ID | 20150917051503.GA19978@gondor.apana.org.au |
|---|---|
| State | Superseded, archived |
| Delegated to: | David Miller |
| Headers | show |
On 09/17/15 at 01:15pm, Herbert Xu wrote: > 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 <cwang@twopensource.com> Acked-by: Thomas Graf <tgraf@suug.ch> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello, Herbert. On Thu, Sep 17, 2015 at 01:15:03PM +0800, Herbert Xu wrote: > 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 <cwang@twopensource.com> Maybe add that this led to a deadlock and add a Link tag to this thread? > @@ -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; !! isn't necessasry and this creates ordering between two stores. ->bound must be visible only after ->portid is visible, so this should be smp_store_release(). > @@ -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) { And all unlocked reads should be smp_load_acquire(). > err = netlink_autobind(sock); > if (err) > goto out; Thanks.
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;