Messages in this thread | | | Date | Wed, 16 Sep 2015 22:02:00 -0700 | Subject | Re: Possible netlink autobind regression | From | Cong Wang <> |
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On Wed, Sep 16, 2015 at 8:41 PM, Herbert Xu <herbert@gondor.apana.org.au> wrote: > On Thu, Sep 17, 2015 at 11:08:45AM +0800, Herbert Xu wrote: >> >> Good catch! I think your explanation makes perfect sense. Linus >> ran into this previously too after suspend-and-resume. > > Unfortunately you can't just postpone the setting of portid because > once you pass it onto rhashtable the portid must never change while > it's in custody. > > So what I've done is essentially revert my previous fix and instead > add a new boolean "bound" to indicate whether the socket has been > bound. > > ---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 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>
We saw similar soft lockup with the one Tejun reported, in our data center.
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Just one comment below.
[...]
> @@ -1285,7 +1287,7 @@ 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,
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...
Other than this, looks good to me:
Reviewed-by: Cong Wang <cwang@twopensource.com>
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