ppp: defer netns reference release for ppp channel
authorWANG Cong <xiyou.wangcong@gmail.com>
Wed, 6 Jul 2016 05:12:36 +0000 (22:12 -0700)
committerBen Hutchings <ben@decadent.org.uk>
Sun, 20 Nov 2016 01:01:24 +0000 (01:01 +0000)
commit 205e1e255c479f3fd77446415706463b282f94e4 upstream.

Matt reported that we have a NULL pointer dereference
in ppp_pernet() from ppp_connect_channel(),
i.e. pch->chan_net is NULL.

This is due to that a parallel ppp_unregister_channel()
could happen while we are in ppp_connect_channel(), during
which pch->chan_net set to NULL. Since we need a reference
to net per channel, it makes sense to sync the refcnt
with the life time of the channel, therefore we should
release this reference when we destroy it.

Fixes: 1f461dcdd296 ("ppp: take reference on channels netns")
Reported-by: Matt Bennett <Matt.Bennett@alliedtelesis.co.nz>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linux-ppp@vger.kernel.org
Cc: Guillaume Nault <g.nault@alphalink.fr>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

index 9907ac7..4810d26 100644 (file)
@@ -2275,8 +2275,6 @@ ppp_unregister_channel(struct ppp_channel *chan)
-       put_net(pch->chan_net);
-       pch->chan_net = NULL;
        pch->file.dead = 1;
@@ -2883,6 +2881,9 @@ ppp_disconnect_channel(struct channel *pch)
 static void ppp_destroy_channel(struct channel *pch)
+       put_net(pch->chan_net);
+       pch->chan_net = NULL;
        if (!pch->file.dead) {