On Tue, Oct 03, 2017 at 06:40:03PM +0200, Guillaume Nault wrote:
> On Tue, Oct 03, 2017 at 09:44:14AM +0200, Beniamino Galvani wrote:
> > Call Trace:
> > ppp_destroy_interface+0xd8/0xe0 [ppp_generic]
> > ppp_disconnect_channel+0xda/0x110 [ppp_generic]
> > ppp_unregister_channel+0x5e/0x110 [ppp_generic]
> > pppox_unbind_sock+0x23/0x30 [pppox]
> > pppoe_connect+0x130/0x440 [pppoe]
> > SYSC_connect+0x98/0x110
> > ? do_fcntl+0x2c0/0x5d0
> > SyS_connect+0xe/0x10
> > entry_SYSCALL_64_fastpath+0x1a/0xa5
> > RIP: 0033:0x7fa71f4af840
> > RSP: 002b:00007ffe4ea40bf8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
> > RAX: ffffffffffffffda RBX: 0000556d37ae0538 RCX: 00007fa71f4af840
> > RDX: 000000000000001e RSI: 00007ffe4ea40c00 RDI: 0000000000000008
> > RBP: 0000556d37b2a1b0 R08: 0000556d396e95b0 R09: 0000000000000008
> > R10: 00000000aaaaaaab R11: 0000000000000246 R12: 0000556d37adc008
> > R13: 0000556d37adc004 R14: 0000556d37b2a1a4 R15: 0000000000000000
> > Code: 04 00 00 04 e8 cb 52 e3 ff 5b 41 5c 41 5d 5d c3 41 0f b7 84 24 32 02 00 00 4c 89 e7 48 29 c7 e8 80 8b aa ff 5b 41 5c 41 5d 5d c3 <0f> 0b 0f 1f 80 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 57 41
> > RIP: free_netdev+0x107/0x110 RSP: ffffc28a40573d88
> > ---[ end trace ed294ff0cc40eeff ]---
> >
> > To reproduce this, establish a PPP connection through pppd, then bring
> > down and delete the ppp interface:
> >
> > # pppd nodetach lock user client plugin rp-pppoe.so ens11 noauth nodeflate password password &
> > Plugin rp-pppoe.so loaded.
> > RP-PPPoE plugin version 3.8p compiled against pppd 2.4.7
> > PPP session is 16
> > Connected to fe:54:00:5f:04:13 via interface ens11
> > Using interface ppp0
> > Connect: ppp0 <--> ens11
> > CHAP authentication succeeded: Access granted
> > CHAP authentication succeeded
> > peer from calling number FE:54:00:5F:04:13 authorized
> > local IP address 3.1.1.10
> > remote IP address 3.1.1.1
> >
> > # ip l set ppp0 down
> > # ip l del ppp0
> >
> > It does not happen every time but only when ppp_destroy_interface() is
> > called with dev->reg_state = UNREGISTERING, set by the concurrent
> > rtnl_delete_link().
> >
> Indeed, we have a race here: ppp_destroy_interface() can be called before
> netdev_run_todo() completes. I'm working on it.
>
Sorry for the delay, I've followed a few complicated dead ends before
getting to this simple and rather obvious fix.
Can you try this patch?
-------- 8< --------
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index c3f77e3b7819..e365866600ba 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -1339,7 +1339,17 @@ ppp_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats64)
static int ppp_dev_init(struct net_device *dev)
{
+ struct ppp *ppp;
+
netdev_lockdep_set_classes(dev);
+
+ ppp = netdev_priv(dev);
+ /* Let the netdevice take a reference on the ppp file. This ensures
+ * that ppp_destroy_interface() won't run before the device gets
+ * unregistered.
+ */
+ atomic_inc(&ppp->file.refcnt);
+
return 0;
}
@@ -1362,6 +1372,15 @@ static void ppp_dev_uninit(struct net_device *dev)
wake_up_interruptible(&ppp->file.rwait);
}
+static void ppp_dev_priv_destructor(struct net_device *dev)
+{
+ struct ppp *ppp;
+
+ ppp = netdev_priv(dev);
+ if (atomic_dec_and_test(&ppp->file.refcnt))
+ ppp_destroy_interface(ppp);
+}
+
static const struct net_device_ops ppp_netdev_ops = {
.ndo_init = ppp_dev_init,
.ndo_uninit = ppp_dev_uninit,
@@ -1387,6 +1406,7 @@ static void ppp_setup(struct net_device *dev)
dev->tx_queue_len = 3;
dev->type = ARPHRD_PPP;
dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
+ dev->priv_destructor = ppp_dev_priv_destructor;
netif_keep_dst(dev);
}
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