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Message-ID: <20151223230328.GA967745@devbig337.prn1.facebook.com>
Date: Wed, 23 Dec 2015 15:03:28 -0800
From: Calvin Owens <calvinowens@...com>
To: Eric Dumazet <eric.dumazet@...il.com>
CC: <davem@...emloft.net>, <shm@...ulusnetworks.com>,
<izumi.taku@...fujitsu.com>, <linville@...driver.com>,
<dsa@...ulusnetworks.com>, <netdev@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <kernel-team@...com>,
Cong Wang <amwang@...hat.com>
Subject: Re: [PATCH] netconsole: Initialize after all core networking drivers
On Thursday 12/17 at 17:46 -0800, Calvin Owens wrote:
> On Thursday 12/17 at 17:08 -0800, Eric Dumazet wrote:
> > On Thu, 2015-12-17 at 15:52 -0800, Calvin Owens wrote:
> > > With built-in netconsole and IXGBE, configuring netconsole via the kernel
> > > cmdline results in the following panic at boot:
> > >
> > > netpoll: netconsole: device eth0 not up yet, forcing it
> > > usb 2-1: new high-speed USB device number 2 using ehci-pci
> > > ixgbe 0000:03:00.0: registered PHC device on eth0
> > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000810
> > > <snip>
> > > Call Trace:
> > > [<ffffffff81578661>] ? vxlan_get_rx_port+0x41/0xa0
> > > [<ffffffff81586828>] ixgbe_open+0x4e8/0x540
> > > [<ffffffff8168045c>] __dev_open+0xac/0x120
> > > [<ffffffff81680506>] dev_open+0x36/0x70
> > > [<ffffffff8169abec>] netpoll_setup+0x23c/0x300
> > > [<ffffffff8169a66a>] ? netpoll_parse_options+0x19a/0x200
> > > [<ffffffff81d797a8>] ? option_setup+0x1f/0x1f
> > > [<ffffffff81d79882>] init_netconsole+0xda/0x262
> > > [<ffffffff81d797a8>] ? option_setup+0x1f/0x1f
> > > [<ffffffff810003a8>] do_one_initcall+0x88/0x1b0
> > > [<ffffffff81d31144>] kernel_init_freeable+0x14a/0x1e3
> > > [<ffffffff81d308f1>] ? do_early_param+0x8c/0x8c
> > > [<ffffffff81778610>] ? rest_init+0x80/0x80
> > > [<ffffffff8177861e>] kernel_init+0xe/0xe0
> > > [<ffffffff8177dc5f>] ret_from_fork+0x3f/0x70
> > > [<ffffffff81778610>] ? rest_init+0x80/0x80
> > >
> > > This happens because IXGBE assumes that vxlan has already been initialized.
> > > The cleanest way to fix this is to just initialize netconsole after all the
> > > other core networking stuff has completed.
> > >
> > > Signed-off-by: Calvin Owens <calvinowens@...com>
> > > ---
> > > drivers/net/Makefile | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/net/Makefile b/drivers/net/Makefile
> > > index 900b0c5..31557d0 100644
> > > --- a/drivers/net/Makefile
> > > +++ b/drivers/net/Makefile
> > > @@ -15,7 +15,6 @@ obj-$(CONFIG_MACVTAP) += macvtap.o
> > > obj-$(CONFIG_MII) += mii.o
> > > obj-$(CONFIG_MDIO) += mdio.o
> > > obj-$(CONFIG_NET) += Space.o loopback.o
> > > -obj-$(CONFIG_NETCONSOLE) += netconsole.o
> > > obj-$(CONFIG_PHYLIB) += phy/
> > > obj-$(CONFIG_RIONET) += rionet.o
> > > obj-$(CONFIG_NET_TEAM) += team/
> > > @@ -26,6 +25,7 @@ obj-$(CONFIG_VXLAN) += vxlan.o
> > > obj-$(CONFIG_GENEVE) += geneve.o
> > > obj-$(CONFIG_NLMON) += nlmon.o
> > > obj-$(CONFIG_NET_VRF) += vrf.o
> > > +obj-$(CONFIG_NETCONSOLE) += netconsole.o
> > >
> > > #
> > > # Networking Drivers
> >
> >
> > Looks odd to rely on link order, but we might already rely on this...
> >
> > Have you considered using device_initcall() instead of late_initcall()
> > in vxlan ?
>
> I'll look.
So this does work, but commit 7332a13b038be05c explicitly changed it to
late_initcall() because of dependencies on IPv6:
When vxlan is compiled as builtin, its init code
runs before IPv6 init, this could cause problems
if we create IPv6 socket in the latter patch.
So I guess something like the following patch is needed to go that
route? It's ugly, IMHO the Makefile patch is cleaner...
Stephen / Cong, what do you think?
> As-is though, I think a similar problem would happen if you
> tried to use a virtio_net device with netconsole= cmdline (although that
> is admittedly a bizarre use case). The Makefile patch seemed like the
> best way to ensure this can't recur elsewhere.
I misunderstood this, it works fine as is.
---8<---
From: Calvin Owens <calvinowens@...com>
Subject: [PATCH] vxlan: Properly depend on ipv6 and revert to module_init()
Commit 7332a13b038be05c ("vxlan: defer vxlan init as late as possible")
changed vxlan to use late_initcall(), because vxlan relies on ipv6 being
loaded when a new device is opened.
This causes netconsole to panic at boot when configured via the kernel
cmdline on an IXGBE NIC, because ixgbe_open() assumes that vxlan has
already been initialized:
netpoll: netconsole: device eth0 not up yet, forcing it
ixgbe 0000:03:00.0: registered PHC device on eth0
BUG: unable to handle kernel NULL pointer dereference at 0000000000000810
<snip>
Call Trace:
[<ffffffff81578661>] ? vxlan_get_rx_port+0x41/0xa0
[<ffffffff81586828>] ixgbe_open+0x4e8/0x540
[<ffffffff8168045c>] __dev_open+0xac/0x120
[<ffffffff81680506>] dev_open+0x36/0x70
[<ffffffff8169abec>] netpoll_setup+0x23c/0x300
[<ffffffff8169a66a>] ? netpoll_parse_options+0x19a/0x200
[<ffffffff81d797a8>] ? option_setup+0x1f/0x1f
[<ffffffff81d79882>] init_netconsole+0xda/0x262
[<ffffffff81d797a8>] ? option_setup+0x1f/0x1f
[<ffffffff810003a8>] do_one_initcall+0x88/0x1b0
[<ffffffff81d31144>] kernel_init_freeable+0x14a/0x1e3
[<ffffffff81d308f1>] ? do_early_param+0x8c/0x8c
[<ffffffff81778610>] ? rest_init+0x80/0x80
[<ffffffff8177861e>] kernel_init+0xe/0xe0
[<ffffffff8177dc5f>] ret_from_fork+0x3f/0x70
[<ffffffff81778610>] ? rest_init+0x80/0x80
This patch addresses the issue cited in 7332a13b038be05c by making vxlan
actually check if ipv6 is loaded, and reverts it to module_init() so
that it becomes device_initcall() when built-in, eliminating the
netconsole issue.
The ipv6 module is permanent, so there's no need to actually do the
usual module_get/module_put dance: once we find it loaded, we can just
assume that it always will be.
AFAICS, nothing actually ends up calling vxlan_open() during initcalls,
so in the (IPV6=y && VXLAN=y) case we can't end up there before ipv6 has
initialized.
Signed-off-by: Calvin Owens <calvinowens@...com>
---
drivers/net/vxlan.c | 35 ++++++++++++++++++++++++++++++++++-
1 file changed, 34 insertions(+), 1 deletion(-)
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index ba363ce..e3061b7 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -158,6 +158,36 @@ static int vxlan_nla_put_addr(struct sk_buff *skb, int attr,
return nla_put_in_addr(skb, attr, ip->sin.sin_addr.s_addr);
}
+#if IS_MODULE(CONFIG_IPV6)
+MODULE_SOFTDEP("pre: ipv6");
+
+/*
+ * IPv6 is permanent, so once we find it loaded we can just assume it always
+ * will be, and avoid walking the module_list every time we open a new vxlan
+ * device.
+ */
+static bool vxlan_ipv6_is_loaded(void)
+{
+ static bool ipv6_loaded = false;
+
+ if (!ipv6_loaded) {
+ mutex_lock(&module_mutex);
+ ipv6_loaded = !!find_module("ipv6");
+ mutex_unlock(&module_mutex);
+ }
+
+ return ipv6_loaded;
+}
+
+#elif IS_BUILTIN(CONFIG_IPV6)
+
+static bool vxlan_ipv6_is_loaded(void)
+{
+ return true;
+}
+
+#endif /* IS_{MODULE,BUILTIN}(CONFIG_IPV6) */
+
#else /* !CONFIG_IPV6 */
static inline
@@ -2628,6 +2658,9 @@ static struct socket *vxlan_create_sock(struct net *net, bool ipv6,
memset(&udp_conf, 0, sizeof(udp_conf));
if (ipv6) {
+ if (!vxlan_ipv6_is_loaded())
+ return ERR_PTR(-EAFNOSUPPORT);
+
udp_conf.family = AF_INET6;
udp_conf.use_udp6_rx_checksums =
!(flags & VXLAN_F_UDP_ZERO_CSUM6_RX);
@@ -3259,7 +3292,7 @@ out1:
destroy_workqueue(vxlan_wq);
return rc;
}
-late_initcall(vxlan_init_module);
+module_init(vxlan_init_module);
static void __exit vxlan_cleanup_module(void)
{
--
2.5.0
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