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Date: Fri, 28 Jun 2019 12:51:53 +0900
From: Taehee Yoo <ap420073@...il.com>
To: Roopa Prabhu <roopa@...ulusnetworks.com>
Cc: David Miller <davem@...emloft.net>,
netdev <netdev@...r.kernel.org>,
Petr Machata <petrm@...lanox.com>
Subject: Re: [PATCH net v2] vxlan: do not destroy fdb if register_netdevice()
is failed
On Fri, 28 Jun 2019 at 03:33, Roopa Prabhu <roopa@...ulusnetworks.com> wrote:
>
> On Thu, Jun 27, 2019 at 7:50 AM Taehee Yoo <ap420073@...il.com> wrote:
> >
> > __vxlan_dev_create() destroys FDB using specific pointer which indicates
> > a fdb when error occurs.
> > But that pointer should not be used when register_netdevice() fails because
> > register_netdevice() internally destroys fdb when error occurs.
> >
> > This patch makes vxlan_fdb_create() to do not link fdb entry to vxlan dev
> > internally.
> > Instead, a new function vxlan_fdb_link() is added to link fdb to vxlan dev.
> >
> > vxlan_fdb_link() is called after calling register_netdevice().
> > This routine can avoid situation that ->ndo_uninit() destroys fdb entry
> > in error path of register_netdevice().
> > Hence, error path of __vxlan_dev_create() routine can have an opportunity
> > to destroy default fdb entry by hand.
> >
> > Test command
> > ip link add bonding_masters type vxlan id 0 group 239.1.1.1 \
> > dev enp0s9 dstport 4789
> >
> > Splat looks like:
> > [ 213.392816] kasan: GPF could be caused by NULL-ptr deref or user memory access
> > [ 213.401257] general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
> > [ 213.402178] CPU: 0 PID: 1414 Comm: ip Not tainted 5.2.0-rc5+ #256
> > [ 213.402178] RIP: 0010:vxlan_fdb_destroy+0x120/0x220 [vxlan]
> > [ 213.402178] Code: df 48 8b 2b 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 06 01 00 00 4c 8b 63 08 48 b8 00 00 00 00 00 fc d
> > [ 213.402178] RSP: 0018:ffff88810cb9f0a0 EFLAGS: 00010202
> > [ 213.402178] RAX: dffffc0000000000 RBX: ffff888101d4a8c8 RCX: 0000000000000000
> > [ 213.402178] RDX: 1bd5a00000000040 RSI: ffff888101d4a8c8 RDI: ffff888101d4a8d0
> > [ 213.402178] RBP: 0000000000000000 R08: fffffbfff22b72d9 R09: 0000000000000000
> > [ 213.402178] R10: 00000000ffffffef R11: 0000000000000000 R12: dead000000000200
> > [ 213.402178] R13: ffff88810cb9f1f8 R14: ffff88810efccda0 R15: ffff88810efccda0
> > [ 213.402178] FS: 00007f7f6621a0c0(0000) GS:ffff88811b000000(0000) knlGS:0000000000000000
> > [ 213.402178] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 213.402178] CR2: 000055746f0807d0 CR3: 00000001123e0000 CR4: 00000000001006f0
> > [ 213.402178] Call Trace:
> > [ 213.402178] __vxlan_dev_create+0x3a9/0x7d0 [vxlan]
> > [ 213.402178] ? vxlan_changelink+0x740/0x740 [vxlan]
> > [ 213.402178] ? rcu_read_unlock+0x60/0x60 [vxlan]
> > [ 213.402178] ? __kasan_kmalloc.constprop.3+0xa0/0xd0
> > [ 213.402178] vxlan_newlink+0x8d/0xc0 [vxlan]
> > [ 213.402178] ? __vxlan_dev_create+0x7d0/0x7d0 [vxlan]
> > [ 213.554119] ? __netlink_ns_capable+0xc3/0xf0
> > [ 213.554119] __rtnl_newlink+0xb75/0x1180
> > [ 213.554119] ? rtnl_link_unregister+0x230/0x230
> > [ ... ]
> >
> > Fixes: 0241b836732f ("vxlan: fix default fdb entry netlink notify ordering during netdev create")
> > Suggested-by: Roopa Prabhu <roopa@...ulusnetworks.com>
> > Signed-off-by: Taehee Yoo <ap420073@...il.com>
> > ---
> >
> > v1 -> v2 :
> > - Add a new function vxlan_fdb_link().
> > - Fix fdb entry leak.
> > - Update description.
> >
>
> thanks for v2!. a few comments inline below ...
>
Thank you for review!
> > drivers/net/vxlan.c | 27 +++++++++++++++++++--------
> > 1 file changed, 19 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
> > index 083f3f0bf37f..4066346d6f41 100644
> > --- a/drivers/net/vxlan.c
> > +++ b/drivers/net/vxlan.c
> > @@ -804,6 +804,14 @@ static struct vxlan_fdb *vxlan_fdb_alloc(struct vxlan_dev *vxlan,
> > return f;
> > }
> >
> > +static void vxlan_fdb_link(struct vxlan_dev *vxlan, const u8 *mac,
> > + __be32 src_vni, struct vxlan_fdb *f)
>
> I would prefer vxlan_fdb_insert or something along those lines.
>
> > +{
> > + ++vxlan->addrcnt;
> > + hlist_add_head_rcu(&f->hlist,
> > + vxlan_fdb_head(vxlan, mac, src_vni));
> > +}
> > +
> > static int vxlan_fdb_create(struct vxlan_dev *vxlan,
> > const u8 *mac, union vxlan_addr *ip,
> > __u16 state, __be16 port, __be32 src_vni,
> > @@ -829,10 +837,6 @@ static int vxlan_fdb_create(struct vxlan_dev *vxlan,
> > return rc;
> > }
> >
> > - ++vxlan->addrcnt;
> > - hlist_add_head_rcu(&f->hlist,
> > - vxlan_fdb_head(vxlan, mac, src_vni));
> > -
> > *fdb = f;
> >
> > return 0;
> > @@ -977,6 +981,7 @@ static int vxlan_fdb_update_create(struct vxlan_dev *vxlan,
> > if (rc < 0)
> > return rc;
> >
> > + vxlan_fdb_link(vxlan, mac, src_vni, f);
> > rc = vxlan_fdb_notify(vxlan, f, first_remote_rtnl(f), RTM_NEWNEIGH,
> > swdev_notify, extack);
> > if (rc)
> > @@ -3571,12 +3576,17 @@ static int __vxlan_dev_create(struct net *net, struct net_device *dev,
> > if (err)
> > goto errout;
> >
> > - /* notify default fdb entry */
> > if (f) {
> > + vxlan_fdb_link(vxlan, all_zeros_mac,
> > + vxlan->default_dst.remote_vni, f);
> > +
> > + /* notify default fdb entry */
> > err = vxlan_fdb_notify(vxlan, f, first_remote_rtnl(f),
> > RTM_NEWNEIGH, true, extack);
> > - if (err)
> > - goto errout;
> > + if (err) {
> > + vxlan_fdb_destroy(vxlan, f, false, false);
> > + goto unregister;
> > + }
> > }
> >
> > list_add(&vxlan->next, &vn->vxlan_list);
> > @@ -3588,7 +3598,8 @@ static int __vxlan_dev_create(struct net *net, struct net_device *dev,
> > * destroy the entry by hand here.
> > */
> > if (f)
> > - vxlan_fdb_destroy(vxlan, f, false, false);
> > + call_rcu(&f->rcu, vxlan_fdb_free);
>
> f is local to this function and not inserted at this point, so maybe
> we dont need to call_rcu here ?
>
I totally agree with your comments.
So, I will send a new patch.
Thank you!
> > +unregister:
> > if (unregister)
> > unregister_netdevice(dev);
> > return err;
> > --
> > 2.17.1
> >
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