Subject: Re: memory leak in internal_dev_create

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Thu, 8 Aug 2019 21:45:17 -0300

On Wed, Aug 07, 2019 at 01:32:40PM -0700, Pravin Shelar wrote:
> On Tue, Aug 6, 2019 at 5:00 AM Hillf Danton <[email-masked]> wrote:
> >
> >
> > On Tue, 06 Aug 2019 01:58:05 -0700
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> 
> ...
> > > BUG: memory leak
> > > unreferenced object 0xffff8881228ca500 (size 128):
> > >    comm "syz-executor032", pid 7015, jiffies 4294944622 (age 7.880s)
> > >    hex dump (first 32 bytes):
> > >      00 f0 27 18 81 88 ff ff 80 ac 8c 22 81 88 ff ff  ..'........"....
> > >      40 b7 23 17 81 88 ff ff 00 00 00 00 00 00 00 00  @.#.............
> > >    backtrace:
> > >      [<000000000eb78212>] kmemleak_alloc_recursive  include/linux/kmemleak.h:43 [inline]
> > >      [<000000000eb78212>] slab_post_alloc_hook mm/slab.h:522 [inline]
> > >      [<000000000eb78212>] slab_alloc mm/slab.c:3319 [inline]
> > >      [<000000000eb78212>] kmem_cache_alloc_trace+0x145/0x2c0 mm/slab.c:3548
> > >      [<00000000006ea6c6>] kmalloc include/linux/slab.h:552 [inline]
> > >      [<00000000006ea6c6>] kzalloc include/linux/slab.h:748 [inline]
> > >      [<00000000006ea6c6>] ovs_vport_alloc+0x37/0xf0  net/openvswitch/vport.c:130
> > >      [<00000000f9a04a7d>] internal_dev_create+0x24/0x1d0  net/openvswitch/vport-internal_dev.c:164
> > >      [<0000000056ee7c13>] ovs_vport_add+0x81/0x190  net/openvswitch/vport.c:199
> > >      [<000000005434efc7>] new_vport+0x19/0x80 net/openvswitch/datapath.c:194
> > >      [<00000000b7b253f1>] ovs_dp_cmd_new+0x22f/0x410  net/openvswitch/datapath.c:1614
> > >      [<00000000e0988518>] genl_family_rcv_msg+0x2ab/0x5b0  net/netlink/genetlink.c:629
> > >      [<00000000d0cc9347>] genl_rcv_msg+0x54/0x9c net/netlink/genetlink.c:654
> > >      [<000000006694b647>] netlink_rcv_skb+0x61/0x170  net/netlink/af_netlink.c:2477
> > >      [<0000000088381f37>] genl_rcv+0x29/0x40 net/netlink/genetlink.c:665
> > >      [<00000000dad42a47>] netlink_unicast_kernel  net/netlink/af_netlink.c:1302 [inline]
> > >      [<00000000dad42a47>] netlink_unicast+0x1ec/0x2d0  net/netlink/af_netlink.c:1328
> > >      [<0000000067e6b079>] netlink_sendmsg+0x270/0x480  net/netlink/af_netlink.c:1917
> > >      [<00000000aab08a47>] sock_sendmsg_nosec net/socket.c:637 [inline]
> > >      [<00000000aab08a47>] sock_sendmsg+0x54/0x70 net/socket.c:657
> > >      [<000000004cb7c11d>] ___sys_sendmsg+0x393/0x3c0 net/socket.c:2311
> > >      [<00000000c4901c63>] __sys_sendmsg+0x80/0xf0 net/socket.c:2356
> > >      [<00000000c10abb2d>] __do_sys_sendmsg net/socket.c:2365 [inline]
> > >      [<00000000c10abb2d>] __se_sys_sendmsg net/socket.c:2363 [inline]
> > >      [<00000000c10abb2d>] __x64_sys_sendmsg+0x23/0x30 net/socket.c:2363
> >
> >
> > Always free vport manually unless register_netdevice() succeeds.
> >
> > --- a/net/openvswitch/vport-internal_dev.c
> > +++ b/net/openvswitch/vport-internal_dev.c
> > @@ -137,7 +137,7 @@ static void do_setup(struct net_device *
> >         netdev->priv_flags |= IFF_LIVE_ADDR_CHANGE | IFF_OPENVSWITCH |
> >                               IFF_NO_QUEUE;
> >         netdev->needs_free_netdev = true;
> > -       netdev->priv_destructor = internal_dev_destructor;
> > +       netdev->priv_destructor = NULL;
> >         netdev->ethtool_ops = &internal_dev_ethtool_ops;
> >         netdev->rtnl_link_ops = &internal_dev_link_ops;
> >
> > @@ -159,7 +159,6 @@ static struct vport *internal_dev_create
> >         struct internal_dev *internal_dev;
> >         struct net_device *dev;
> >         int err;
> > -       bool free_vport = true;
> >
> >         vport = ovs_vport_alloc(0, &ovs_internal_vport_ops, parms);
> >         if (IS_ERR(vport)) {
> > @@ -190,10 +189,9 @@ static struct vport *internal_dev_create
> >
> >         rtnl_lock();
> >         err = register_netdevice(vport->dev);
> > -       if (err) {
> > -               free_vport = false;
> > +       if (err)
> >                 goto error_unlock;
> > -       }
> > +       vport->dev->priv_destructor = internal_dev_destructor;
> >
> I am not sure why have you moved this assignment out of do_setup().
> 
> Otherwise patch looks good to me.
> 
> Thanks.

Seems it's to avoid re-introducing the issue that was fixed by:

commit 309b66970ee2abf721ecd0876a48940fa0b99a35
Author: Taehee Yoo <[email-masked]>
Date:   Sun Jun 9 23:26:21 2019 +0900

    net: openvswitch: do not free vport if register_netdevice() is failed.

A Fixes: 309b66970ee2a  is welcomed then.

> >         dev_set_promiscuity(vport->dev, 1);
> >         rtnl_unlock();
> > @@ -207,8 +205,7 @@ error_unlock:
> >  error_free_netdev:
> >         free_netdev(dev);
> >  error_free_vport:
> > -       if (free_vport)
> > -               ovs_vport_free(vport);
> > +       ovs_vport_free(vport);
> >  error:
> >         return ERR_PTR(err);
> >  }
> > --
> >
>