netdev - Re: [linux-next:master] [net] d288a162dd: canonical

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Date:   Wed, 19 Apr 2023 08:59:16 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     David Ahern <dsahern@...nel.org>
Cc:     kernel test robot <oliver.sang@...el.com>,
        Wangyang Guo <wangyang.guo@...el.com>,
        Jakub Kicinski <kuba@...nel.org>, oe-lkp@...ts.linux.dev,
        lkp@...el.com, Linux Memory Management List <linux-mm@...ck.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        steffen.klassert@...unet.com
Subject: Re: [linux-next:master] [net] d288a162dd: canonical_address#:#[##]

On Tue, Apr 18, 2023 at 02:43:02PM -0600, David Ahern wrote:
> On 4/18/23 10:41 AM, Leon Romanovsky wrote:
> > Hi,
> > 
> > I came to the following diff which eliminates the kernel panics,
> > unfortunately I can explain only second hunk, but first is required
> > too.
> > 
> > diff --git a/net/core/dst.c b/net/core/dst.c
> > index 3247e84045ca..750c8edfe29a 100644
> > --- a/net/core/dst.c
> > +++ b/net/core/dst.c
> > @@ -72,6 +72,8 @@ void dst_init(struct dst_entry *dst, struct dst_ops *ops,
> >         dst->flags = flags;
> >         if (!(flags & DST_NOCOUNT))
> >                 dst_entries_add(ops, 1);
> > +
> > +       INIT_LIST_HEAD(&dst->rt_uncached);
> 
> d288a162dd1c73507da582966f17dd226e34a0c0 moved rt_uncached from rt6_info
> and rtable to dst_entry. Only ipv4 and ipv6 usages initialize it. Since
> it is now in dst_entry, dst_init is the better place so it can be
> removed from rt_dst_alloc and rt6_info_init.

This is why I placed it there, but the rt_uncached list is initialized
in xfrm6 right before first call to rt6_uncached_list_add().

   70 static int xfrm6_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
   71                           const struct flowi *fl)
   72 {
...
   92         INIT_LIST_HEAD(&xdst->u.rt6.dst.rt_uncached);
   93         rt6_uncached_list_add(&xdst->u.rt6);

My silly explanation is that xfrm6_dst_destroy() can be called before xfrm6_fill_dst().

Thanks

>