netdev - Re: [net PATCH 1/2] net: ipv6: fib: flush exceptions when purging route

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Date:   Thu, 7 Jan 2021 12:04:23 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Ahern <dsahern@...il.com>,
        Sean Tranchetti <stranche@...cinc.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        subashab@...earurora.org,
        Sean Tranchetti <stranche@...eaurora.org>,
        Wei Wang <weiwan@...gle.com>
Subject: Re: [net PATCH 1/2] net: ipv6: fib: flush exceptions when purging
 route

On Wed, 6 Jan 2021 09:55:09 -0700 David Ahern wrote:
> On 1/5/21 5:22 PM, Sean Tranchetti wrote:
> > From: Sean Tranchetti <stranche@...eaurora.org>
> > 
> > Route removal is handled by two code paths. The main removal path is via
> > fib6_del_route() which will handle purging any PMTU exceptions from the
> > cache, removing all per-cpu copies of the DST entry used by the route, and
> > releasing the fib6_info struct.
> > 
> > The second removal location is during fib6_add_rt2node() during a route
> > replacement operation. This path also calls fib6_purge_rt() to handle
> > cleaning up the per-cpu copies of the DST entries and releasing the
> > fib6_info associated with the older route, but it does not flush any PMTU
> > exceptions that the older route had. Since the older route is removed from
> > the tree during the replacement, we lose any way of accessing it again.
> > 
> > As these lingering DSTs and the fib6_info struct are holding references to
> > the underlying netdevice struct as well, unregistering that device from the
> > kernel can never complete.
> 
> I think the right fixes tag is:
> 
> Fixes: 2b760fcf5cfb3 ("ipv6: hook up exception table to store dst cache")
> 
> cc'ed author of that patch.
> 
> > Signed-off-by: Sean Tranchetti <stranche@...eaurora.org>
>
> Reviewed-by: David Ahern <dsahern@...nel.org>

Applied, thanks!