linux-kernel - Re: Namespaced network devices not cleaned up properly after execution of pmtu.sh kernel selftest

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Message-ID: <CAHTA-uZK_U8_0t85Z3xdJJ-mih7WovgXzXkT1k2VygaXP48AaQ@mail.gmail.com>
Date: Tue, 24 Sep 2024 11:21:00 -0500
From: Mitchell Augustin <mitchell.augustin@...onical.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
	Paolo Abeni <pabeni@...hat.com>, Jiri Pirko <jiri@...nulli.us>, 
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Lorenzo Bianconi <lorenzo@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Jacob Martin <jacob.martin@...onical.com>, dann frazier <dann.frazier@...onical.com>
Subject: Re: Namespaced network devices not cleaned up properly after
 execution of pmtu.sh kernel selftest

> As I said before, we were aware of this issue, well before your report.

Yes, sorry - to clarify, I wasn't commenting on the state of the bug
itself, just asking whether my reproducer is helpful in exposing it
more easily/reliably and on more systems than other known methods, per
Jakub's original request.

In any case, thank you for the additional context on the bug itself though.

-Mitchell Augustin

On Mon, Sep 23, 2024 at 3:14 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Mon, Sep 23, 2024 at 10:01 PM Mitchell Augustin
> <mitchell.augustin@...onical.com> wrote:
> >
> > Hi!
> >
> > I'm wondering if anyone has taken a look at my reproducer yet. I'd
> > love to know if it has helped any of you reproduce the bug more
> > easily.
> >
> > Patch w/ reproducer:
> > https://lore.kernel.org/all/20240916191857.1082092-1-mitchell.augustin@canonical.com/
> >
>
> As I said before, we were aware of this issue, well before your report.
>
> We have no efficient fix yet.
> https://lore.kernel.org/netdev/202405311808.vqBTwxEf-lkp@intel.com/T/
>
> You can disable dst_cache, this should remove the issue.
>
> diff --git a/net/core/dst_cache.c b/net/core/dst_cache.c
> index 70c634b9e7b02300188582a1634d5977838db132..53351ff58b35dbee37ff587f7ef8f72580d9e116
> 100644
> --- a/net/core/dst_cache.c
> +++ b/net/core/dst_cache.c
> @@ -142,12 +142,7 @@ EXPORT_SYMBOL_GPL(dst_cache_get_ip6);
>
>  int dst_cache_init(struct dst_cache *dst_cache, gfp_t gfp)
>  {
> -       dst_cache->cache = alloc_percpu_gfp(struct dst_cache_pcpu,
> -                                           gfp | __GFP_ZERO);
> -       if (!dst_cache->cache)
> -               return -ENOMEM;
> -
> -       dst_cache_reset(dst_cache);
> +       dst_cache->cache = NULL;
>         return 0;
>  }
>  EXPORT_SYMBOL_GPL(dst_cache_init);



-- 
Mitchell Augustin
Software Engineer - Ubuntu Partner Engineering