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

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Message-ID: <CANn89i+bZY8vseiWQb6gye=YayDzgrMeyrk1k5Ex_ux-NcMRnw@mail.gmail.com>
Date: Mon, 23 Sep 2024 22:14:09 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Mitchell Augustin <mitchell.augustin@...onical.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

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);