Re: [RFC PATCH 0/1] net: socket: centralize netns refcounting

[Kuniyuki Iwashima]

From: Enzo Matsumiya <ematsumiya@xxxxxxx>
Date: Fri, 16 May 2025 19:09:18 -0300
> Hi,
> 
> I came up with this patch to centralize netns refcounting on kernel sockets,
> because `sk_net_refcnt = !kern' is not enough anymore.
> 
> The idea is simply to remove the responsibility of a module outside of net/
> to have to deal with sockets internals (cf. sk_net_refcnt_upgrade()).
> 
> It adds an anonymous enum (just for named values) SOCK_NETNS_REFCNT_* that
> can be passed to __sock_create() and sk_alloc() through the @kern arg.
> (this was much easier and shorter than e.g. adding another arg)
> 
> A sock_create_netns() wrapper is added, for callers who need such refcounting
> (e.g. current callers of sk_net_refcnt_upgrade()).
> 
> And then, the core change is quite simple in sk_alloc() -- sk_net_refcnt is
> set only if it's a user socket, or
> (@kern == SOCK_NETNS_REFCNT_KERN_ANY && @net != inet_net).
> 
> I have the patches that modifies current users of sk_net_refcnt_upgrade() to
> create their sockets with sock_create_netns(), if anyone wants to test or
> this gets merged.
> 
> I could confirm this works only on cifs, though, by using Kuniyuki's reproducer
> in [0], which is quite reliable.  Unfortunately, I don't know enough about the
> other modules and/or how to trigger this same bug on those, but I'll be happy
> to test it if I can get instructions.
> 

I was waiting for b013b817f32f to land on net-next to respin
this series [0] as propised in [1].

[0]: https://lore.kernel.org/netdev/20241213092152.14057-1-kuniyu@xxxxxxxxxx/#t
[1]: https://lore.kernel.org/lkml/20250409190031.38942-1-kuniyu@xxxxxxxxxx/

So, let me respin it.

FWIW, I posted the most identical patch before the series.
https://lore.kernel.org/netdev/20240227011041.97375-4-kuniyu@xxxxxxxxxx/