Re: [PATCH mptcp-net 0/3] mptcp: fix memcg accounting for passive sockets

[Matthieu Baerts <matttbe@kernel.org>]

Hi Paolo,

On 07/11/2025 22:55, Paolo Abeni wrote:
> It turns out that the splat reported earlier is indeed due to an old
> bug/missing feature that hit hard on top of "mptcp: borrow forward 
> memory from subflow", as we can borrow accounted memory from a socket
> not doing any accounting;)
> 
> It should land upstream before the above mentioned commit, ence the
> 'net' target, but it could as well be net-next material.
> 
> I think there is still a racing window to produce the splat reported in
> #597: if a subflow receive data while the msk is locked, and before the
> memcg is initialized on such subflow, it will push the data into the msk
> becklog, and later borrow will again try to grab accounted memory from
> non accounting ssk.
> 
> I have a tentative fix for that one but it's quite ugly and I'll keep it
> separate from this series.

As discussed on IRC, it is fine to already apply this series.

Now in our tree, feat. for net-next, before "mptcp: cleanup fallback
data fin reception".

New patches for t/upstream:
- d4e154d9235e: net: factor-out _sk_charge() helper
  (Note: I'm going to change the RvB tags to Acked-by: non MPTCP change)
- c39f3876137b: mptcp: factor-out cgroup data inherit helper
- ce0882b539e6: mptcp: fix memcg accounting for passive sockets
- Results: 83290f9ea1dc..8ecdad1578d9 (export)

Tests are now in progress:

- export:
https://github.com/multipath-tcp/mptcp_net-next/commit/ddd5885869f67ae638bb3c8db14dfc80a1fe2bfd/checks

Cheers,
Matt
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