linux-kernel - Re: [PATCH net-next 0/6] mptcp: misc. features for v6.18

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Message-ID: <834238b4-3549-4062-a29b-bf9c5aefa30f@kernel.org>
Date: Tue, 2 Sep 2025 16:51:47 +0200
From: Matthieu Baerts <matttbe@...nel.org>
To: Jakub Kicinski <kuba@...nel.org>
Cc: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>,
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, Jonathan Corbet <corbet@....net>,
 Shuah Khan <shuah@...nel.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Eric Biggers <ebiggers@...nel.org>,
 Christoph Paasch <cpaasch@...nai.com>, Gang Yan <yangang@...inos.cn>
Subject: Re: [PATCH net-next 0/6] mptcp: misc. features for v6.18

Hi Jakub,

On 02/09/2025 16:26, Jakub Kicinski wrote:
> On Mon, 01 Sep 2025 11:39:09 +0200 Matthieu Baerts (NGI0) wrote:
>> This series contains 4 independent new features:
>>
>> - Patch 1: use HMAC-SHA256 library instead of open-coded HMAC.
>>
>> - Patches 2-3: make ADD_ADDR retransmission timeout adaptive + simplify
>>   selftests.
>>
>> - Patch 4: selftests: check for unexpected fallback counter increments.
>>
>> - Patches 5-6: record subflows in RPS table, for aRFS support.
> 
> I don't see why, but kmemleak started to hit this with the join test
> 2 branches ago :\ Have you seen any kmemleak issues on your side?
> We also see occasional leaked skb in driver tests which makes no sense.
> 
> unreferenced object 0xffff8880029d3340 (size 3016):
>   comm "softirq", pid 0, jiffies 4297316940
>   hex dump (first 32 bytes):
>     0a 00 01 02 0a 00 01 01 00 00 00 00 9e b8 7d 27  ..............}'
>     0a 00 07 41 00 00 00 00 00 00 00 00 00 00 00 00  ...A............
>   backtrace (crc 3653d88c):
>     kmem_cache_alloc_noprof+0x284/0x330
>     sk_prot_alloc.constprop.0+0x4e/0x1b0
>     sk_clone_lock+0x4b/0x10d0
>     mptcp_sk_clone_init+0x2e/0x10d0
>     subflow_syn_recv_sock+0x9d1/0x1680
>     tcp_check_req+0x3a4/0x1910
>     tcp_v4_rcv+0x1004/0x30a0
>     ip_protocol_deliver_rcu+0x82/0x350
>     ip_local_deliver_finish+0x35d/0x620
>     ip_local_deliver+0x19c/0x470
>     ip_rcv+0xc2/0x370
>     __netif_receive_skb_one_core+0x108/0x180
>     process_backlog+0x3c1/0x13e0
>     __napi_poll.constprop.0+0x9f/0x460
>     net_rx_action+0x54f/0xda0
>     handle_softirqs+0x215/0x610

Thank you for this notification!

No, I didn't notice that on our side. For KMemLeak, now I'm waiting 5
seconds, then I force the scan, and check for issues once. On NIPA, I
see that there are still 2 scans + cat, and apparently, the issue was
always visible during the 2nd scan:

https://netdev-3.bots.linux.dev/vmksft-mptcp-dbg/results/279881/1-mptcp-join-sh/stdout

https://netdev-3.bots.linux.dev/vmksft-mptcp-dbg/results/280062/1-mptcp-join-sh/stdout

It is unclear why a second scan is needed and only the second one caught
something. Was it the same with the strange issues you mentioned in
driver tests? Do you think I should re-add the second scan + cat?

When looking at the modifications of this series, it is unclear what
could cause that.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.