netdev - Re: [PATCH v4 net 0/3] udp: Fix two integer overflows when sk->sk_rcvbuf is close to INT

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Message-ID: <67eb3e2c92fb9_395352294e1@willemb.c.googlers.com.notmuch>
Date: Mon, 31 Mar 2025 21:15:24 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jakub Kicinski <kuba@...nel.org>, 
 Kuniyuki Iwashima <kuniyu@...zon.com>, 
 willemdebruijn.kernel@...il.com
Cc: davem@...emloft.net, 
 dsahern@...nel.org, 
 edumazet@...gle.com, 
 horms@...nel.org, 
 kuni1840@...il.com, 
 netdev@...r.kernel.org, 
 pabeni@...hat.com
Subject: Re: [PATCH v4 net 0/3] udp: Fix two integer overflows when
 sk->sk_rcvbuf is close to INT_MAX.

Jakub Kicinski wrote:
> On Mon, 31 Mar 2025 13:31:47 -0700 Kuniyuki Iwashima wrote:
> > > > Please do test locally if you can.  
> > > 
> > > Sure, will try the same tests with CI.  
> > 
> > Is there a way to tell NIPA to run a test in a dedicated VM ?
> > 
> > I see some tests succeed when executed solely but fail when
> > executed with
> > 
> >   make -C tools/testing/selftests/ TARGETS=net run_tests
> > 
> > When combined with other tests, assuming that the global UDP usage
> > will soon drop to 0 is not always easy... so it's defeating the
> > purpose but I'd drop the test in v5 not to make CI unhappy.
> 
> Can we account for some level of system noise? Or try to dump all 
> the sockets and count the "accounted for" in-use memory?
> 
> We can do various things in NIPA, but I'm not sure if it's okay 
> for tests inside net/ should require a completely idle system.
> If we want a completely idle system maybe user-mode Linux + kunit
> is a better direction?
> 
> Willem, WDYT?

The number of tests depending on global variables like
proto_memory_allocated is thankfully low.

kselftest/runner.sh runs RUN_IN_NETNS tests in parallel. That sounds
the case here. Perhaps we can add a test option to force running
without concurrent other tests?

Otherwise, the specific test drops usage from MAX to 0. And verifies
to reach MAX before exiting its loop.

Other concurrent tests are unlikely to spike very high. It might just
be sufficient to relax that ASSERT to something a bit higher than 0,
but a far cry from INT_MAX, to mean "clearly no longer stressed".