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: <20250401183625.66095-1-kuniyu@amazon.com>
Date: Tue, 1 Apr 2025 11:35:41 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <willemdebruijn.kernel@...il.com>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <edumazet@...gle.com>,
	<horms@...nel.org>, <kuba@...nel.org>, <kuni1840@...il.com>,
	<kuniyu@...zon.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.

From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Date: Mon, 31 Mar 2025 21:15:24 -0400
> 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.

Yes, and we need to query rmem_alloc via netlink.

Also, I haven't investigated, but I saw a weird timeout, when the usage
stuck at 523914, which is smaller than INT_MAX >> PAGE_SHIFT.

Probably the test needs to check sockets' rmem_alloc to be accurate.

I'll drop the test for now and follow up in net-next.

Thanks!