netdev - Re: [PATCH bpf v1 2/2] selftests/bpf: Test using cgroup storage in a tail call callee program

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Message-ID: <CAMB2axOBJ-BceMjGwT4=E6h+Jh2ba70s70fFJvL4u9Bq389UXA@mail.gmail.com>
Date: Mon, 1 Dec 2025 21:44:16 -0800
From: Amery Hung <ameryhung@...il.com>
To: Eduard Zingerman <eddyz87@...il.com>
Cc: bpf@...r.kernel.org, netdev@...r.kernel.org, alexei.starovoitov@...il.com, 
	andrii@...nel.org, daniel@...earbox.net, martin.lau@...nel.org, 
	kernel-team@...a.com
Subject: Re: [PATCH bpf v1 2/2] selftests/bpf: Test using cgroup storage in a
 tail call callee program

On Mon, Dec 1, 2025 at 5:08 PM Eduard Zingerman <eddyz87@...il.com> wrote:
>
> On Mon, 2025-12-01 at 16:18 -0800, Amery Hung wrote:
> > Check that a BPF program that uses cgroup storage cannot be added to
> > a program array map.
> >
> > Signed-off-by: Amery Hung <ameryhung@...il.com>
> > ---
>
> Hi Amery,
>
> Mabye I'm making some silly systematic mistake, but when I pick this
> test w/o picking patch #1 the test still passes.
> I'm at ff34657aa72a ("bpf: optimize bpf_map_update_elem() for map-in-map types").
> Inserting some printk shows that -EINVAL is propagated for map update
> from kernel/bpf/core.c:__bpf_prog_map_compatible() line 2406
> (`ret = map->owner->storage_cookie[i] == cookie || !cookie;`).

Thanks for the double check! I simplified the selftest too much and
introduced the false negative.

There should be another program using the prog array and the same
cgroup storage in the first place so that the check here passes.

I will fix and resubmit.

>
> [...]