linux-kernel - Re: [PATCH v3 bpf-next 0/4] Introduce bpf_cgroup_read

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Message-ID: <CAPhsuW7JAgXUObzkMAs_B=O09uHfhkgSuFV5nvUJbsv=Fh8JyA@mail.gmail.com>
Date: Thu, 26 Jun 2025 21:04:34 -0700
From: Song Liu <song@...nel.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Christian Brauner <brauner@...nel.org>, Kernel Team <kernel-team@...a.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Eduard <eddyz87@...il.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
	KP Singh <kpsingh@...nel.org>, Matt Bobrowski <mattbobrowski@...gle.com>, 
	Amir Goldstein <amir73il@...il.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Tejun Heo <tj@...nel.org>, Daan De Meyer <daan.j.demeyer@...il.com>, bpf <bpf@...r.kernel.org>, 
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	LSM List <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v3 bpf-next 0/4] Introduce bpf_cgroup_read_xattr

On Thu, Jun 26, 2025 at 7:14 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
[...]
> ./test_progs -t lsm_cgroup
> Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED
> ./test_progs -t lsm_cgroup
> Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED
> ./test_progs -t cgroup_xattr
> Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED
> ./test_progs -t lsm_cgroup
> test_lsm_cgroup_functional:PASS:bind(ETH_P_ALL) 0 nsec
> (network_helpers.c:121: errno: Cannot assign requested address) Failed
> to bind socket
> test_lsm_cgroup_functional:FAIL:start_server unexpected start_server:
> actual -1 < expected 0
> (network_helpers.c:360: errno: Bad file descriptor) getsockopt(SOL_PROTOCOL)
> test_lsm_cgroup_functional:FAIL:connect_to_fd unexpected
> connect_to_fd: actual -1 < expected 0
> test_lsm_cgroup_functional:FAIL:accept unexpected accept: actual -1 < expected 0
> test_lsm_cgroup_functional:FAIL:getsockopt unexpected getsockopt:
> actual -1 < expected 0
> test_lsm_cgroup_functional:FAIL:sk_priority unexpected sk_priority:
> actual 0 != expected 234
> ...
> Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED
>
>
> Song,
> Please follow up with the fix for selftest.
> It will be in bpf-next only.

The issue is because cgroup_xattr calls "ip link set dev lo up"
in setup, and calls "ip link set dev lo down" in cleanup. Most
other tests only call "ip link set dev lo up". IOW, it appears to
me that cgroup_xattr is doing the cleanup properly. To fix this,
we can either remove "dev lo down" from cgroup_xattr, or add
"dev lo up" to lsm_cgroups. Do you have any preference one
way or another?

Thanks,
Song