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

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Message-ID: <20250701-zipfel-sachlage-c494f4e0df91@brauner>
Date: Tue, 1 Jul 2025 10:32:29 +0200
From: Christian Brauner <brauner@...nel.org>
To: Song Liu <songliubraving@...a.com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, 
	Song Liu <song@...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 Fri, Jun 27, 2025 at 04:20:58PM +0000, Song Liu wrote:
> 
> 
> > On Jun 27, 2025, at 8:59 AM, Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
> > 
> > On Thu, Jun 26, 2025 at 9:04 PM Song Liu <song@...nel.org> wrote:
> >> 
> >> 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?
> > 
> > It messes with "lo" without switching netns? Ouch.
> 
> Ah, I see the problem now. 
> 
> > Not sure what tests you copied that code from,
> > but all "ip" commands, ping_group_range, and sockets
> > don't need to be in the test. Instead of triggering
> > progs through lsm/socket_connect hook can't you use
> > a simple hook like lsm/bpf or lsm/file_open that doesn't require
> > networking setup ?
> 
> Yeah, let me fix the test with a different hook. 

Where's the patch?