[PATCH v3 bpf-next 0/4] Introduce bpf_cgroup_read_xattr

[Christian Brauner]

On Tue, Jul 01, 2025 at 09:23:30AM -0700, Song Liu wrote:
> On Tue, Jul 1, 2025 at 1:32 AM Christian Brauner <brauner at kernel.org> wrote:
> >
> > 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 at gmail.com> wrote:
> > > >
> > > > On Thu, Jun 26, 2025 at 9:04 PM Song Liu <song at kernel.org> wrote:
> > > >>
> > > >> On Thu, Jun 26, 2025 at 7:14 PM Alexei Starovoitov
> > > >> <alexei.starovoitov at gmail.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?
> 
> Here is a fix to kernel/bpf/helprs.c by Eduard:
> https://lore.kernel.org/bpf/20250627175309.2710973-1-eddyz87@gmail.com/
> 
> This fix addresses build errors with certain config.
> 
> Here is my fix to the selftests:
> https://lore.kernel.org/bpf/20250627191221.765921-1-song@kernel.org/
> 
> I didn't CC linux-fsdevel because all the changes are in the
> selftests, and the error is independent of the new code.

Ah great, thank you for the info. That helped and we don't have to care then.