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

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Message-ID: <CAADnVQ+pPt7Zt8gS0aW75WGrwjmcUcn3s37Ahd9bnLyzOfB=3g@mail.gmail.com>
Date: Tue, 1 Jul 2025 07:51:55 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Christian Brauner <brauner@...nel.org>
Cc: 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 Tue, Jul 1, 2025 at 1:32 AM Christian Brauner <brauner@...nel.org> wrote:
>
> On Thu, Jun 26, 2025 at 07:14:20PM -0700, Alexei Starovoitov wrote:
> > On Mon, Jun 23, 2025 at 4:03 AM Christian Brauner <brauner@...nel.org> wrote:
> > >
> > > On Sun, 22 Jun 2025 23:38:50 -0700, Song Liu wrote:
> > > > Introduce a new kfunc bpf_cgroup_read_xattr, which can read xattr from
> > > > cgroupfs nodes. The primary users are LSMs, cgroup programs, and sched_ext.
> > > >
> > >
> > > Applied to the vfs-6.17.bpf branch of the vfs/vfs.git tree.
> > > Patches in the vfs-6.17.bpf branch should appear in linux-next soon.
> >
> > Thanks.
> > Now merged into bpf-next/master as well.
> >
> > > Please report any outstanding bugs that were missed during review in a
> > > new review to the original patch series allowing us to drop it.
> >
> > bugs :(
> >
> > > It's encouraged to provide Acked-bys and Reviewed-bys even though the
> > > patch has now been applied. If possible patch trailers will be updated.
> >
> > Pls don't. Keep it as-is, otherwise there will be merge conflicts
> > during the merge window.
>
> This is just the common blurb. As soon as another part of the tree
> relies on something we stabilize the branch and only do fixes on top and
> never rebase. We usually recommend just pulling the branch which I think
> you did.
>
> >
> > > Note that commit hashes shown below are subject to change due to rebase,
> > > trailer updates or similar. If in doubt, please check the listed branch.
> > >
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
> > > branch: vfs-6.17.bpf
> > >
> > > [1/4] kernfs: remove iattr_mutex
> > >       https://git.kernel.org/vfs/vfs/c/d1f4e9026007
> > > [2/4] bpf: Introduce bpf_cgroup_read_xattr to read xattr of cgroup's node
> > >       https://git.kernel.org/vfs/vfs/c/535b070f4a80
> > > [3/4] bpf: Mark cgroup_subsys_state->cgroup RCU safe
> > >       https://git.kernel.org/vfs/vfs/c/1504d8c7c702
> > > [4/4] selftests/bpf: Add tests for bpf_cgroup_read_xattr
> > >       https://git.kernel.org/vfs/vfs/c/f4fba2d6d282
> >
> > Something wrong with this selftest.
> > Cleanup is not done correctly.
> >
> > ./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.
>
> We should put that commit on the shared vfs-6.17.bpf branch.

The branch had a conflict with bpf-next which was resolved
in the merge commit. Then _two_ fixes were applied on top.
And one fix is right where conflict was.
So it's not possible to apply both fixes to vfs-6.17.bpf.
imo this shared branch experience wasn't good.
We should have applied the series to bpf-next only.
It was more bpf material than vfs. I wouldn't do this again.