linux-kernel - [PATCH bpf-next v1 0/2] bpf: Fix panic in bpf_get_local

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Message-ID: <20250417044041.252874-1-jiayuan.chen@linux.dev>
Date: Thu, 17 Apr 2025 12:40:13 +0800
From: Jiayuan Chen <jiayuan.chen@...ux.dev>
To: andrii@...nel.org,
	martin.lau@...ux.dev,
	bpf@...r.kernel.org
Cc: alexis.lothore@...tlin.com,
	mrpre@....com,
	Jiayuan Chen <jiayuan.chen@...ux.dev>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Mykola Lysenko <mykolal@...com>,
	Shuah Khan <shuah@...nel.org>,
	Alan Maguire <alan.maguire@...cle.com>,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: [PATCH bpf-next v1 0/2] bpf: Fix panic in bpf_get_local_storage

The selftest I provided can reproduce a panic:
'./test_progs -a cgroup_storage_update'

When we attach a program to cgroup and if prog->aux->cgroup_storage
exists, which means the cgroup_storage map is used in the program, we
will then allocate storage by bpf_cgroup_storages_alloc() and assign it
to pl->storage.

At the end, pl->storage will be assigned to
cgrp->bpf.effective[atype]->cgroup_storage by xxx_effective_progs().

But when we attach a program without the cgroup_storage map being used
(prog->aux->cgroup_storage is empty), the cgroup_storage in struct
bpf_prog_array_item is empty.

Then, if we use BPF_LINK_UPDATE to replace the old program with a new one
that uses the cgroup_storage map, we miss the cgroup_storage being
initialized.

This causes a panic when accessing storage in bpf_get_local_storage.

Jiayuan Chen (2):
  bpf: Create cgroup storage if needed when updating link
  selftests/bpf: Add link update test for cgroup_storage

 kernel/bpf/cgroup.c                           | 24 +++++++---
 .../selftests/bpf/prog_tests/cgroup_storage.c | 45 +++++++++++++++++++
 .../selftests/bpf/progs/cgroup_storage.c      |  6 +++
 3 files changed, 70 insertions(+), 5 deletions(-)

-- 
2.47.1