Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Yafang Shao <laoar.shao@gmail.com>
To:     ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
        kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
        john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
        haoluo@google.com, jolsa@kernel.org, rostedt@goodmis.org,
        mhiramat@kernel.org
Cc:     bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
        linux-kernel@vger.kernel.org, Yafang Shao <laoar.shao@gmail.com>
Subject: [PATCH bpf-next 1/6] bpf: Add __rcu_read_{lock,unlock} into btf id deny list
Date:   Mon, 17 Apr 2023 15:47:32 +0000
Message-Id: <20230417154737.12740-2-laoar.shao@gmail.com>
In-Reply-To: <20230417154737.12740-1-laoar.shao@gmail.com>
References: <20230417154737.12740-1-laoar.shao@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The tracing recursion prevention mechanism must be protected by rcu, that
leaves __rcu_read_{lock,unlock} unprotected by this mechanism. If we trace
them, the recursion will happen. Let's add them into the btf id deny list.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 kernel/bpf/verifier.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5dae11e..83fb94f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18645,6 +18645,10 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 BTF_ID(func, preempt_count_add)
 BTF_ID(func, preempt_count_sub)
 #endif
+#ifdef CONFIG_PREEMPT_RCU
+BTF_ID(func, __rcu_read_lock)
+BTF_ID(func, __rcu_read_unlock)
+#endif
 BTF_SET_END(btf_id_deny)
 
 static bool can_be_sleepable(struct bpf_prog *prog)
-- 
1.8.3.1