linux-kernel - [PATCH bpf-next] bpf: Add rcu ptr in btf_id_sock_common

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Message-Id: <20241008080916.44724-1-lulie@linux.alibaba.com>
Date: Tue,  8 Oct 2024 16:09:16 +0800
From: Philo Lu <lulie@...ux.alibaba.com>
To: bpf@...r.kernel.org
Cc: ast@...nel.org,
	daniel@...earbox.net,
	john.fastabend@...il.com,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
	yonghong.song@...ux.dev,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org,
	xuanzhuo@...ux.alibaba.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next] bpf: Add rcu ptr in btf_id_sock_common_types

Sometimes sk is dereferenced as an rcu ptr, such as skb->sk in tp_btf,
which is a valid type of sock common. Then helpers like bpf_skc_to_*()
can be used with skb->sk.

For example, the following prog will be rejected without this patch:
```
SEC("tp_btf/tcp_bad_csum")
int BPF_PROG(tcp_bad_csum, struct sk_buff* skb)
{
	struct sock *sk = skb->sk;
	struct tcp_sock *tp;

	if (!sk)
		return 0;
	tp = bpf_skc_to_tcp_sock(sk);

	return 0;
}
```

Signed-off-by: Philo Lu <lulie@...ux.alibaba.com>
---
 kernel/bpf/verifier.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9a7ed527e47e..3e7ce448ae03 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8362,6 +8362,7 @@ static const struct bpf_reg_types btf_id_sock_common_types = {
 		PTR_TO_XDP_SOCK,
 		PTR_TO_BTF_ID,
 		PTR_TO_BTF_ID | PTR_TRUSTED,
+		PTR_TO_BTF_ID | MEM_RCU,
 	},
 	.btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
 };
-- 
2.32.0.3.g01195cf9f