netdev - [PATCH bpf-next 1/8] bpf: Invoke btf_struct_access() callback only for writes.

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Date:   Mon,  3 Apr 2023 21:50:22 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     davem@...emloft.net
Cc:     daniel@...earbox.net, andrii@...nel.org, martin.lau@...nel.org,
        void@...ifault.com, davemarchevsky@...a.com, tj@...nel.org,
        memxor@...il.com, netdev@...r.kernel.org, bpf@...r.kernel.org,
        kernel-team@...com
Subject: [PATCH bpf-next 1/8] bpf: Invoke btf_struct_access() callback only for writes.

From: Alexei Starovoitov <ast@...nel.org>

Remove duplicated if (atype == BPF_READ) btf_struct_access() from
btf_struct_access() callback and invoke it only for writes.

Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
 kernel/bpf/verifier.c          | 2 +-
 net/bpf/bpf_dummy_struct_ops.c | 2 +-
 net/core/filter.c              | 6 ------
 net/ipv4/bpf_tcp_ca.c          | 3 ---
 4 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index eaf9c5291cf0..83984568ccb4 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5504,7 +5504,7 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	if (env->ops->btf_struct_access && !type_is_alloc(reg->type)) {
+	if (env->ops->btf_struct_access && !type_is_alloc(reg->type) && atype == BPF_WRITE) {
 		if (!btf_is_kernel(reg->btf)) {
 			verbose(env, "verifier internal error: reg->btf must be kernel btf\n");
 			return -EFAULT;
diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
index ff4f89a2b02a..9535c8506cda 100644
--- a/net/bpf/bpf_dummy_struct_ops.c
+++ b/net/bpf/bpf_dummy_struct_ops.c
@@ -198,7 +198,7 @@ static int bpf_dummy_ops_btf_struct_access(struct bpf_verifier_log *log,
 	if (err < 0)
 		return err;
 
-	return atype == BPF_READ ? err : NOT_INIT;
+	return NOT_INIT;
 }
 
 static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
diff --git a/net/core/filter.c b/net/core/filter.c
index 3370efad1dda..8b9f409a2ec3 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -8753,9 +8753,6 @@ static int tc_cls_act_btf_struct_access(struct bpf_verifier_log *log,
 {
 	int ret = -EACCES;
 
-	if (atype == BPF_READ)
-		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
-
 	mutex_lock(&nf_conn_btf_access_lock);
 	if (nfct_btf_struct_access)
 		ret = nfct_btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
@@ -8830,9 +8827,6 @@ static int xdp_btf_struct_access(struct bpf_verifier_log *log,
 {
 	int ret = -EACCES;
 
-	if (atype == BPF_READ)
-		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
-
 	mutex_lock(&nf_conn_btf_access_lock);
 	if (nfct_btf_struct_access)
 		ret = nfct_btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index ea21c96c03aa..d6465876bbf6 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -78,9 +78,6 @@ static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
 	const struct btf_type *t;
 	size_t end;
 
-	if (atype == BPF_READ)
-		return btf_struct_access(log, reg, off, size, atype, next_btf_id, flag);
-
 	t = btf_type_by_id(reg->btf, reg->btf_id);
 	if (t != tcp_sock_type) {
 		bpf_log(log, "only read is supported\n");
-- 
2.34.1