linux-kernel - [PATCH bpf-next] bpf: Fix maximum permitted number of arguments check

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Date:   Fri, 25 Mar 2022 00:42:38 +0800
From:   Yuntao Wang <ytcoode@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yuntao Wang <ytcoode@...il.com>
Subject: [PATCH bpf-next] bpf: Fix maximum permitted number of arguments check

Since the m->arg_size array can hold up to MAX_BPF_FUNC_ARGS argument
sizes, it's ok that nargs is equal to MAX_BPF_FUNC_ARGS.

Signed-off-by: Yuntao Wang <ytcoode@...il.com>
---
 kernel/bpf/btf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 24788ce564a0..0918a39279f6 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5507,7 +5507,7 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
 	}
 	args = (const struct btf_param *)(func + 1);
 	nargs = btf_type_vlen(func);
-	if (nargs >= MAX_BPF_FUNC_ARGS) {
+	if (nargs > MAX_BPF_FUNC_ARGS) {
 		bpf_log(log,
 			"The function %s has %d arguments. Too many.\n",
 			tname, nargs);
-- 
2.35.1