linux-kernel - [PATCH] libbpf: adjust OPTS_VALID logic, so that it can be used correctly

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Date:   Wed, 14 Sep 2022 20:34:23 +0800
From:   Xin Liu <liuxin350@...wei.com>
To:     <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
        <martin.lau@...ux.dev>, <song@...nel.org>, <yhs@...com>,
        <john.fastabend@...il.com>, <kpsingh@...nel.org>, <sdf@...gle.com>,
        <haoluo@...gle.com>, <jolsa@...nel.org>
CC:     <bpf@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yanan@...wei.com>, <wuchangye@...wei.com>,
        <xiesongyang@...wei.com>, <zhudi2@...wei.com>,
        <kongweibin2@...wei.com>, <liuxin350@...wei.com>
Subject: [PATCH] libbpf: adjust OPTS_VALID logic, so that it can be used correctly

We found that function btf_dump__dump_type_data can be called by the user
as an api, but in this function, the `opts` parameter may be used as a
null pointer, because OPTS_VALID can't properly prevent opts used as null
pointers during verification. Therefore, we fix this problem through this
modification.

This modification has no impact on other places where OPTS_VALID has been
used.

Fixes: 2ce8450ef5a3 ("libbpf: add bpf_object__open_{file, mem} w/ extensible opts")
Signed-off-by: Xin Liu <liuxin350@...wei.com>
---
 tools/lib/bpf/libbpf_internal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 377642ff51fc..29d3267ba56a 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -294,7 +294,7 @@ static inline bool libbpf_validate_opts(const char *opts,
 }
 
 #define OPTS_VALID(opts, type)						      \
-	(!(opts) || libbpf_validate_opts((const char *)opts,		      \
+	((opts) && libbpf_validate_opts((const char *)opts,		      \
 					 offsetofend(struct type,	      \
 						     type##__last_field),     \
 					 (opts)->sz, #type))
-- 
2.33.0