linux-kernel - [PATCH] btf: move kern_type_id to goto cand_cache

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Message-Id: <20250220-bpf-uninit-v1-1-af07a5a57e5b@ethancedwards.com>
Date: Thu, 20 Feb 2025 00:50:53 -0500
From: Ethan Carter Edwards <ethan@...ancedwards.com>
To: Andrii Nakryiko <andrii@...nel.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>, 
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>, bpf@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
 Ethan Carter Edwards <ethan@...ancedwards.com>
Subject: [PATCH] btf: move kern_type_id to goto cand_cache_unlock

In most code paths variable move_kern_type_id remains uninitialized upon
return. By moving it to the goto, it is initialized in these code paths.
As well as others. Caught by Coverity.

Closes: https://scan5.scan.coverity.com/#/project-view/63874/10063?selectedIssue=1595567
Fixes: e2b3c4ff5d183d ("bpf: add __arg_trusted global func arg tag")
Signed-off-by: Ethan Carter Edwards <ethan@...ancedwards.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 9de6acddd479b4f5e32a5e6ba43cf369de4cee29..8c82ced7da299ad1ad769024fe097898c269013b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7496,9 +7496,9 @@ static int btf_get_ptr_to_btf_id(struct bpf_verifier_log *log, int arg_idx,
 		err = -EOPNOTSUPP;
 		goto cand_cache_unlock;
 	}
-	kern_type_id = cc->cands[0].id;
 
 cand_cache_unlock:
+	kern_type_id = cc->cands[0].id;
 	mutex_unlock(&cand_cache_mutex);
 	if (err)
 		return err;

---
base-commit: 87a132e73910e8689902aed7f2fc229d6908383b
change-id: 20250220-bpf-uninit-3323a4426da9

Best regards,
-- 
Ethan Carter Edwards <ethan@...ancedwards.com>