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

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Message-ID: <c6a25b61-6545-4a03-b2f1-a38c07037d29@huawei.com>
Date: Thu, 20 Feb 2025 20:24:49 +0800
From: Pu Lehui <pulehui@...wei.com>
To: Ethan Carter Edwards <ethan@...ancedwards.com>, 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>
Subject: Re: [PATCH] btf: move kern_type_id to goto cand_cache_unlock

On 2025/2/20 13:50, Ethan Carter Edwards wrote:
> 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;

Hi, for goto's branches, it will always `return err`, no need to make 
this move.

>   	mutex_unlock(&cand_cache_mutex);
>   	if (err)
>   		return err;
> 
> ---
> base-commit: 87a132e73910e8689902aed7f2fc229d6908383b
> change-id: 20250220-bpf-uninit-3323a4426da9
> 
> Best regards,