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

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Message-ID: <nw73mlf4p4qpjeoc6jie76xxmvl2iuj2f6p44sq2p5x2dzdrcv@iekulfikhdc4>
Date: Thu, 20 Feb 2025 10:00:00 -0500
From: Ethan Carter Edwards <ethan@...ancedwards.com>
To: Pu Lehui <pulehui@...wei.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, 
	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 25/02/20 08:24PM, Pu Lehui wrote:
> 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.

You are right. My apologies. I should probably do less coding at 2AM.

Thanks,
Ethan