netdev - Re: [PATCH bpf] bpf: btf: Fix end boundary calculation for type section

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Date:   Wed, 12 Sep 2018 10:38:46 -0700
From:   Yonghong Song <yhs@...com>
To:     Martin KaFai Lau <kafai@...com>, <netdev@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>
Subject: Re: [PATCH bpf] bpf: btf: Fix end boundary calculation for type
 section



On 9/12/18 10:29 AM, Martin KaFai Lau wrote:
> The end boundary math for type section is incorrect in
> btf_check_all_metas().  It just happens that hdr->type_off
> is always 0 for now because there are only two sections
> (type and string) and string section must be at the end (ensured
> in btf_parse_str_sec).
> 
> However, type_off may not be 0 if a new section would be added later.
> This patch fixes it.
> 
> Fixes: f80442a4cd18 ("bpf: btf: Change how section is supported in btf_header")
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Martin KaFai Lau <kafai@...com>

Acked-by: Yonghong Song <yhs@...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 2590700237c1..138f0302692e 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -1844,7 +1844,7 @@ static int btf_check_all_metas(struct btf_verifier_env *env)
>   
>   	hdr = &btf->hdr;
>   	cur = btf->nohdr_data + hdr->type_off;
> -	end = btf->nohdr_data + hdr->type_len;
> +	end = cur + hdr->type_len;
>   
>   	env->log_type_id = 1;
>   	while (cur < end) {
>