netdev - Re: [PATCH net-next v2 1/2] libbpf: parse maps sections of varying size

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Date:   Tue, 3 Oct 2017 16:11:51 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Craig Gallek <kraigatgoog@...il.com>
Cc:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S . Miller" <davem@...emloft.net>,
        Chonggang Li <chonggangli@...gle.com>, netdev@...r.kernel.org,
        brouer@...hat.com, Eric Leblond <eric.leblond@...il.com>
Subject: Re: [PATCH net-next v2 1/2] libbpf: parse maps sections of varying
 size

On Mon,  2 Oct 2017 12:41:28 -0400
Craig Gallek <kraigatgoog@...il.com> wrote:

> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 4f402dcdf372..28b300868ad7 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -580,7 +580,7 @@ bpf_object__init_kversion(struct bpf_object *obj,
>  }
>  
>  static int
> -bpf_object__validate_maps(struct bpf_object *obj)
> +bpf_object__validate_maps(struct bpf_object *obj, int map_def_sz)
>  {
>  	int i;
>  
> @@ -595,9 +595,11 @@ bpf_object__validate_maps(struct bpf_object *obj)
>  		const struct bpf_map *a = &obj->maps[i - 1];
>  		const struct bpf_map *b = &obj->maps[i];
>  
> -		if (b->offset - a->offset < sizeof(struct bpf_map_def)) {
> -			pr_warning("corrupted map section in %s: map \"%s\" too small\n",
> -				   obj->path, a->name);
> +		if (b->offset - a->offset < map_def_sz) {
> +			pr_warning("corrupted map section in %s: map \"%s\" too small "
> +				   "(%zd vs %d)\n",
> +				   obj->path, a->name, b->offset - a->offset,
> +				   map_def_sz);
>  			return -EINVAL;

Hmm... one more comment.  You have just coded handling of ELF
map_def_sz which are smaller in a safe manor, but here this case will
get rejected (in bpf_object__validate_maps).  That cannot be the right
intend?

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer