netdev - Re: [PATCH v2 bpf-next 1/9] libbpf: fix detection of corrupted BPF instructions section

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Date:   Wed, 29 May 2019 18:01:55 +0000
From:   Song Liu <songliubraving@...com>
To:     Andrii Nakryiko <andriin@...com>
CC:     "andrii.nakryiko@...il.com" <andrii.nakryiko@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH v2 bpf-next 1/9] libbpf: fix detection of corrupted BPF
 instructions section



> On May 29, 2019, at 10:36 AM, Andrii Nakryiko <andriin@...com> wrote:
> 
> Ensure that size of a section w/ BPF instruction is exactly a multiple
> of BPF instruction size.
> 
> Signed-off-by: Andrii Nakryiko <andriin@...com>

Acked-by: Song Liu <songliubraving@...com>

> ---
> tools/lib/bpf/libbpf.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ca4432f5b067..c6c9d632624a 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -349,8 +349,11 @@ static int
> bpf_program__init(void *data, size_t size, char *section_name, int idx,
> 		  struct bpf_program *prog)
> {
> -	if (size < sizeof(struct bpf_insn)) {
> -		pr_warning("corrupted section '%s'\n", section_name);
> +	const size_t bpf_insn_sz = sizeof(struct bpf_insn);
> +
> +	if (size == 0 || size % bpf_insn_sz) {
> +		pr_warning("corrupted section '%s', size: %zu\n",
> +			   section_name, size);
> 		return -EINVAL;
> 	}
> 
> @@ -376,9 +379,8 @@ bpf_program__init(void *data, size_t size, char *section_name, int idx,
> 			   section_name);
> 		goto errout;
> 	}
> -	prog->insns_cnt = size / sizeof(struct bpf_insn);
> -	memcpy(prog->insns, data,
> -	       prog->insns_cnt * sizeof(struct bpf_insn));
> +	prog->insns_cnt = size / bpf_insn_sz;
> +	memcpy(prog->insns, data, size);
> 	prog->idx = idx;
> 	prog->instances.fds = NULL;
> 	prog->instances.nr = -1;
> -- 
> 2.17.1
>