netdev - Re: [PATCH] xdp_rxq_info_user: Replace malloc/memset w/calloc

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Date:   Thu, 11 Jun 2020 20:01:40 +0200
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Gaurav Singh <gaurav1086@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        KP Singh <kpsingh@...omium.org>,
        netdev@...r.kernel.org (open list:XDP (eXpress Data Path)),
        bpf@...r.kernel.org (open list:XDP (eXpress Data Path)),
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH] xdp_rxq_info_user: Replace malloc/memset w/calloc

On Thu, 11 Jun 2020 11:02:21 -0400
Gaurav Singh <gaurav1086@...il.com> wrote:

> Replace malloc/memset with calloc

Please also mention/describe  that this also solves the bug you found.

As this fix a potential bug, it will be appropriate to add a "Fixes:"
line, just before "Signed-off-by" (meaning no newline between the two).

Fixes: 0fca931a6f21 ("samples/bpf: program demonstrating access to xdp_rxq_info")
> Signed-off-by: Gaurav Singh <gaurav1086@...il.com>
> ---
>  samples/bpf/xdp_rxq_info_user.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
> 
> diff --git a/samples/bpf/xdp_rxq_info_user.c b/samples/bpf/xdp_rxq_info_user.c
> index 4fe47502ebed..caa4e7ffcfc7 100644
> --- a/samples/bpf/xdp_rxq_info_user.c
> +++ b/samples/bpf/xdp_rxq_info_user.c
> @@ -198,11 +198,8 @@ static struct datarec *alloc_record_per_cpu(void)
>  {
>  	unsigned int nr_cpus = bpf_num_possible_cpus();
>  	struct datarec *array;
> -	size_t size;
>  
> -	size = sizeof(struct datarec) * nr_cpus;
> -	array = malloc(size);
> -	memset(array, 0, size);
> +	array = calloc(nr_cpus, sizeof(struct datarec));
>  	if (!array) {
>  		fprintf(stderr, "Mem alloc error (nr_cpus:%u)\n", nr_cpus);
>  		exit(EXIT_FAIL_MEM);
> @@ -214,11 +211,8 @@ static struct record *alloc_record_per_rxq(void)
>  {
>  	unsigned int nr_rxqs = bpf_map__def(rx_queue_index_map)->max_entries;
>  	struct record *array;
> -	size_t size;
>  
> -	size = sizeof(struct record) * nr_rxqs;
> -	array = malloc(size);
> -	memset(array, 0, size);
> +	array = calloc(nr_rxqs, sizeof(struct record));
>  	if (!array) {
>  		fprintf(stderr, "Mem alloc error (nr_rxqs:%u)\n", nr_rxqs);
>  		exit(EXIT_FAIL_MEM);
> @@ -232,8 +226,7 @@ static struct stats_record *alloc_stats_record(void)
>  	struct stats_record *rec;
>  	int i;
>  
> -	rec = malloc(sizeof(*rec));
> -	memset(rec, 0, sizeof(*rec));
> +	rec = calloc(1, sizeof(struct stats_record));
>  	if (!rec) {
>  		fprintf(stderr, "Mem alloc error\n");
>  		exit(EXIT_FAIL_MEM);



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