[PATCH] xdp_rxq_info_user: Add null check after malloc

[PATCH] xdp_rxq_info_user: Add null check after malloc

[Gaurav Singh]

Signed-off-by: Gaurav Singh <gaurav1086@gmail.com>

The memset call is made right after malloc call which
can return a NULL pointer upon failure causing a 
segmentation fault. Fix this by adding a null check 
right after malloc() and then do memset().

---
 samples/bpf/xdp_rxq_info_user.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/samples/bpf/xdp_rxq_info_user.c b/samples/bpf/xdp_rxq_info_user.c
index 4fe47502ebed..2d03c84a4cca 100644
--- a/samples/bpf/xdp_rxq_info_user.c
+++ b/samples/bpf/xdp_rxq_info_user.c
@@ -202,11 +202,11 @@ static struct datarec *alloc_record_per_cpu(void)
 
 	size = sizeof(struct datarec) * nr_cpus;
 	array = malloc(size);
-	memset(array, 0, size);
 	if (!array) {
 		fprintf(stderr, "Mem alloc error (nr_cpus:%u)\n", nr_cpus);
 		exit(EXIT_FAIL_MEM);
 	}
+	memset(array, 0, size);
 	return array;
 }
 
@@ -218,11 +218,11 @@ static struct record *alloc_record_per_rxq(void)
 
 	size = sizeof(struct record) * nr_rxqs;
 	array = malloc(size);
-	memset(array, 0, size);
 	if (!array) {
 		fprintf(stderr, "Mem alloc error (nr_rxqs:%u)\n", nr_rxqs);
 		exit(EXIT_FAIL_MEM);
 	}
+	memset(array, 0, size);
 	return array;
 }
 
@@ -233,11 +233,11 @@ static struct stats_record *alloc_stats_record(void)
 	int i;
 
 	rec = malloc(sizeof(*rec));
-	memset(rec, 0, sizeof(*rec));
 	if (!rec) {
 		fprintf(stderr, "Mem alloc error\n");
 		exit(EXIT_FAIL_MEM);
 	}
+	memset(rec, 0, sizeof(*rec));
 	rec->rxq = alloc_record_per_rxq();
 	for (i = 0; i < nr_rxqs; i++)
 		rec->rxq[i].cpu = alloc_record_per_cpu();
-- 
2.17.1

Re: [PATCH] xdp_rxq_info_user: Add null check after malloc

[Daniel Borkmann]

On 6/10/20 5:01 AM, Gaurav Singh wrote:
> Signed-off-by: Gaurav Singh <gaurav1086@gmail.com>
> 
> The memset call is made right after malloc call which
> can return a NULL pointer upon failure causing a
> segmentation fault. Fix this by adding a null check
> right after malloc() and then do memset().

The SoB should come after the commit message here.

> ---
>   samples/bpf/xdp_rxq_info_user.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/samples/bpf/xdp_rxq_info_user.c b/samples/bpf/xdp_rxq_info_user.c
> index 4fe47502ebed..2d03c84a4cca 100644
> --- a/samples/bpf/xdp_rxq_info_user.c
> +++ b/samples/bpf/xdp_rxq_info_user.c
> @@ -202,11 +202,11 @@ static struct datarec *alloc_record_per_cpu(void)
>   
>   	size = sizeof(struct datarec) * nr_cpus;
>   	array = malloc(size);
> -	memset(array, 0, size);

All these below are candidates for calloc(), can we just use that instead and
simplify the below.

>   	if (!array) {
>   		fprintf(stderr, "Mem alloc error (nr_cpus:%u)\n", nr_cpus);
>   		exit(EXIT_FAIL_MEM);
>   	}
> +	memset(array, 0, size);
>   	return array;
>   }
>   
> @@ -218,11 +218,11 @@ static struct record *alloc_record_per_rxq(void)
>   
>   	size = sizeof(struct record) * nr_rxqs;
>   	array = malloc(size);
> -	memset(array, 0, size);
>   	if (!array) {
>   		fprintf(stderr, "Mem alloc error (nr_rxqs:%u)\n", nr_rxqs);
>   		exit(EXIT_FAIL_MEM);
>   	}
> +	memset(array, 0, size);
>   	return array;
>   }
>   
> @@ -233,11 +233,11 @@ static struct stats_record *alloc_stats_record(void)
>   	int i;
>   
>   	rec = malloc(sizeof(*rec));
> -	memset(rec, 0, sizeof(*rec));
>   	if (!rec) {
>   		fprintf(stderr, "Mem alloc error\n");
>   		exit(EXIT_FAIL_MEM);
>   	}
> +	memset(rec, 0, sizeof(*rec));
>   	rec->rxq = alloc_record_per_rxq();
>   	for (i = 0; i < nr_rxqs; i++)
>   		rec->rxq[i].cpu = alloc_record_per_cpu();
> 

Thanks,
Daniel