2020-06-14 18:43:42

by Gaurav Singh

Subject: [PATCH] [bpf] xdp_monitor_user: Fix null pointer dereference

Memset() on the pointer right after malloc() can cause
a null pointer dereference if it failed to allocate memory.
Fix this by replacing malloc/memset with a single calloc().

Signed-off-by: Gaurav Singh <[email protected]>
---
samples/bpf/xdp_monitor_user.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/samples/bpf/xdp_monitor_user.c b/samples/bpf/xdp_monitor_user.c
index dd558cbb2309..ef53b93db573 100644
--- a/samples/bpf/xdp_monitor_user.c
+++ b/samples/bpf/xdp_monitor_user.c
@@ -509,11 +509,8 @@ static void *alloc_rec_per_cpu(int record_size)
{
unsigned int nr_cpus = bpf_num_possible_cpus();
void *array;
- size_t size;

- size = record_size * nr_cpus;
- array = malloc(size);
- memset(array, 0, size);
+ array = calloc(nr_cpus, record_size);
if (!array) {
fprintf(stderr, "Mem alloc error (nr_cpus:%u)\n", nr_cpus);
exit(EXIT_FAIL_MEM);
@@ -528,8 +525,7 @@ static struct stats_record *alloc_stats_record(void)
int i;

/* Alloc main stats_record structure */
- rec = malloc(sizeof(*rec));
- memset(rec, 0, sizeof(*rec));
+ rec = calloc(1, sizeof(*rec));
if (!rec) {
fprintf(stderr, "Mem alloc error\n");
exit(EXIT_FAIL_MEM);
--
2.17.1

2020-06-16 07:08:19

by John Fastabend

Subject: RE: [PATCH] [bpf] xdp_monitor_user: Fix null pointer dereference

Gaurav Singh wrote:
> Memset() on the pointer right after malloc() can cause
> a null pointer dereference if it failed to allocate memory.
> Fix this by replacing malloc/memset with a single calloc().
>
> Signed-off-by: Gaurav Singh <[email protected]>
> ---
> samples/bpf/xdp_monitor_user.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/samples/bpf/xdp_monitor_user.c b/samples/bpf/xdp_monitor_user.c
> index dd558cbb2309..ef53b93db573 100644
> --- a/samples/bpf/xdp_monitor_user.c
> +++ b/samples/bpf/xdp_monitor_user.c
> @@ -509,11 +509,8 @@ static void *alloc_rec_per_cpu(int record_size)
> {
> unsigned int nr_cpus = bpf_num_possible_cpus();
> void *array;
> - size_t size;
>
> - size = record_size * nr_cpus;
> - array = malloc(size);
> - memset(array, 0, size);
> + array = calloc(nr_cpus, record_size);
> if (!array) {
> fprintf(stderr, "Mem alloc error (nr_cpus:%u)\n", nr_cpus);
> exit(EXIT_FAIL_MEM);
> @@ -528,8 +525,7 @@ static struct stats_record *alloc_stats_record(void)
> int i;
>
> /* Alloc main stats_record structure */
> - rec = malloc(sizeof(*rec));
> - memset(rec, 0, sizeof(*rec));
> + rec = calloc(1, sizeof(*rec));
> if (!rec) {
> fprintf(stderr, "Mem alloc error\n");
> exit(EXIT_FAIL_MEM);
> --
> 2.17.1
>

Acked-by: John Fastabend <[email protected]>