[PATCH 5.7 119/265] bpf, xdp, samples: Fix null pointer dereference in *_user code

Sasha Levin
2020-06-29T18:36:17Z

From: Gaurav Singh <gaurav1086@gmail.com>

[ Upstream commit 6903cdae9f9f08d61e49c16cbef11c293e33a615 ]

Memset on the pointer right after malloc can cause a NULL pointer
deference if it failed to allocate memory. A simple fix is to
replace malloc()/memset() pair with a simple call to calloc().

Fixes: 0fca931a6f21 ("samples/bpf: program demonstrating access to xdp_rxq_info")
Signed-off-by: Gaurav Singh <gaurav1086@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
samples/bpf/xdp_monitor_user.c | 8 ++------
samples/bpf/xdp_redirect_cpu_user.c | 7 ++-----
samples/bpf/xdp_rxq_info_user.c | 13 +++----------
3 files changed, 7 insertions(+), 21 deletions(-)

diff --git a/samples/bpf/xdp_monitor_user.c b/samples/bpf/xdp_monitor_user.c
index dd558cbb23094..ef53b93db5732 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);
diff --git a/samples/bpf/xdp_redirect_cpu_user.c b/samples/bpf/xdp_redirect_cpu_user.c
index 9b8f21abeac47..e86fed5cdb92c 100644
--- a/samples/bpf/xdp_redirect_cpu_user.c
+++ b/samples/bpf/xdp_redirect_cpu_user.c
@@ -210,11 +210,8 @@ 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);
@@ -229,11 +226,11 @@ static struct stats_record *alloc_stats_record(void)

size = sizeof(*rec) + n_cpus * sizeof(struct record);
rec = malloc(size);
- memset(rec, 0, size);
if (!rec) {
fprintf(stderr, "Mem alloc error\n");
exit(EXIT_FAIL_MEM);
}
+ memset(rec, 0, size);
rec->rx_cnt.cpu = alloc_record_per_cpu();
rec->redir_err.cpu = alloc_record_per_cpu();
rec->kthread.cpu = alloc_record_per_cpu();
diff --git a/samples/bpf/xdp_rxq_info_user.c b/samples/bpf/xdp_rxq_info_user.c
index 4fe47502ebed4..caa4e7ffcfc7b 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);
--
2.25.1