2020-06-14 19:08:21

by Gaurav Singh

Subject: [PATCH] [bpf] xdp_redirect_cpu_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_redirect_cpu_user.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/samples/bpf/xdp_redirect_cpu_user.c b/samples/bpf/xdp_redirect_cpu_user.c
index f3468168982e..2ae7a9a1d950 100644
--- a/samples/bpf/xdp_redirect_cpu_user.c
+++ b/samples/bpf/xdp_redirect_cpu_user.c
@@ -207,11 +207,8 @@ 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);
@@ -222,11 +219,9 @@ static struct datarec *alloc_record_per_cpu(void)
static struct stats_record *alloc_stats_record(void)
{
struct stats_record *rec;
- int i, size;
+ int i;

- size = sizeof(*rec) + n_cpus * sizeof(struct record);
- rec = malloc(size);
- memset(rec, 0, size);
+ rec = calloc(n_cpus + 1, sizeof(struct record));
if (!rec) {
fprintf(stderr, "Mem alloc error\n");
exit(EXIT_FAIL_MEM);
--
2.17.1

2020-06-16 07:09:57

by John Fastabend

Subject: RE: [PATCH] [bpf] xdp_redirect_cpu_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_redirect_cpu_user.c | 11 +++--------
> 1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/samples/bpf/xdp_redirect_cpu_user.c b/samples/bpf/xdp_redirect_cpu_user.c
> index f3468168982e..2ae7a9a1d950 100644
> --- a/samples/bpf/xdp_redirect_cpu_user.c
> +++ b/samples/bpf/xdp_redirect_cpu_user.c
> @@ -207,11 +207,8 @@ 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);
> @@ -222,11 +219,9 @@ static struct datarec *alloc_record_per_cpu(void)
> static struct stats_record *alloc_stats_record(void)
> {
> struct stats_record *rec;
> - int i, size;
> + int i;
>
> - size = sizeof(*rec) + n_cpus * sizeof(struct record);
> - rec = malloc(size);
> - memset(rec, 0, size);
> + rec = calloc(n_cpus + 1, sizeof(struct record));
> if (!rec) {
> fprintf(stderr, "Mem alloc error\n");
> exit(EXIT_FAIL_MEM);
> --
> 2.17.1
>

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

2020-06-16 13:13:00

by Daniel Borkmann

Subject: Re: [PATCH] [bpf] xdp_redirect_cpu_user: Fix null pointer dereference

On 6/14/20 9:04 PM, 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]>

Squashed all three same fixes into one and pushed to bpf, thanks!

> @@ -222,11 +219,9 @@ static struct datarec *alloc_record_per_cpu(void)
> static struct stats_record *alloc_stats_record(void)
> {
> struct stats_record *rec;
> - int i, size;
> + int i;
>
> - size = sizeof(*rec) + n_cpus * sizeof(struct record);
> - rec = malloc(size);
> - memset(rec, 0, size);
> + rec = calloc(n_cpus + 1, sizeof(struct record));

For the record, this one is buggy, so I fixed it up as well.

> if (!rec) {
> fprintf(stderr, "Mem alloc error\n");
> exit(EXIT_FAIL_MEM);
>

Thanks,
Daniel