netdev - [PATCH] [bpf] xdp_redirect_cpu_user: Fix null pointer dereference

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Message-Id: <20200614190434.31321-1-gaurav1086@gmail.com>
Date:   Sun, 14 Jun 2020 15:04:33 -0400
From:   Gaurav Singh <gaurav1086@...il.com>
To:     gaurav1086@...il.com, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        netdev@...r.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        bpf@...r.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        linux-kernel@...r.kernel.org (open list)
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 <gaurav1086@...il.com>
---
 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