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From:   Gaurav Singh <gaurav1086@gmail.com>
To:     gaurav1086@gmail.com, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        netdev@vger.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        bpf@vger.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH] [bpf] xdp_monitor_user: Fix null pointer dereference
Date:   Sun, 14 Jun 2020 14:41:02 -0400
Message-Id: <20200614184102.30992-1-gaurav1086@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@gmail.com>
---
 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