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

From: Daniel Borkmann <daniel@iogearbox.net>
To: Gaurav Singh <gaurav1086@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	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>,
	"open list:BPF (Safe dynamic programs and tools)" 
	<netdev@vger.kernel.org>,
	"open list:BPF (Safe dynamic programs and tools)" 
	<bpf@vger.kernel.org>, open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] [bpf] xdp_redirect_cpu_user: Fix null pointer dereference
Date: Tue, 16 Jun 2020 15:10:14 +0200	[thread overview]
Message-ID: <f803b1ad-cccd-750f-01e4-e1769ab1d538@iogearbox.net> (raw)
In-Reply-To: <20200614190434.31321-1-gaurav1086@gmail.com>

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 <gaurav1086@gmail.com>

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