linux-kernel - Re: [PATCH][next] platform/chrome: wilco_ec: fix null pointer dereference on failed kzalloc

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Date:   Wed, 19 Jun 2019 08:30:12 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Nick Crews <ncrews@...omium.org>,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] platform/chrome: wilco_ec: fix null pointer
 dereference on failed kzalloc

On Tue, Jun 18, 2019 at 04:39:24PM +0100, Colin King wrote:
> diff --git a/drivers/platform/chrome/wilco_ec/event.c b/drivers/platform/chrome/wilco_ec/event.c
> index c975b76e6255..e251a989b152 100644
> --- a/drivers/platform/chrome/wilco_ec/event.c
> +++ b/drivers/platform/chrome/wilco_ec/event.c
> @@ -112,8 +112,11 @@ module_param(queue_size, int, 0644);
>  static struct ec_event_queue *event_queue_new(int capacity)
>  {
>  	size_t entries_size = sizeof(struct ec_event *) * capacity;
> -	struct ec_event_queue *q = kzalloc(sizeof(*q) + entries_size,
> -					   GFP_KERNEL);
> +	struct ec_event_queue *q;
> +
> +	q = kzalloc(sizeof(*q) + entries_size, GFP_KERNEL);
> +	if (!q)
> +		return NULL;

We have a new struct_size() macro designed for these allocations.

	q = kzalloc(struct_size(q, entries, capacity), GFP_KERNEL);

The advantage is that it checks for integer overflows.

regards,
dan carpenter