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From:   Nick Crews <ncrews@chromium.org>
Date:   Tue, 18 Jun 2019 11:15:03 -0600
Message-ID: <CAHX4x85sETNNS8gdQYQniCM=K35DjMjdHOihJ76pGPrAoB9gyA@mail.gmail.com>
Subject: Re: [PATCH][next] platform/chrome: wilco_ec: fix null pointer
 dereference on failed kzalloc
To:     Colin King <colin.king@canonical.com>
Cc:     Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        kernel-janitors@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>
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Thanks Colin, good catch.

Enric, could you squash this into the real commit?

On Tue, Jun 18, 2019 at 9:39 AM Colin King <colin.king@canonical.com> wrote:
>
> From: Colin Ian King <colin.king@canonical.com>
>
> If the kzalloc of the entries queue q fails a null pointer dereference
> occurs when accessing q->capacity and q->lock.  Add a kzalloc failure
> check and handle the null return case in the calling function
> event_device_add.
>
> Addresses-Coverity: ("Dereference null return")
> Fixes: 75589e37d1dc ("platform/chrome: wilco_ec: Add circular buffer as event queue")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/platform/chrome/wilco_ec/event.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> 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;
>
>         q->capacity = capacity;
>         spin_lock_init(&q->lock);
> @@ -474,6 +477,11 @@ static int event_device_add(struct acpi_device *adev)
>         /* Initialize the device data. */
>         adev->driver_data = dev_data;
>         dev_data->events = event_queue_new(queue_size);
> +       if (!dev_data->events) {
> +               kfree(dev_data);
> +               error = -ENOMEM;
> +               goto free_minor;
> +       }
>         init_waitqueue_head(&dev_data->wq);
>         dev_data->exist = true;
>         atomic_set(&dev_data->available, 1);

Signed-off-by: Nick Crews <ncrews@chromium.org>

> --
> 2.20.1
>