linux-kernel - Re: [PATCH] staging: gdm724x: Fix DMA from stack

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Message-ID: <YCLJHNvKhiMJmTP8@kroah.com>
Date:   Tue, 9 Feb 2021 18:40:44 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     ameynarkhede03@...il.com
Cc:     devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: gdm724x: Fix DMA from stack

On Tue, Feb 09, 2021 at 08:24:15PM +0530, ameynarkhede03@...il.com wrote:
> From: Amey Narkhede <ameynarkhede03@...il.com>
> 
> Stack allocated buffers cannot be used for DMA
> on all architectures so allocate usbdev buffer
> using kmalloc().
> 
> Signed-off-by: Amey Narkhede <ameynarkhede03@...il.com>
> ---
>  drivers/staging/gdm724x/gdm_usb.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/gdm724x/gdm_usb.c b/drivers/staging/gdm724x/gdm_usb.c
> index dc4da66c3..50dc463d4 100644
> --- a/drivers/staging/gdm724x/gdm_usb.c
> +++ b/drivers/staging/gdm724x/gdm_usb.c
> @@ -56,7 +56,7 @@ static int gdm_usb_recv(void *priv_dev,
> 
>  static int request_mac_address(struct lte_udev *udev)
>  {
> -	u8 buf[16] = {0,};
> +	u8 *buf;
>  	struct hci_packet *hci = (struct hci_packet *)buf;
>  	struct usb_device *usbdev = udev->usbdev;
>  	int actual;
> @@ -66,6 +66,10 @@ static int request_mac_address(struct lte_udev *udev)
>  	hci->len = gdm_cpu_to_dev16(udev->gdm_ed, 1);
>  	hci->data[0] = MAC_ADDRESS;
> 
> +	buf = kmalloc(16, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +

This is great, but you just added a build warning, which implies that
the patch is incorrect.

You also have a memory leak here, which is not acceptable :(

thanks,

greg k-h