Re: [PATCH v4] staging: gdm724x: Fix DMA from stack

[gre...@linuxfoundation.org]

On Thu, Feb 11, 2021 at 01:28:41PM +, David Laight wrote:
> > Stack allocated buffers cannot be used for DMA
> > on all architectures so allocate hci_packet buffer
> > using kmalloc.
> 
> I wonder if the usb stack ought/could support a short bounce
> buffer within the memory is already has to allocate?

No.

RE: [PATCH v4] staging: gdm724x: Fix DMA from stack

[David Laight]

> Stack allocated buffers cannot be used for DMA
> on all architectures so allocate hci_packet buffer
> using kmalloc.

I wonder if the usb stack ought/could support a short bounce
buffer within the memory is already has to allocate?

For hci and lengths less than 8 the immediate data can be
placed directly in the ring structure replacing the data
pointer itself.

David

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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, 
UK
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Re: [PATCH v4] staging: gdm724x: Fix DMA from stack

[Dan Carpenter]

On Thu, Feb 11, 2021 at 11:08:19AM +0530, Amey Narkhede wrote:
> Stack allocated buffers cannot be used for DMA
> on all architectures so allocate hci_packet buffer
> using kmalloc.
> 
> Signed-off-by: Amey Narkhede 

Looks good.

Reviewed-by: Dan Carpenter 

regards,
dan carpenter

[PATCH v4] staging: gdm724x: Fix DMA from stack

[Amey Narkhede]

Stack allocated buffers cannot be used for DMA
on all architectures so allocate hci_packet buffer
using kmalloc.

Signed-off-by: Amey Narkhede 
---
Changes in v4:
- Use struct_size to allocate memory for hci_packet
- Fix memory corruption

 drivers/staging/gdm724x/gdm_usb.c | 10 +++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/gdm724x/gdm_usb.c 
b/drivers/staging/gdm724x/gdm_usb.c
index dc4da66c3..54bdb64f5 100644
--- a/drivers/staging/gdm724x/gdm_usb.c
+++ b/drivers/staging/gdm724x/gdm_usb.c
@@ -56,20 +56,24 @@ static int gdm_usb_recv(void *priv_dev,

 static int request_mac_address(struct lte_udev *udev)
 {
-   u8 buf[16] = {0,};
-   struct hci_packet *hci = (struct hci_packet *)buf;
+   struct hci_packet *hci;
struct usb_device *usbdev = udev->usbdev;
int actual;
int ret = -1;

+   hci = kmalloc(struct_size(hci, data, 1), GFP_KERNEL);
+   if (!hci)
+   return -ENOMEM;
+
hci->cmd_evt = gdm_cpu_to_dev16(udev->gdm_ed, LTE_GET_INFORMATION);
hci->len = gdm_cpu_to_dev16(udev->gdm_ed, 1);
hci->data[0] = MAC_ADDRESS;

-   ret = usb_bulk_msg(usbdev, usb_sndbulkpipe(usbdev, 2), buf, 5,
+   ret = usb_bulk_msg(usbdev, usb_sndbulkpipe(usbdev, 2), hci, 5,
   , 1000);

udev->request_mac_addr = 1;
+   kfree(hci);

return ret;
 }
--
2.30.1