On 11/04/2009 07:48 AM, Larry Finger wrote:
At http://marc.info/?l=linux-wireless&m=125695331205062&w=2, a problem
with DMA buffer processing was corrected for the libertas driver. Because
routine usb_fill_bulk_urb() does not check that DMA is possible when
dma_map_single() is called, this condition was not detected until the buffer
was unmapped. By this time memory corruption had occurred.
The situation is fixed by testing the returned DMA address. If not a legal
address, a WARN_ON(1) is executed to provide traceback and the error is
returned.
Signed-off-by: Larry Finger<Larry.Finger-tQ5ms3gMjBLk1uMJSBkQmQ@xxxxxxxxxxxxxxxx>
---
Index: linux-2.6/drivers/usb/core/hcd.c
===================================================================
--- linux-2.6.orig/drivers/usb/core/hcd.c
+++ linux-2.6/drivers/usb/core/hcd.c
@@ -1281,6 +1281,13 @@ static int map_urb_for_dma(struct usb_hc
urb->setup_packet,
sizeof(struct usb_ctrlrequest),
DMA_TO_DEVICE);
+ ret = dma_mapping_error(hcd->self.controller,
+ urb->setup_dma);
+ /* warn if DMA mapping failed */
+ if (ret) {
+ WARN_ON(1);
+ return ret;
+ }
First of all you forgot to add { } around everything under if statement.
I don't think WARN_ON is needed...
dma_mapping_error under most architectures return 0 or 1 so it would be
better to make some real error value. EAGAIN seems to be proper error,
since documentation says that driver should try again later.
I would write this error handler like this:
if (dma_mapping_error(hcd->self.controller, urb->setup_dma))
ret = -EAGAIN;
else if (hcd->driver->flags& HCD_LOCAL_MEM)
ret = hcd_alloc_coherent(
urb->dev->bus, mem_flags,
@@ -1299,6 +1306,13 @@ static int map_urb_for_dma(struct usb_hc
urb->transfer_buffer,
urb->transfer_buffer_length,
dir);
+ ret = dma_mapping_error(hcd->self.controller,
+ urb->transfer_dma);
+ /* warn if DMA mapping failed */
+ if (ret) {
+ WARN_ON(1);
+ return ret;
+ }
ditto
else if (hcd->driver->flags& HCD_LOCAL_MEM) {
ret = hcd_alloc_coherent(
urb->dev->bus, mem_flags,
--
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