USB: set device dma_mask without reference to global data

Many USB host drivers contain code such as:

if (!pdev->dev.dma_mask)
        pdev->dev.dma_mask = &tegra_ehci_dma_mask;

... where tegra_ehci_dma_mask is a global. I suspect this code originated
in commit 4a53f4e "USB: ehci-tegra: add probing through device tree" and
was simply copied everywhere else.

This works fine when the code is built-in, but can cause a crash when the
code is in a module. The first module load sets up the dma_mask pointer,
but if the module is removed and re-inserted, the value is now non-NULL,
and hence is not updated to point at the new location, and hence points
at a stale location within the previous module load address, which in
turn causes a crash if the pointer is de-referenced.

The simplest way of solving this seems to be to copy the code from
ehci-platform.c, which uses the coherent_dma_mask as the target for the
dma_mask pointer.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/usb/host/ehci-atmel.c b/drivers/usb/host/ehci-atmel.c
index 66420097c242..02f4611faa62 100644
--- a/drivers/usb/host/ehci-atmel.c
+++ b/drivers/usb/host/ehci-atmel.c
@@ -63,8 +63,6 @@ static void atmel_stop_ehci(struct platform_device *pdev)
 
 /*-------------------------------------------------------------------------*/
 
-static u64 at91_ehci_dma_mask = DMA_BIT_MASK(32);
-
 static int ehci_atmel_drv_probe(struct platform_device *pdev)
 {
         struct usb_hcd *hcd;
@@ -93,7 +91,9 @@ static int ehci_atmel_drv_probe(struct platform_device *pdev)
          * Once we have dma capability bindings this can go away.
          */
         if (!pdev->dev.dma_mask)
-                pdev->dev.dma_mask = &at91_ehci_dma_mask;
+                pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
+        if (!pdev->dev.coherent_dma_mask)
+                pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
 
         hcd = usb_create_hcd(driver, &pdev->dev, dev_name(&pdev->dev));
         if (!hcd) {