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/ohci-at91.c b/drivers/usb/host/ohci-at91.c
index a0cb44f0e724..2ee1496dbc1d 100644
--- a/drivers/usb/host/ohci-at91.c
+++ b/drivers/usb/host/ohci-at91.c
@@ -504,8 +504,6 @@ static const struct of_device_id at91_ohci_dt_ids[] = {
 
 MODULE_DEVICE_TABLE(of, at91_ohci_dt_ids);
 
-static u64 at91_ohci_dma_mask = DMA_BIT_MASK(32);
-
 static int ohci_at91_of_init(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
@@ -522,7 +520,9 @@ static int ohci_at91_of_init(struct platform_device *pdev)
 	 * Once we have dma capability bindings this can go away.
 	 */
 	if (!pdev->dev.dma_mask)
-		pdev->dev.dma_mask = &at91_ohci_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);
 
 	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
 	if (!pdata)