USB: EHCI: fix NULL pointer dererence in HCDs that use HCD_LOCAL_MEM

If we use the HCD_LOCAL_MEM flag and dma_declare_coherent_memory() to
enforce the host controller's local memory utilization we also need to
disable native scatter-gather support, otherwise hcd_alloc_coherent() in
map_urb_for_dma() is called with urb->transfer_buffer == NULL, that
triggers a NULL pointer dereference.

We can also consider to add a WARN_ON() and return an error code to
better catch this problem in the future.

At the moment no driver seems to hit this bug, so I should
consider this a low-priority fix.

Signed-off-by: Andrea Righi <arighi@develer.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 0358c05..c5753c7 100644 (file)
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1218,6 +1218,11 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
 {
        unsigned char *vaddr;
 
+       if (*vaddr_handle == NULL) {
+               WARN_ON_ONCE(1);
+               return -EFAULT;
+       }
+
        vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
                                 mem_flags, dma_handle);
        if (!vaddr)

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 2a19336..2e704fa 100644 (file)
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -629,7 +629,8 @@ static int ehci_init(struct usb_hcd *hcd)
        ehci->command = temp;
 
        /* Accept arbitrarily long scatter-gather lists */
-       hcd->self.sg_tablesize = ~0;
+       if (!(hcd->driver->flags & HCD_LOCAL_MEM))
+               hcd->self.sg_tablesize = ~0;
        return 0;
 }