usb; xhci: Fix TRB offset calculations.

Greg KH introduced a bug into xhci_trb_virt_to_dma() when he changed the
type of offset to dma_addr_t from unsigned int and dropped the casts to
unsigned int around the virtual address pointer subtraction.

trb and seg->trbs are both valid pointers to virtual addresses, so the
compiler will mod the subtraction by the size of union trb (16 bytes).
segment_offset is an unsigned long, which is guaranteed to be at least as
big as a void *.

Drop the void * casts in the first if statement because trb and seg->trbs
are both pointers of the same type (pointers to union trb).

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index d42a738..02d8198 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -74,16 +74,15 @@
 dma_addr_t xhci_trb_virt_to_dma(struct xhci_segment *seg,
                union xhci_trb *trb)
 {
-       dma_addr_t offset;
+       unsigned long segment_offset;
 
-       if (!seg || !trb || (void *) trb < (void *) seg->trbs)
+       if (!seg || !trb || trb < seg->trbs)
                return 0;
-       /* offset in bytes, since these are byte-addressable */
-       offset = trb - seg->trbs;
-       /* SEGMENT_SIZE in bytes, trbs are 16-byte aligned */
-       if (offset > SEGMENT_SIZE || (offset % sizeof(*trb)) != 0)
+       /* offset in TRBs */
+       segment_offset = trb - seg->trbs;
+       if (segment_offset > TRBS_PER_SEGMENT)
                return 0;
-       return seg->dma + offset;
+       return seg->dma + (segment_offset * sizeof(*trb));
 }
 
 /* Does this link TRB point to the first segment in a ring,