xhci: Fix an error in count_sg_trbs_needed()

commit bcd2fde05341cef0052e49566ec88b406a521cf3 upstream.

The expression

	while (running_total < sg_dma_len(sg))

does not take into account that the remaining data length can be less
than sg_dma_len(sg). In that case, running_total can end up being
greater than the total data length, so an extra TRB is counted.
Changing the expression to

	while (running_total < sg_dma_len(sg) && running_total < temp)

fixes that.

This patch should be queued for stable kernels back to 2.6.31.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index e4afa994257f5008f6117e43c2c44395e177eb89..34ce5d4931040802a99d590f8cb35016d44f1b66 100644 (file)
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1716,7 +1716,7 @@ static unsigned int count_sg_trbs_needed(struct xhci_hcd *xhci, struct urb *urb)
                        num_trbs++;
 
                /* How many more 64KB chunks to transfer, how many more TRBs? */
-               while (running_total < sg_dma_len(sg)) {
+               while (running_total < sg_dma_len(sg) && running_total < temp) {
                        num_trbs++;
                        running_total += TRB_MAX_BUFF_SIZE;
                }