[34-longterm 136/247] xhci: Fix an error in count_sg_trbs_needed()

Paul Gortmaker
2011-06-23T18:06:56Z

From: Paul Zimmerman <Paul.Zimmerman@synopsys.com>

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.
-------------------

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>
---
drivers/usb/host/xhci-ring.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index e4afa99..34ce5d4 100644
--- 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;
}
--
1.7.4.4