linux-kernel - [34-longterm 136/247] xhci: Fix an error in count_sg_trbs

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Message-Id: <1308850515-15242-77-git-send-email-paul.gortmaker@windriver.com>
Date:	Thu, 23 Jun 2011 13:33:24 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org,
	Paul Zimmerman <Paul.Zimmerman@...opsys.com>,
	Paul Zimmerman <paulz@...opsys.com>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 136/247] xhci: Fix an error in count_sg_trbs_needed()

From: Paul Zimmerman <Paul.Zimmerman@...opsys.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@...opsys.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@...ux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.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

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