linux-kernel - [PATCH 3.18 21/24] xen/gntdev: Fix off-by-one error when unmapping with holes

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Message-Id: <20180302084240.180620324@linuxfoundation.org>
Date:   Fri,  2 Mar 2018 09:51:18 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ross Lagerwall <ross.lagerwall@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 3.18 21/24] xen/gntdev: Fix off-by-one error when unmapping with holes

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ross Lagerwall <ross.lagerwall@...rix.com>


[ Upstream commit 951a010233625b77cde3430b4b8785a9a22968d1 ]

If the requested range has a hole, the calculation of the number of
pages to unmap is off by one. Fix it.

Signed-off-by: Ross Lagerwall <ross.lagerwall@...rix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/xen/gntdev.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -348,10 +348,8 @@ static int unmap_grant_pages(struct gran
 		}
 		range = 0;
 		while (range < pages) {
-			if (map->unmap_ops[offset+range].handle == -1) {
-				range--;
+			if (map->unmap_ops[offset+range].handle == -1)
 				break;
-			}
 			range++;
 		}
 		err = __unmap_grant_pages(map, offset, range);