linux-kernel - [PATCH 2/2] Drivers: hv: hv_balloon: correctly handle num_pages>INT

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Date:	Tue, 31 Mar 2015 11:16:41 -0700
From:	"K. Y. Srinivasan" <kys@...rosoft.com>
To:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
	vkuznets@...hat.com, jasowang@...hat.com
Cc:	"K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 2/2] Drivers: hv: hv_balloon: correctly handle num_pages>INT_MAX case

From: Vitaly Kuznetsov <vkuznets@...hat.com>

balloon_wrk.num_pages is __u32 and it comes from host in struct dm_balloon
where it is also __u32. We, however, use 'int' in balloon_up() and in case
we happen to receive num_pages>INT_MAX request we'll end up allocating zero
pages as 'num_pages < alloc_unit' check in alloc_balloon_pages() will pass.
Change num_pages type to unsigned int.

In real life ballooning request come with num_pages in [512, 32768] range so
this is more a future-proof/cleanup.

Reported-by: Laszlo Ersek <lersek@...hat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Reviewed-by: Laszlo Ersek <lersek@...hat.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
---
 drivers/hv/hv_balloon.c |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 4052ad8..cb5b7dc 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1081,11 +1081,12 @@ static void free_balloon_pages(struct hv_dynmem_device *dm,
 
 
 
-static int alloc_balloon_pages(struct hv_dynmem_device *dm, int num_pages,
-			       struct dm_balloon_response *bl_resp,
-			       int alloc_unit)
+static unsigned int alloc_balloon_pages(struct hv_dynmem_device *dm,
+					unsigned int num_pages,
+					struct dm_balloon_response *bl_resp,
+					int alloc_unit)
 {
-	int i = 0;
+	unsigned int i = 0;
 	struct page *pg;
 
 	if (num_pages < alloc_unit)
@@ -1132,8 +1133,8 @@ static int alloc_balloon_pages(struct hv_dynmem_device *dm, int num_pages,
 
 static void balloon_up(struct work_struct *dummy)
 {
-	int num_pages = dm_device.balloon_wrk.num_pages;
-	int num_ballooned = 0;
+	unsigned int num_pages = dm_device.balloon_wrk.num_pages;
+	unsigned int num_ballooned = 0;
 	struct dm_balloon_response *bl_resp;
 	int alloc_unit;
 	int ret;
-- 
1.7.4.1

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