[3.16.y-ckt stable] Patch "lguest: fix out-by-one error in address checking." has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    lguest: fix out-by-one error in address checking.

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt13.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 69fb957fba08004ea732164bd45d933fb3bfdc31 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty at rustcorp.com.au>
Date: Wed, 27 May 2015 10:59:26 +0930
Subject: lguest: fix out-by-one error in address checking.

commit 83a35114d0e4583e6b0ca39502e68b6a92e2910c upstream.

This bug has been there since day 1; addresses in the top guest physical
page weren't considered valid.  You could map that page (the check in
check_gpte() is correct), but if a guest tried to put a pagetable there
we'd check that address manually when walking it, and kill the guest.

Signed-off-by: Rusty Russell <rusty at rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/lguest/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index 0bf1e4edf04d..19da22249bd8 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -176,7 +176,7 @@ static void unmap_switcher(void)
 bool lguest_address_ok(const struct lguest *lg,
 		       unsigned long addr, unsigned long len)
 {
-	return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
+	return addr+len <= lg->pfn_limit * PAGE_SIZE && (addr+len >= addr);
 }

 /*