linux-kernel - [PATCH 3.12 041/111] lguest: fix out-by-one error in address checking.

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Message-Id: <cbcba3e43dc6f8b2643c4a098e55e75e4df413b8.1433943052.git.jslaby@suse.cz>
Date:	Wed, 10 Jun 2015 17:26:30 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 041/111] lguest: fix out-by-one error in address checking.

From: Rusty Russell <rusty@...tcorp.com.au>

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

===============

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@...tcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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);
 }
 
 /*
-- 
2.4.2

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