linux-kernel - [PATCH 3.12 070/206] x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86

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Message-Id: <0833c9e835508b7dc0305846e8b2ebf793a18d97.1416319692.git.jslaby@suse.cz>
Date:	Tue, 18 Nov 2014 15:07:05 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Dexuan Cui <decui@...rosoft.com>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	gregkh@...uxfoundation.org, linux-mm@...ck.org, olaf@...fle.de,
	apw@...onical.com, jasowang@...hat.com, dave.hansen@...el.com,
	riel@...hat.com, Thomas Gleixner <tglx@...utronix.de>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 070/206] x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE

From: Dexuan Cui <decui@...rosoft.com>

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

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

commit d1cd1210834649ce1ca6bafe5ac25d2f40331343 upstream.

pte_pfn() returns a PFN of long (32 bits in 32-PAE), so "long <<
PAGE_SHIFT" will overflow for PFNs above 4GB.

Due to this issue, some Linux 32-PAE distros, running as guests on Hyper-V,
with 5GB memory assigned, can't load the netvsc driver successfully and
hence the synthetic network device can't work (we can use the kernel parameter
mem=3000M to work around the issue).

Cast pte_pfn() to phys_addr_t before shifting.

Fixes: "commit d76565344512: x86, mm: Create slow_virt_to_phys()"
Signed-off-by: Dexuan Cui <decui@...rosoft.com>
Cc: K. Y. Srinivasan <kys@...rosoft.com>
Cc: Haiyang Zhang <haiyangz@...rosoft.com>
Cc: gregkh@...uxfoundation.org
Cc: linux-mm@...ck.org
Cc: olaf@...fle.de
Cc: apw@...onical.com
Cc: jasowang@...hat.com
Cc: dave.hansen@...el.com
Cc: riel@...hat.com
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/1414580017-27444-1-git-send-email-decui@microsoft.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/x86/mm/pageattr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index bb32480c2d71..aabdf762f592 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -389,7 +389,7 @@ phys_addr_t slow_virt_to_phys(void *__virt_addr)
 	psize = page_level_size(level);
 	pmask = page_level_mask(level);
 	offset = virt_addr & ~pmask;
-	phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
+	phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
 	return (phys_addr | offset);
 }
 EXPORT_SYMBOL_GPL(slow_virt_to_phys);
-- 
2.1.3

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