[3.16.y-ckt extended stable] Patch "x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE" has been added to staging queue

[Luis Henriques]

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

    x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE

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?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt1.

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 cafa9442b4891496d9afcf4dd5e48e364c93ddaf Mon Sep 17 00:00:00 2001
From: Dexuan Cui <decui at microsoft.com>
Date: Wed, 29 Oct 2014 03:53:37 -0700
Subject: x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE

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 at microsoft.com>
Cc: K. Y. Srinivasan <kys at microsoft.com>
Cc: Haiyang Zhang <haiyangz at microsoft.com>
Cc: gregkh at linuxfoundation.org
Cc: linux-mm at kvack.org
Cc: olaf at aepfle.de
Cc: apw at canonical.com
Cc: jasowang at redhat.com
Cc: dave.hansen at intel.com
Cc: riel at redhat.com
Link: http://lkml.kernel.org/r/1414580017-27444-1-git-send-email-decui@microsoft.com
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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 ae242a7c11c7..36de293caf25 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -409,7 +409,7 @@ 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);
--
2.1.0