Patch "x86/mm: Fix slow_virt_to_phys() for X86_PAE again" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

x86/mm: Fix slow_virt_to_phys() for X86_PAE again

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     x86-mm-fix-slow_virt_to_phys-for-x86_pae-again.patch

and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dexuan Cui <[email protected]>
Date: Thu, 25 Feb 2016 01:58:12 -0800
Subject: x86/mm: Fix slow_virt_to_phys() for X86_PAE again

From: Dexuan Cui <[email protected]>

commit bf70e5513dfea29c3682e7eb3dbb45f0723bac09 upstream.

"d1cd12108346: x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE" was unintentionally removed by the recent "34437e67a672: x86/mm: Fix slow_virt_to_phys() to handle large PAT bit".

And, the variable 'phys_addr' was defined as "unsigned long" by mistake -- it should be "phys_addr_t".

As a result, Hyper-V network driver in 32-PAE Linux guest can't work again.

---
 arch/x86/mm/pageattr.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

@@ -414,24 +414,30 @@ pmd_t *lookup_pmd_address(unsigned long
 phys_addr_t slow_virt_to_phys(void *__virt_addr)
 {
 	unsigned long virt_addr = (unsigned long)__virt_addr;
-	unsigned long phys_addr, offset;
+	phys_addr_t phys_addr;
+	unsigned long offset;
 	enum pg_level level;
 	pte_t *pte;
 
 	pte = lookup_address(virt_addr, &level);
 	BUG_ON(!pte);
 
+	/*
+	 * pXX_pfn() returns unsigned long, which must be cast to phys_addr_t
+	 * before being left-shifted PAGE_SHIFT bits -- this trick is to
+	 * make 32-PAE kernel work correctly.
+	 */
 	switch (level) {
 	case PG_LEVEL_1G:
-		phys_addr = pud_pfn(*(pud_t *)pte) << PAGE_SHIFT;
+		phys_addr = (phys_addr_t)pud_pfn(*(pud_t *)pte) << PAGE_SHIFT;
 		offset = virt_addr & ~PUD_PAGE_MASK;
 		break;
 	case PG_LEVEL_2M:
-		phys_addr = pmd_pfn(*(pmd_t *)pte) << PAGE_SHIFT;
+		phys_addr = (phys_addr_t)pmd_pfn(*(pmd_t *)pte) << PAGE_SHIFT;
 		offset = virt_addr & ~PMD_PAGE_MASK;
 		break;
 	default:
-		phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
+		phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
 		offset = virt_addr & ~PAGE_MASK;
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/x86-mm-fix-slow_virt_to_phys-for-x86_pae-again.patch