x86/mm: Fix slow_virt_to_phys() for X86_PAE again

"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.

Fixes: commit 34437e67a672: "x86/mm: Fix slow_virt_to_phys() to handle large PAT bit"
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Cc: olaf@aepfle.de
Cc: gregkh@linuxfoundation.org
Cc: jasowang@redhat.com
Cc: driverdev-devel@linuxdriverproject.org
Cc: linux-mm@kvack.org
Cc: apw@canonical.com
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Link: http://lkml.kernel.org/r/1456394292-9030-1-git-send-email-decui@microsoft.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 10 insertions, 4 deletions

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 2440814b0069..9cf96d82147a 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -419,24 +419,30 @@ pmd_t *lookup_pmd_address(unsigned long address)
 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;
         }