[PATCH 4.4 35/50] x86/mm: Fix slow_virt_to_phys() for X86_PAE again

Greg Kroah-Hartman
2016-03-14T18:14:29Z

From: Dexuan Cui <decui@microsoft.com>

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.

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: 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -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;
}