[PATCH v2] mm: fix incorrect pfn passed to untrack_pfn() in remap_pfn_range()

[Yongji Xie]

We use generic hooks in remap_pfn_range() to help archs to
track pfnmap regions. The code is something like:

int remap_pfn_range()
{
        ...
        track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
        ...
        pfn -= addr >> PAGE_SHIFT;
        ...
        untrack_pfn(vma, pfn, PAGE_ALIGN(size));
        ...
}

Here we can easily find the pfn is changed but not recovered
before untrack_pfn() is called. That's incorrect.

Signed-off-by: Yongji Xie <xyj...@linux.vnet.ibm.com>
---
 mm/memory.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 098f00d..eee75ed 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1711,6 +1711,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned 
long addr,
        unsigned long next;
        unsigned long end = addr + PAGE_ALIGN(size);
        struct mm_struct *mm = vma->vm_mm;
+       unsigned long remap_pfn = pfn;
        int err;
 
        /*
@@ -1737,7 +1738,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned 
long addr,
                vma->vm_pgoff = pfn;
        }
 
-       err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
+       err = track_pfn_remap(vma, &prot, remap_pfn, addr, PAGE_ALIGN(size));
        if (err)
                return -EINVAL;
 
@@ -1756,7 +1757,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned 
long addr,
        } while (pgd++, addr = next, addr != end);
 
        if (err)
-               untrack_pfn(vma, pfn, PAGE_ALIGN(size));
+               untrack_pfn(vma, remap_pfn, PAGE_ALIGN(size));
 
        return err;
 }
-- 
1.7.9.5