[patch 026/162] mm: fix incorrect pfn passed to untrack_pfn() in remap_pfn_range()

[akpm@xxxxxxxxxxxxxxxxxxxx]

From: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
Subject: mm: fix incorrect pfn passed to untrack_pfn() in remap_pfn_range()

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.

There are no known runtime effects - this is from inspection.

Signed-off-by: Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Jerome Marchand <jmarchan@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/memory.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff -puN mm/memory.c~mm-fix-incorrect-pfn-passed-to-untrack_pfn-in-remap_pfn_range-v2 mm/memory.c
--- a/mm/memory.c~mm-fix-incorrect-pfn-passed-to-untrack_pfn-in-remap_pfn_range-v2
+++ a/mm/memory.c
@@ -1744,6 +1744,7 @@ int remap_pfn_range(struct vm_area_struc
 	unsigned long next;
 	unsigned long end = addr + PAGE_ALIGN(size);
 	struct mm_struct *mm = vma->vm_mm;
+	unsigned long remap_pfn = pfn;
 	int err;
 
 	/*
@@ -1770,7 +1771,7 @@ int remap_pfn_range(struct vm_area_struc
 		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;
 
@@ -1789,7 +1790,7 @@ int remap_pfn_range(struct vm_area_struc
 	} 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;
 }
_
--
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