linux-kernel - [PATCH] mm: Fix incorrect pfn passed to untrack_pfn in remap_pfn

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Date:	Fri, 22 Apr 2016 18:31:28 +0800
From:	Yongji Xie <xyjxie@...ux.vnet.ibm.com>
To:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	jmarchan@...hat.com, mingo@...nel.org, vbabka@...e.cz,
	dave.hansen@...ux.intel.com, dan.j.williams@...el.com,
	matthew.r.wilcox@...el.com, aarcange@...hat.com, mhocko@...e.com,
	luto@...nel.org, dahi@...ux.vnet.ibm.com,
	Yongji Xie <xyjxie@...ux.vnet.ibm.com>
Subject: [PATCH] mm: Fix incorrect pfn passed to untrack_pfn in remap_pfn_range

We used 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 <xyjxie@...ux.vnet.ibm.com>
---
 mm/memory.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/memory.c b/mm/memory.c
index 098f00d..cb9e0c4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1755,6 +1755,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
 			break;
 	} while (pgd++, addr = next, addr != end);
 
+	pfn += (end - PAGE_ALIGN(size)) >> PAGE_SHIFT;
 	if (err)
 		untrack_pfn(vma, pfn, PAGE_ALIGN(size));
 
-- 
1.7.9.5