linux-kernel - [PATCH v2] mm: fix incorrect pfn passed to untrack_pfn() in remap_pfn

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Message-Id: <1461470501-5044-1-git-send-email-xyjxie@linux.vnet.ibm.com>
Date:	Sun, 24 Apr 2016 12:01:41 +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 v2] 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.

Signed-off-by: Yongji Xie <xyjxie@...ux.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