[patch] NULL pointer check for vma->vm_mm

["Kenichi Okuyama" <kenichi.okuyama@gmail.com>]

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Dear all,

I was looking at the ./mm/rmap.c .. I found that, in function
"page_referenced_one()",
   struct mm_struct *mm = vma->vm_mm;
was being refererred without NULL check.

Though I do agree that this works for most of the cases, I thought it
is better to add
BUG_ON() for case of mm being NULL.

attached is the patch for this

thank you in advance for taking your time.
best regards,
-- 
(Kenichi Okuyama)
URL: http://www.dd.iij4u.or.jp/~okuyamak/

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--- ./mm/rmap.c.orig	2008-02-01 15:36:50.000000000 +0900
+++ ./mm/rmap.c	2008-02-01 15:42:43.000000000 +0900
@@ -276,6 +276,8 @@ static int page_referenced_one(struct pa
 	spinlock_t *ptl;
 	int referenced = 0;
 
+	BUG_ON(( mm == NULL ));
+
 	address = vma_address(page, vma);
 	if (address == -EFAULT)
 		goto out;