+ mm-fix-potential-null-pointer-dereference.patch added to -mm tree

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Subject: + mm-fix-potential-null-pointer-dereference.patch added to -mm tree
To: huawei.libin@xxxxxxxxxx,kirill.shutemov@xxxxxxxxxxxxxxx,liwanp@xxxxxxxxxxxxxxxxxx,mhocko@xxxxxxx,stable@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 26 Jul 2013 14:39:41 -0700


The patch titled
     Subject: mm/huge_memory.c: fix potential NULL pointer dereference
has been added to the -mm tree.  Its filename is
     mm-fix-potential-null-pointer-dereference.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-fix-potential-null-pointer-dereference.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-potential-null-pointer-dereference.patch

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------------------------------------------------------
From: Libin <huawei.libin@xxxxxxxxxx>
Subject: mm/huge_memory.c: fix potential NULL pointer dereference

In collapse_huge_page() there is a race window between releasing the
mmap_sem read lock and taking the mmap_sem write lock, so find_vma() may
return NULL.  So check the return value to avoid NULL pointer dereference.

collapse_huge_page
	khugepaged_alloc_page
		up_read(&mm->mmap_sem)
	down_write(&mm->mmap_sem)
	vma = find_vma(mm, address)

Signed-off-by: Libin <huawei.libin@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v3.0+
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/huge_memory.c |    2 ++
 1 file changed, 2 insertions(+)

diff -puN mm/huge_memory.c~mm-fix-potential-null-pointer-dereference mm/huge_memory.c
--- a/mm/huge_memory.c~mm-fix-potential-null-pointer-dereference
+++ a/mm/huge_memory.c
@@ -2274,6 +2274,8 @@ static void collapse_huge_page(struct mm
 		goto out;
 
 	vma = find_vma(mm, address);
+	if (!vma)
+		goto out;
 	hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
 	hend = vma->vm_end & HPAGE_PMD_MASK;
 	if (address < hstart || address + HPAGE_PMD_SIZE > hend)
_

Patches currently in -mm which might be from huawei.libin@xxxxxxxxxx are

mm-fix-potential-null-pointer-dereference.patch

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