From 56cbe7f7ee88a2eb06226ab3b5b4333fe0df663f Mon Sep 17 00:00:00 2001 From: Libin Date: Wed, 11 Sep 2013 14:20:38 -0700 Subject: mm/huge_memory.c: fix potential NULL pointer dereference commit a8f531ebc33052642b4bd7b812eedf397108ce64 upstream. 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 Acked-by: Kirill A. Shutemov Reviewed-by: Wanpeng Li Reviewed-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- mm/huge_memory.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'mm') diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d80ac4bb0971..ed0ed8a41fba 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1882,6 +1882,8 @@ static void collapse_huge_page(struct mm_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) -- cgit v1.2.3