From: Libin <[email protected]>
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 <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Wanpeng Li <[email protected]>
Reviewed-by: Michal Hocko <[email protected]>
Cc: <[email protected]> # v3.0+
Signed-off-by: Andrew Morton <[email protected]>
---
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
@@ -2296,6 +2296,8 @@ 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)
_
--
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