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 @@ -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) _ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html