Commit d778ca56 authored by Libin's avatar Libin Committed by Greg Kroah-Hartman

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: default avatarLibin <huawei.libin@huawei.com>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: default avatarWanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5a20c03a
......@@ -1894,6 +1894,8 @@ 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)
......
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