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authorLibin <huawei.libin@huawei.com>2013-09-11 14:20:38 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-09-26 17:18:28 -0700
commit8b89ae8a4914ee393c0db530735d933481272e97 (patch)
tree34995383309c09b7495068c62d5b72c855575e77
parentd96fa17975d6b1d1dd1264170ccdfabb254f71c2 (diff)
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 <huawei.libin@huawei.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--mm/huge_memory.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 362c329b83f..b92d0ce428b 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2286,6 +2286,8 @@ 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)