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authorLibin <huawei.libin@huawei.com>2013-09-11 14:20:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-11 15:57:19 -0700
commita8f531ebc33052642b4bd7b812eedf397108ce64 (patch)
treeeed956b9a3e7efa02937d984ae3f8d94810a478d /mm/huge_memory.c
parente2d0bd2b924d74d5e0d4f395f8f4730d125e198c (diff)
downloadlinux-a8f531ebc33052642b4bd7b812eedf397108ce64.tar.bz2
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@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> Cc: <stable@vger.kernel.org> # v3.0+ Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
-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 8b7fc2025e04..963e14c0486f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2296,6 +2296,8 @@ 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)