mm: prevent derefencing NULL ptr in pfn_section_valid()
[ Upstream commit 82f0b6f041fad768c28b4ad05a683065412c226e ]
Commit 5ec8e8ea8b77 ("mm/sparsemem: fix race in accessing
memory_section->usage") changed pfn_section_valid() to add a READ_ONCE()
call around "ms->usage" to fix a race with section_deactivate() where
ms->usage can be cleared. The READ_ONCE() call, by itself, is not enough
to prevent NULL pointer dereference. We need to check its value before
dereferencing it.
Link: https://lkml.kernel.org/r/[email protected]
Fixes: 5ec8e8ea8b77 ("mm/sparsemem: fix race in accessing memory_section->usage")
Signed-off-by: Waiman Long <[email protected]>
Cc: Charan Teja Kalla <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
1 file changed
