[PATCH 4/6] mm, hwpoison: fix possible use-after-free in mf_dax_kill_procs()

[Miaohe Lin <linmiaohe@huawei.com>]

After kill_procs(), tk will be freed without being removed from the to_kill
list. In the next iteration, the freed list entry in the to_kill list will
be accessed, thus leading to use-after-free issue. Fix it by reinitializing
the to_kill list after unmap_and_kill().

Fixes: c36e20249571 ("mm: introduce mf_dax_kill_procs() for fsdax case")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 mm/memory-failure.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 7023c3d81273..a2f4e8b00a26 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1658,6 +1658,8 @@ int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
 		collect_procs_fsdax(page, mapping, index, &to_kill);
 		unmap_and_kill(&to_kill, page_to_pfn(page), mapping,
 				index, mf_flags);
+		/* Reinitialize to_kill list for later resuing. */
+		INIT_LIST_HEAD(&to_kill);
 unlock:
 		dax_unlock_mapping_entry(mapping, index, cookie);
 	}
-- 
2.23.0