[RFC PATCH] mm: truncate: flush lru cache for evicted inode

[Hillf Danton]

Flush lru cache to avoid folio->mapping uaf in case of inode teardown.

Reported-and-tested-by: syzbot+d79afb004be235636ee8@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Hillf Danton <hdanton@xxxxxxxx>
---
Post for comments because lru_add_drain_all() is too haevy a hammer.

--- x/mm/truncate.c
+++ y/mm/truncate.c
@@ -419,6 +419,9 @@ void truncate_inode_pages_range(struct a
 		truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
 		folio_batch_release(&fbatch);
 	}
+
+	if (mapping_exiting(mapping))
+		lru_add_drain_all();
 }
 EXPORT_SYMBOL(truncate_inode_pages_range);
 
--