rmap: fix anon_vma_fork() memory leak

Fix a memory leak in anon_vma_fork(), where we fail to tear down the
anon_vmas attached to the new VMA in case setting up the new anon_vma
fails.

This bug also has the potential to leave behind anon_vma_chain structs
with pointers to invalid memory.

Reported-by: Minchan Kim <[email protected]>
Signed-off-by: Rik van Riel <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/rmap.c b/mm/rmap.c
index fcd593c9..eaa7a09 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -232,6 +232,7 @@
  out_error_free_anon_vma:
 	anon_vma_free(anon_vma);
  out_error:
+	unlink_anon_vmas(vma);
 	return -ENOMEM;
 }