radix-tree: Fix UBSAN warning

get_slot_offset() can be called with a NULL 'parent' argument.
In this case, the calculated value will not be used, but calculating
it is undefined.  Rather than fixing the caller (__radix_tree_delete)
to not call get_slot_offset(), make get_slot_offset() robust against
being called with a NULL parent.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index a9e41aed6de4bfb063af9d16d41942a041a23fdd..cc6096b97afbb7be8611b9369411172fca2a1d94 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -120,7 +120,7 @@ bool is_sibling_entry(const struct radix_tree_node *parent, void *node)
 static inline unsigned long
 get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
 {
-       return slot - parent->slots;
+       return parent ? slot - parent->slots : 0;
 }
 
 static unsigned int radix_tree_descend(const struct radix_tree_node *parent,