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Subject[PATCH 1/2] rbtree: fix postorder iteration when the rb_node is not the first element in an entry
Date
Provide a new helper called rb_next_postorder_entry() to perform NULL
checks and container_of() coversions and use it in
rbtree_for_each_entry_safe() to fix oopses that occur when rb_node is
not the first element in the entry.

Additionally, remove the missplaced NULL check from rb_next_postorder().

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
---
include/linux/rbtree.h | 20 +++++++++++++++-----
lib/rbtree.c | 2 --
2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h
index aa870a4..630eedb 100644
--- a/include/linux/rbtree.h
+++ b/include/linux/rbtree.h
@@ -86,6 +86,18 @@ static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
}

/**
+ * rb_next_postorder_entry - a helper to check for a NULL entry and advance to
+ * the next element.
+ *
+ * @elem: a 'type *' which is contained in an rbtree
+ * @field: the field in 'type' which contains the struct rb_node.
+ */
+#define rb_next_postorder_entry(elem, field) \
+ ((elem) ? rb_entry(rb_next_postorder(&(elem)->field), \
+ typeof(*(elem)), field) \
+ : NULL)
+
+/**
* rbtree_postorder_for_each_entry_safe - iterate over rb_root in post order of
* given type safe against removal of rb_node entry
*
@@ -96,11 +108,9 @@ static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
*/
#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
for (pos = rb_entry(rb_first_postorder(root), typeof(*pos), field),\
- n = rb_entry(rb_next_postorder(&pos->field), \
- typeof(*pos), field); \
- &pos->field; \
+ n = rb_next_postorder_entry(pos, field); \
+ pos; \
pos = n, \
- n = rb_entry(rb_next_postorder(&pos->field), \
- typeof(*pos), field))
+ n = rb_next_postorder_entry(pos, field))

#endif /* _LINUX_RBTREE_H */
diff --git a/lib/rbtree.c b/lib/rbtree.c
index 65f4eff..08168d0 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -534,8 +534,6 @@ static struct rb_node *rb_left_deepest_node(const struct rb_node *node)
struct rb_node *rb_next_postorder(const struct rb_node *node)
{
const struct rb_node *parent;
- if (!node)
- return NULL;
parent = rb_parent(node);

/* If we're sitting on node, we've already seen our children */
--
1.8.4.2


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