>From d51a16626d241ded8913768d6f24484b1d4335ba Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 5 Nov 2013 21:39:48 +0100 Subject: [PATCH] rbtree: Fix rbtree_postorder_for_each_entry_safe() iterator The iterator rbtree_postorder_for_each_entry_safe() relies on pointer underflow behavior when testing for loop termination. In particular it expects that &rb_entry(NULL, type, field)->field is NULL. But the result of this expression is not defined by a C standard and some gcc versions (e.g. 4.3.4) assume the above expression can never be equal to NULL. The net result is an oops because the iteration is not properly terminated. Fix the problem by modifying the iterator to avoid pointer underflows. Signed-off-by: Jan Kara --- include/linux/rbtree.h | 16 +++++++++------- 1 files changed, 9 insertions(+), 7 deletions(-) diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h index aa870a4..57e75ae 100644 --- a/include/linux/rbtree.h +++ b/include/linux/rbtree.h @@ -85,6 +85,11 @@ static inline void rb_link_node(struct rb_node * node, struct rb_node * parent, *rb_link = node; } +#define rb_entry_safe(ptr, type, member) \ + ({ typeof(ptr) ____ptr = (ptr); \ + ____ptr ? rb_entry(____ptr, type, member) : NULL; \ + }) + /** * rbtree_postorder_for_each_entry_safe - iterate over rb_root in post order of * given type safe against removal of rb_node entry @@ -95,12 +100,9 @@ static inline void rb_link_node(struct rb_node * node, struct rb_node * parent, * @field: the name of the rb_node field within 'type'. */ #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; \ - pos = n, \ - n = rb_entry(rb_next_postorder(&pos->field), \ - typeof(*pos), field)) + for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \ + pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \ + typeof(*pos), field); 1; }); \ + pos = n) #endif /* _LINUX_RBTREE_H */ -- 1.6.0.2