From: Jan Kara <[email protected]> Subject: 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 <[email protected]> Signed-off-by: Cody P Schafer <[email protected]> Cc: Michel Lespinasse <[email protected]> Cc: "David S. Miller" <[email protected]> Cc: Adrian Hunter <[email protected]> Cc: Artem Bityutskiy <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Jozsef Kadlecsik <[email protected]> Cc: Pablo Neira Ayuso <[email protected]> Cc: Patrick McHardy <[email protected]> Cc: Paul Mundt <[email protected]> Cc: Theodore Ts'o <[email protected]> Cc: <[email protected]> [3.12.x] Signed-off-by: Andrew Morton <[email protected]> --- include/linux/rbtree.h | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff -puN include/linux/rbtree.h~rbtree-fix-rbtree_postorder_for_each_entry_safe-iterator include/linux/rbtree.h --- a/include/linux/rbtree.h~rbtree-fix-rbtree_postorder_for_each_entry_safe-iterator +++ a/include/linux/rbtree.h @@ -85,6 +85,11 @@ static inline void rb_link_node(struct r *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 r * @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 */ _ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
