[PATCH 6/8] lib/ext2fs/kernel-list.h: Fix undefined behavior in list_entry() macro

[Sami Liedes <sami.liedes@iki.fi>]

Fix the macro, which is essentially a copy of the container_of() in
the kernel, to use offsetof instead of a null pointer dereference.

Caught by clang -fsanitize=undefined.

Signed-off-by: Sami Liedes <sami.liedes@iki.fi>
---
 lib/ext2fs/kernel-list.h |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/ext2fs/kernel-list.h b/lib/ext2fs/kernel-list.h
index e07d06b..85ae213 100644
--- a/lib/ext2fs/kernel-list.h
+++ b/lib/ext2fs/kernel-list.h
@@ -103,8 +103,10 @@ static __inline__ void list_splice(struct list_head *list, struct list_head *hea
 	}
 }
 
-#define list_entry(ptr, type, member) \
-	((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
+#define list_entry(ptr, type, member) ({                      \
+       const typeof( ((type *)0)->member ) *__mptr = (ptr);   \
+       (type *)( (char *)__mptr - offsetof(type,member) );})
+
 
 #define list_for_each(pos, head) \
         for (pos = (head)->next; pos != (head); pos = pos->next)
-- 
1.7.10.4