From: Alexander Potapenko <glider@xxxxxxxxxx> Subject: llist: introduce llist_entry_safe() Currently llist_for_each_entry() and llist_for_each_entry_safe() iterate until &pos->member != NULL. But when building the kernel with Clang, the compiler assumes &pos->member cannot be NULL if the member's offset is greater than 0. Therefore the loop condition is always true, and the loops become infinite. To work around this, introduce llist_entry_safe(), which returns NULL for NULL pointers, and additionally check that pos is not NULL in the list iterators before dereferencing it. Link: http://lkml.kernel.org/r/1474636978-41435-3-git-send-email-glider@xxxxxxxxxx Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Kostya Serebryany <kcc@xxxxxxxxxx> Cc: Eric Dumazet <edumazet@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/llist.h | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) diff -puN include/linux/llist.h~llist-introduce-llist_entry_safe include/linux/llist.h --- a/include/linux/llist.h~llist-introduce-llist_entry_safe +++ a/include/linux/llist.h @@ -88,6 +88,16 @@ static inline void init_llist_head(struc container_of(ptr, type, member) /** + * llist_entry_safe - get the struct of this entry without overflowing + * @ptr: the &struct llist_node pointer. + * @type: the type of the struct this is embedded in. + * @member: the name of the llist_node within the struct. + */ +#define llist_entry_safe(ptr, type, member) \ + container_of_safe(ptr, type, member) + + +/** * llist_for_each - iterate over some deleted entries of a lock-less list * @pos: the &struct llist_node to use as a loop cursor * @node: the first entry of deleted list entries @@ -120,9 +130,10 @@ static inline void init_llist_head(struc * reverse the order by yourself before traversing. */ #define llist_for_each_entry(pos, node, member) \ - for ((pos) = llist_entry((node), typeof(*(pos)), member); \ - &(pos)->member != NULL; \ - (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member)) + for ((pos) = llist_entry_safe((node), typeof(*(pos)), member); \ + pos != NULL && &(pos)->member != NULL; \ + (pos) = llist_entry_safe((pos)->member.next, \ + typeof(*(pos)), member)) /** * llist_for_each_entry_safe - iterate over some deleted entries of lock-less list of given type @@ -141,10 +152,11 @@ static inline void init_llist_head(struc * you want to traverse from the oldest to the newest, you must * reverse the order by yourself before traversing. */ -#define llist_for_each_entry_safe(pos, n, node, member) \ - for (pos = llist_entry((node), typeof(*pos), member); \ - &pos->member != NULL && \ - (n = llist_entry(pos->member.next, typeof(*n), member), true); \ +#define llist_for_each_entry_safe(pos, n, node, member) \ + for (pos = llist_entry_safe((node), typeof(*pos), member); \ + pos != NULL && &pos->member != NULL && \ + (n = llist_entry_safe(pos->member.next, typeof(*n), member), \ + true); \ pos = n) /** _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
