In this discuss[1], linus proposed a idea to solve the use-after-iter problem caused by the inappropriate iterator variable use of list_for_each_entry* macros *outside* the loop. The core of the idea is that make the rule be "you never use the iterator outside the loop". The perfect way should be "you are prohibited by the compiler from using iterator variable outside the loop". Thus, we can declare the iterator variable inside the loop and any use of iterator outside the loop will be report as a error by compiler. "declare the iterator variable inside the *for* loop" needs something above gnu89 (like -std=gnu11), which is the task of PATCH 1. The core patch of this series is PATCH 2, which respectively implements a new iterator-inside macro for each list_for_each_entry* macro (10 variants). The name of the new macro is suffixed with *_inside*, such as list_for_each_entry_inside for list_for_each_entry. The reason for a new macro instead of directly modification on origin macro is that, there are 15000+ callers of there macros scattered in the whole kernel code. We cannot change all of these correctly in one single patch considering that it must be correct for each commit. Thus, we can define a new macro, and incrementally change these callers until all these in the kernel are completely updated with *_inside* one. At that time, we can just remove the implements of origin macros and rename the *_inside* macro back to the origin name just in one single patch. The PATCH 3~6 demonstrate how to change list_for_each_entry* callers into *_inside one. Note all these 4 patch are just to prove the effectiveness of the scheme for each list_for_each_entry* macro (10 variants). I think the reasonable way is to kill all these 15000+ callers *on a file basis*, considering that different macros may be called in the same context and depend on each other, instead of *on a separate macro basis*. [1]: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@xxxxxxxxxxxxxx/ Xiaomeng Tong (6): Kbuild: compile kernel with gnu11 std list: add new MACROs to make iterator invisiable outside the loop kernel: remove iterator use outside the loop mm: remove iterator use outside the loop net/core: remove iterator use outside the loop drivers/dma: remove iterator use outside the loop Makefile | 2 +- drivers/dma/iop-adma.c | 9 +-- include/linux/list.h | 156 ++++++++++++++++++++++++++++++++++++++++ kernel/power/snapshot.c | 28 ++++---- kernel/signal.c | 6 +- mm/list_lru.c | 10 +-- mm/slab_common.c | 7 +- mm/vmalloc.c | 6 +- net/core/gro.c | 3 +- 9 files changed, 191 insertions(+), 36 deletions(-) -- 2.17.1
