On Mon, 2020-08-10 at 19:50 +0800, Walter Wu wrote: > On Mon, 2020-08-10 at 07:19 -0400, Qian Cai wrote: > > > > > On Aug 10, 2020, at 3:21 AM, Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > > > > > Syzbot reports many UAF issues for workqueue or timer, see [1] and [2]. > > > In some of these access/allocation happened in process_one_work(), > > > we see the free stack is useless in KASAN report, it doesn't help > > > programmers to solve UAF on workqueue. The same may stand for times. > > > > > > This patchset improves KASAN reports by making them to have workqueue > > > queueing stack and timer queueing stack information. It is useful for > > > programmers to solve use-after-free or double-free memory issue. > > > > > > Generic KASAN will record the last two workqueue and timer stacks, > > > print them in KASAN report. It is only suitable for generic KASAN. > > > > > > In order to print the last two workqueue and timer stacks, so that > > > we add new members in struct kasan_alloc_meta. > > > - two workqueue queueing work stacks, total size is 8 bytes. > > > - two timer queueing stacks, total size is 8 bytes. > > > > > > Orignial struct kasan_alloc_meta size is 16 bytes. After add new > > > members, then the struct kasan_alloc_meta total size is 32 bytes, > > > It is a good number of alignment. Let it get better memory consumption. > > > > Getting debugging tools complicated surely is the best way to kill it. I would argue that it only make sense to complicate it if it is useful most of the time which I never feel or hear that is the case. This reminds me your recent call_rcu() stacks that most of time just makes parsing the report cumbersome. Thus, I urge this exercise to over-engineer on special cases need to stop entirely. > > > > A good debug tool is to have complete information in order to solve > issue. We should focus on if KASAN reports always show this debug > information or create a option to decide if show it. Because this > feature is Dmitry's suggestion. see [1]. So I think it need to be > implemented. Maybe we can wait his response. > > [1]https://lkml.org/lkml/2020/6/23/256 > > Thanks. > Fix name typo. I am sorry to him. And add a bugzilla to show why need to do it. please see [1]. [1] https://bugzilla.kernel.org/show_bug.cgi?id=198437 > > > > > > [1]https://groups.google.com/g/syzkaller-bugs/search?q=%22use-after-free%22+process_one_work > > > [2]https://groups.google.com/g/syzkaller-bugs/search?q=%22use-after-free%22%20expire_timers > > > [3]https://bugzilla.kernel.org/show_bug.cgi?id=198437 > > > > > > Walter Wu (5): > > > timer: kasan: record and print timer stack > > > workqueue: kasan: record and print workqueue stack > > > lib/test_kasan.c: add timer test case > > > lib/test_kasan.c: add workqueue test case > > > kasan: update documentation for generic kasan > > > > > > Documentation/dev-tools/kasan.rst | 4 ++-- > > > include/linux/kasan.h | 4 ++++ > > > kernel/time/timer.c | 2 ++ > > > kernel/workqueue.c | 3 +++ > > > lib/test_kasan.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > mm/kasan/generic.c | 42 ++++++++++++++++++++++++++++++++++++++++++ > > > mm/kasan/kasan.h | 6 +++++- > > > mm/kasan/report.c | 22 ++++++++++++++++++++++ > > > 8 files changed, 134 insertions(+), 3 deletions(-) > > > > > > -- > > > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > > > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx. > > > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20200810072115.429-1-walter-zh.wu%40mediatek.com. >
