> 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. > > [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.
