On Tue, Jun 23, 2020 at 10:09 AM Walter Wu <walter-zh.wu@xxxxxxxxxxxx> wrote: > > On Mon, 2020-06-01 at 13:08 +0800, Walter Wu wrote: > > This patchset improves KASAN reports by making them to have > > call_rcu() call stack information. It is useful for programmers > > to solve use-after-free or double-free memory issue. > > > > The KASAN report was as follows(cleaned up slightly): > > > > BUG: KASAN: use-after-free in kasan_rcu_reclaim+0x58/0x60 > > > > Freed by task 0: > > kasan_save_stack+0x24/0x50 > > kasan_set_track+0x24/0x38 > > kasan_set_free_info+0x18/0x20 > > __kasan_slab_free+0x10c/0x170 > > kasan_slab_free+0x10/0x18 > > kfree+0x98/0x270 > > kasan_rcu_reclaim+0x1c/0x60 > > > > Last call_rcu(): > > kasan_save_stack+0x24/0x50 > > kasan_record_aux_stack+0xbc/0xd0 > > call_rcu+0x8c/0x580 > > kasan_rcu_uaf+0xf4/0xf8 > > > > Generic KASAN will record the last two call_rcu() call stacks and > > print up to 2 call_rcu() call stacks in KASAN report. it is only > > suitable for generic KASAN. > > > > This feature considers the size of struct kasan_alloc_meta and > > kasan_free_meta, we try to optimize the structure layout and size > > , lets it get better memory consumption. > > > > [1]https://bugzilla.kernel.org/show_bug.cgi?id=198437 > > [2]https://groups.google.com/forum/#!searchin/kasan-dev/better$20stack$20traces$20for$20rcu%7Csort:date/kasan-dev/KQsjT_88hDE/7rNUZprRBgAJ > > > > Changes since v1: > > - remove new config option, default enable it in generic KASAN > > - test this feature in SLAB/SLUB, it is pass. > > - modify macro to be more clearly > > - modify documentation > > > > Changes since v2: > > - change recording from first/last to the last two call stacks > > - move free track into kasan free meta > > - init slab_free_meta on object slot creation > > - modify documentation > > > > Changes since v3: > > - change variable name to be more clearly > > - remove the redundant condition > > - remove init free meta-data and increasing object condition > > > > Changes since v4: > > - add a macro KASAN_KMALLOC_FREETRACK in order to check whether > > print free stack > > - change printing message > > - remove descriptions in Kocong.kasan > > > > Changes since v5: > > - reuse print_stack() in print_track() > > > > Changes since v6: > > - fix typo > > - renamed the variable name in testcase > > > > Walter Wu (4): > > rcu: kasan: record and print call_rcu() call stack > > kasan: record and print the free track > > kasan: add tests for call_rcu stack recording > > kasan: update documentation for generic kasan > > > > Hi Andrew, > > Would you tell me why don't pick up this patches? > Do I miss something? > > I will want to implement another new patches, but it need to depend on > this patches. On a related note. Doing this for workqueue on top of these patches may be useful as well, here is syzbot UAFs that mention process_one_work: https://groups.google.com/forum/#!searchin/syzkaller-bugs/%22use-after-free%22$20process_one_work%7Csort:date In some of these access/allocation happened in in process_one_work, in some workqueue queueing stack may not add much. But if we take the last one: https://groups.google.com/forum/#!searchin/syzkaller-bugs/%22use-after-free%22$20process_one_work%7Csort:date/syzkaller-bugs/IYE0kt0BZMQ/zNM5rlzjAQAJ It's exactly the same "free stack is useless" situation: Freed by task 17: kfree+0x10a/0x220 mm/slab.c:3757 process_one_work+0x76e/0xfd0 kernel/workqueue.c:2268 worker_thread+0xa7f/0x1450 kernel/workqueue.c:2414 kthread+0x353/0x380 kernel/kthread.c:268 The same may stand for times, I think I've seen some bugs where the bad access happens in the timer as well. Adding workqueue and timers should be pretty minimal change I think. > > Documentation/dev-tools/kasan.rst | 3 +++ > > include/linux/kasan.h | 2 ++ > > kernel/rcu/tree.c | 2 ++ > > lib/test_kasan.c | 30 ++++++++++++++++++++++++++++++ > > mm/kasan/common.c | 26 ++++---------------------- > > mm/kasan/generic.c | 43 +++++++++++++++++++++++++++++++++++++++++++ > > mm/kasan/generic_report.c | 1 + > > mm/kasan/kasan.h | 23 +++++++++++++++++++++-- > > mm/kasan/quarantine.c | 1 + > > mm/kasan/report.c | 54 +++++++++++++++++++++++++++--------------------------- > > mm/kasan/tags.c | 37 +++++++++++++++++++++++++++++++++++++ > > 11 files changed, 171 insertions(+), 51 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/1592899732.13735.8.camel%40mtksdccf07.
