On Wed, Mar 20, 2019 at 2:57 PM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > > On Wed, Mar 20, 2019 at 2:33 PM Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> wrote: > > > > > > > > On 3/20/19 1:38 PM, Dmitry Vyukov wrote: > > > On Wed, Mar 20, 2019 at 11:24 AM Tetsuo Handa > > > <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > > >> > > >> On 2019/03/20 18:59, Dmitry Vyukov wrote: > > >>>> From bisection log: > > >>>> > > >>>> testing release v4.17 > > >>>> testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0 > > >>>> run #0: crashed: kernel panic: corrupted stack end in wb_workfn > > >>>> run #1: crashed: kernel panic: corrupted stack end in worker_thread > > >>>> run #2: crashed: kernel panic: Out of memory and no killable processes... > > >>>> run #3: crashed: kernel panic: corrupted stack end in wb_workfn > > >>>> run #4: crashed: kernel panic: corrupted stack end in wb_workfn > > >>>> run #5: crashed: kernel panic: corrupted stack end in wb_workfn > > >>>> run #6: crashed: kernel panic: corrupted stack end in wb_workfn > > >>>> run #7: crashed: kernel panic: corrupted stack end in wb_workfn > > >>>> run #8: crashed: kernel panic: Out of memory and no killable processes... > > >>>> run #9: crashed: kernel panic: corrupted stack end in wb_workfn > > >>>> testing release v4.16 > > >>>> testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda with gcc (GCC) 8.1.0 > > >>>> run #0: OK > > >>>> run #1: OK > > >>>> run #2: OK > > >>>> run #3: OK > > >>>> run #4: OK > > >>>> run #5: crashed: kernel panic: Out of memory and no killable processes... > > >>>> run #6: OK > > >>>> run #7: crashed: kernel panic: Out of memory and no killable processes... > > >>>> run #8: OK > > >>>> run #9: OK > > >>>> testing release v4.15 > > >>>> testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff with gcc (GCC) 8.1.0 > > >>>> all runs: OK > > >>>> # git bisect start v4.16 v4.15 > > >>>> > > >>>> Why bisect started between 4.16 4.15 instead of 4.17 4.16? > > >>> > > >>> Because 4.16 was still crashing and 4.15 was not crashing. 4.15..4.16 > > >>> looks like the right range, no? > > >> > > >> No, syzbot should bisect between 4.16 and 4.17 regarding this bug, for > > >> "Stack corruption" can't manifest as "Out of memory and no killable processes". > > >> > > >> "kernel panic: Out of memory and no killable processes..." is completely > > >> unrelated to "kernel panic: corrupted stack end in wb_workfn". > > > > > > > > > Do you think this predicate is possible to code? > > > > Something like bellow probably would work better than current behavior. > > > > For starters, is_duplicates() might just compare 'crash' title with 'target_crash' title and its duplicates titles. > > Lots of bugs (half?) manifest differently. On top of this, titles > change as we go back in history. On top of this, if we see a different > bug, it does not mean that the original bug is also not there. > This will sure solve some subset of cases better then the current > logic. But I feel that that subset is smaller then what the current > logic solves. Counter-examples come up in basically every other bisection. For example: bisecting cause commit starting from ccda4af0f4b92f7b4c308d3acc262f4a7e3affad building syzkaller on 5f5f6d14e80b8bd6b42db961118e902387716bcb testing commit ccda4af0f4b92f7b4c308d3acc262f4a7e3affad with gcc (GCC) 8.1.0 all runs: crashed: KASAN: null-ptr-deref Read in refcount_sub_and_test_checked testing release v4.19 testing commit 84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d with gcc (GCC) 8.1.0 all runs: crashed: KASAN: null-ptr-deref Read in refcount_sub_and_test_checked testing release v4.18 testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703 with gcc (GCC) 8.1.0 all runs: crashed: KASAN: null-ptr-deref Read in refcount_sub_and_test testing release v4.17 testing commit 29dcea88779c856c7dc92040a0c01233263101d4 with gcc (GCC) 8.1.0 all runs: crashed: KASAN: null-ptr-deref Read in refcount_sub_and_test That's a different crash title, unless somebody explicitly code this case. Or, what crash is this? testing commit 52358cb5a310990ea5069f986bdab3620e01181f with gcc (GCC) 8.1.0 run #1: crashed: general protection fault in cpuacct_charge run #2: crashed: WARNING: suspicious RCU usage in corrupted run #3: crashed: general protection fault in cpuacct_charge run #4: crashed: BUG: unable to handle kernel paging request in ipt_do_table run #5: crashed: KASAN: stack-out-of-bounds Read in cpuacct_charge run #6: crashed: WARNING: suspicious RCU usage run #7: crashed: no output from test machine run #8: crashed: no output from test machine Or, that "INFO: trying to register non-static key in can_notifier" does not do any testing, but is "WARNING in dma_buf_vunmap" still there or not? testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c with gcc (GCC) 8.1.0 all runs: crashed: WARNING in dma_buf_vunmap testing release v4.11 testing commit a351e9b9fc24e982ec2f0e76379a49826036da12 with gcc (GCC) 7.3.0 all runs: OK # git bisect start v4.12 v4.11 Bisecting: 7831 revisions left to test after this (roughly 13 steps) [2bd80401743568ced7d303b008ae5298ce77e695] Merge tag 'gpio-v4.12-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio testing commit 2bd80401743568ced7d303b008ae5298ce77e695 with gcc (GCC) 7.3.0 all runs: crashed: INFO: trying to register non-static key in can_notifier # git bisect bad 2bd80401743568ced7d303b008ae5298ce77e695 Bisecting: 3853 revisions left to test after this (roughly 12 steps) [8d65b08debc7e62b2c6032d7fe7389d895b92cbc] Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next testing commit 8d65b08debc7e62b2c6032d7fe7389d895b92cbc with gcc (GCC) 7.3.0 all runs: crashed: INFO: trying to register non-static key in can_notifier # git bisect bad 8d65b08debc7e62b2c6032d7fe7389d895b92cbc Bisecting: 2022 revisions left to test after this (roughly 11 steps) [cec381919818a9a0cb85600b3c82404bdd38cf36] Merge tag 'mac80211-next-for-davem-2017-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next testing commit cec381919818a9a0cb85600b3c82404bdd38cf36 with gcc (GCC) 5.5.0 all runs: crashed: INFO: trying to register non-static key in can_notifier > > syzbot has some knowledge about duplicates with different crash titles when people use "syz dup" command. > > This is very limited set of info. And in the end I think we've seen > all bug types being duped on all other bugs types pair-wise, and at > the same time we've seen all bug types being not dups to all other bug > types. So I don't see where this gets us. > And again as we go back in history all these titles change. > > > Also it might be worth to experiment with using neural networks to identify duplicates. > > > > > > target_crash = 'kernel panic: corrupted stack end in wb_workfn' > > test commit: > > bad = false; > > skip = true; > > foreach run: > > run_started, crashed, crash := run_repro(); > > > > //kernel built, booted, reproducer launched successfully > > if (run_started) > > skip = false; > > if (crashed && is_duplicates(crash, target_crash)) > > bad = true; > > > > if (skip) > > git bisect skip; > > else if (bad) > > git bisect bad; > > else > > git bisect good;
