On Thu, Mar 21, 2019 at 10:45 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > > 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 And to make things even more interesting, this later changes to "BUG: unable to handle kernel NULL pointer dereference in vb2_vmalloc_put": testing release v4.12 testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c with gcc (GCC) 8.1.0 all runs: crashed: general protection fault in refcount_sub_and_test testing release v4.11 testing commit a351e9b9fc24e982ec2f0e76379a49826036da12 with gcc (GCC) 7.3.0 all runs: crashed: BUG: unable to handle kernel NULL pointer dereference in vb2_vmalloc_put And since the original bug is in vb2 subsystem (https://syzkaller.appspot.com/bug?id=17535f4bf5b322437f7c639b59161ce343fc55a9), it's actually not clear even for me, if we should treat it as the same bug or not. May be different manifestation of the same root cause, or a different bug around. > 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;
