Messages in this thread |  | | Subject | Re: [PATCH v3] lockdep: Allow tuning tracing capacity constants. | From | Tetsuo Handa <> | Date | Wed, 18 Nov 2020 22:57:08 +0900 |
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Peter, do you have a plan to make this problem actionable?
On 2020/10/18 22:02, Tetsuo Handa wrote: > Peter, what do you think? Can we apply this patch? > > A potential for-now workaround for syzkaller would be to allow syzkaller > not to encounter the BUG: message (by masking BUG: message on the kernel > side) when hitting these limits, for continue testing until the kernel > crashes (due to other bugs like UAF) would be to some degree useful. > > On 2020/10/10 21:58, Tetsuo Handa wrote: >> Since syzkaller continues various test cases until the kernel crashes, >> syzkaller tends to examine more locking dependencies than normal systems. >> As a result, syzbot is reporting that the fuzz testing was terminated >> due to hitting upper limits lockdep can track [1] [2] [3]. >> >> Peter Zijlstra does not want to allow tuning these limits via kernel >> config options, for such change discourages thinking. But currently we >> are not actionable, for lockdep does not report the culprit for hitting >> these limits [4]. >> >> Therefore, I propose this patch again, with a caveat that this patch is >> expected to be reverted after lockdep becomes capable of reporting the >> culprit, for I consider that "postpone fixing lock related problems in >> existing code" is less painful than "not detecting lock related problems >> introduced by new patches". >> >> [1] https://syzkaller.appspot.com/bug?id=3d97ba93fb3566000c1c59691ea427370d33ea1b >> [2] https://syzkaller.appspot.com/bug?id=381cb436fe60dc03d7fd2a092b46d7f09542a72a >> [3] https://syzkaller.appspot.com/bug?id=a588183ac34c1437fc0785e8f220e88282e5a29f >> [4] https://lkml.kernel.org/r/CACT4Y+agTiEF-1i9LbAgp-q_02oYF0kAPZGAAJ==-wx2Xh7xzQ@mail.gmail.com >> >> Reported-by: syzbot <syzbot+cd0ec5211ac07c18c049@syzkaller.appspotmail.com> >> Reported-by: syzbot <syzbot+91fd909b6e62ebe06131@syzkaller.appspotmail.com> >> Reported-by: syzbot <syzbot+62ebe501c1ce9a91f68c@syzkaller.appspotmail.com> >> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> >> Acked-by: Dmitry Vyukov <dvyukov@google.com> >> --- >> kernel/locking/lockdep.c | 2 +- >> kernel/locking/lockdep_internals.h | 8 +++--- >> lib/Kconfig.debug | 40 ++++++++++++++++++++++++++++++ >> 3 files changed, 45 insertions(+), 5 deletions(-)
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