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==-wx2xh7...@mail.gmail.com > > Reported-by: syzbot <syzbot+cd0ec5211ac07c18c...@syzkaller.appspotmail.com> > Reported-by: syzbot <syzbot+91fd909b6e62ebe06...@syzkaller.appspotmail.com> > Reported-by: syzbot <syzbot+62ebe501c1ce9a91f...@syzkaller.appspotmail.com> > Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> > Acked-by: Dmitry Vyukov <dvyu...@google.com> > --- > kernel/locking/lockdep.c | 2 +- > kernel/locking/lockdep_internals.h | 8 +++--- > lib/Kconfig.debug | 40 ++++++++++++++++++++++++++++++ > 3 files changed, 45 insertions(+), 5 deletions(-)
