From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, Dmitry Vyukov <dvyukov@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v3] lockdep: Allow tuning tracing capacity constants.
Date: Wed, 18 Nov 2020 22:57:08 +0900 [thread overview]
Message-ID: <81ab0ffd-6e80-c96c-053a-b1b4fe8694c1@i-love.sakura.ne.jp> (raw)
In-Reply-To: <6933e938-f219-5e13-aee6-fe4de87eb43e@i-love.sakura.ne.jp>
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(-)
next prev parent reply other threads:[~2020-11-18 13:58 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-25 1:30 [PATCH] lockdep: Introduce CONFIG_LOCKDEP_LARGE Tetsuo Handa
2020-07-25 4:48 ` Dmitry Vyukov
2020-07-25 5:23 ` Tetsuo Handa
2020-08-04 2:36 ` Tetsuo Handa
2020-08-18 9:57 ` Dmitry Vyukov
2020-08-18 11:07 ` Tetsuo Handa
2020-08-18 12:02 ` Dmitry Vyukov
2020-08-18 12:59 ` Tetsuo Handa
2020-08-27 15:20 ` [PATCH v2] lockdep: Allow tuning tracing capacity constants Tetsuo Handa
2020-09-04 16:05 ` Tetsuo Handa
2020-09-16 11:28 ` Dmitry Vyukov
2020-09-16 11:50 ` peterz
2020-09-16 12:14 ` Dmitry Vyukov
2020-09-28 0:24 ` Tetsuo Handa
2020-09-28 5:12 ` Dmitry Vyukov
2020-10-10 12:58 ` [PATCH v3] " Tetsuo Handa
2020-10-18 13:02 ` Tetsuo Handa
2020-11-18 13:57 ` Tetsuo Handa [this message]
2020-11-18 14:23 ` Peter Zijlstra
2020-11-18 14:30 ` Tetsuo Handa
2020-11-18 15:10 ` Peter Zijlstra
2020-11-18 15:31 ` Tetsuo Handa
2020-11-19 12:33 ` Dmitry Vyukov
2020-11-19 12:43 ` Dmitry Vyukov
2020-11-19 12:49 ` Dmitry Vyukov
2020-11-19 13:06 ` Dmitry Vyukov
2020-11-19 13:45 ` Tetsuo Handa
2020-11-19 14:05 ` Dmitry Vyukov
[not found] ` <CACT4Y+aNJmuhk0KicX4FzKW6PhawFBgvrC2gSJcWwUkR8VSSmg@mail.gmail.com>
2020-11-19 14:36 ` Dmitry Vyukov
2020-11-19 18:08 ` Dmitry Vyukov
2020-11-20 9:22 ` Dmitry Vyukov
2020-11-20 9:27 ` Dmitry Vyukov
2020-11-22 1:56 ` Tetsuo Handa
2020-11-27 9:00 ` Dmitry Vyukov
2020-12-03 13:47 ` Tetsuo Handa
2020-12-04 14:35 ` Tetsuo Handa
2020-11-19 14:57 ` Tetsuo Handa
2021-01-01 8:09 ` [PATCH v4] " Tetsuo Handa
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