linux-kernel - Re: [PATCH v2] lockdep: Allow tuning tracing capacity constants.

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Message-ID: <0f7233f7-a04a-e9c9-7920-3a170cc97e4b@i-love.sakura.ne.jp>
Date:   Sat, 5 Sep 2020 01:05:30 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v2] lockdep: Allow tuning tracing capacity constants.

Hello. Can we apply this patch?

This patch addresses top crashers for syzbot, and applying this patch
will help utilizing syzbot's resource for finding other bugs.

On 2020/08/28 0:20, 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].
> 
> Let's allow individually tuning upper limits via kernel config options
> (based on an assumption that there is no inter-dependency among these
> constants).
> 
> [1] https://syzkaller.appspot.com/bug?id=3d97ba93fb3566000c1c59691ea427370d33ea1b
> [2] https://syzkaller.appspot.com/bug?id=381cb436fe60dc03d7fd2a092b46d7f09542a72a
> [3] https://syzkaller.appspot.com/bug?id=a588183ac34c1437fc0785e8f220e88282e5a29f
> 
> Reported-by: syzbot <syzbot+cd0ec5211ac07c18c049@...kaller.appspotmail.com>
> Reported-by: syzbot <syzbot+91fd909b6e62ebe06131@...kaller.appspotmail.com>
> Reported-by: syzbot <syzbot+62ebe501c1ce9a91f68c@...kaller.appspotmail.com>
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> ---
>  kernel/locking/lockdep.c           |  2 +-
>  kernel/locking/lockdep_internals.h |  8 +++---
>  lib/Kconfig.debug                  | 40 ++++++++++++++++++++++++++++++
>  3 files changed, 45 insertions(+), 5 deletions(-)
>