linux-kernel - Re: [PATCH] kfence: check kfence canary in panic and reboot

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Message-ID: <20220421134643.41728-1-huangshaobo6@huawei.com>
Date:   Thu, 21 Apr 2022 21:46:43 +0800
From:   Shaobo Huang <huangshaobo6@...wei.com>
To:     <elver@...gle.com>
CC:     <akpm@...ux-foundation.org>, <chenzefeng2@...wei.com>,
        <dvyukov@...gle.com>, <glider@...gle.com>,
        <huangshaobo6@...wei.com>, <kasan-dev@...glegroups.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <nixiaoming@...wei.com>, <wangbing6@...wei.com>,
        <wangfangpeng1@...wei.com>, <young.liuyang@...wei.com>,
        <zengweilin@...wei.com>, <zhongjubin@...wei.com>
Subject: Re: [PATCH] kfence: check kfence canary in panic and reboot

On Thu, 21 Apr 2022 15:28:45 +0200, Marco Elver <elver@...gle.com> wrote:
> On Thu, 21 Apr 2022 at 15:06, Alexander Potapenko <glider@...gle.com> wrote:
> [...]
> > This report will denote that in a system that could have been running for days a particular skbuff was corrupted by some unknown task at some unknown point in time.
> > How do we figure out what exactly caused this corruption?
> >
> > When we deploy KFENCE at scale, it is rarely possible for the kernel developer to get access to the host that reported the bug and try to reproduce it.
> > With that in mind, the report (plus the kernel source) must contain all the necessary information to address the bug, otherwise reporting it will result in wasting the developer's time.
> > Moreover, if we report such bugs too often, our tool loses the credit, which is hard to regain.
> 
> I second this - in particular we'll want this off in fuzzers etc.,
> because it'll just generate reports that nobody can use to debug an
> issue. I do see the value in this in potentially narrowing the cause
> of a panic, but that information is likely not enough to fully
> diagnose the root cause of the panic - it might however prompt to
> re-run with KASAN, or check if memory DIMMs are faulty etc.
> 
> We can still have this feature, but I suggest to make it
> off-by-default, and only enable via a boot param. I'd call it
> 'kfence.check_on_panic'. For your setup, you can then use it to enable
> where you see fit.

I agree to give users the option to use this feature.

> Thanks,
>-- Marco