linux-kernel - Re: [PATCH 2/2] scsi: ufs: Protect PM ops and err

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Date:   Tue, 12 Jan 2021 08:45:29 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Bean Huo <huobean@...il.com>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, ziqichen@...eaurora.org,
        rnayak@...eaurora.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com,
        rjw@...ysocki.net, Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Nitin Rawat <nitirawa@...eaurora.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Bart Van Assche <bvanassche@....org>,
        Satya Tangirala <satyat@...gle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] scsi: ufs: Protect PM ops and err_handler from user
 access through sysfs

On 2021-01-11 18:04, Bean Huo wrote:
> On Mon, 2021-01-11 at 17:22 +0800, Can Guo wrote:
>> > > meaning you are tring to access a register when clocks are
>> > > disabled.
>> > > This
>> > > leads to system CRASH.
>> > >
>> >
>> > OK, let it simple, share this kind of crash log becuase of access
>> > sysfs
>> > node in the shutdown flow.
>> >
>> >
>> > > [2] OCP is over current protection. While UFS shutting down, you
>> > > may
>> > > have put UFS regulators to LPM. After that, if you are still
>> > > trying
>> > > to
>> > > talk to UFS, OCP can happen on VCCQ/VCCQ2. This leads to system
>> > > CRASH
>> > > too.
>> >
>> > the same as above, share the crash log.
>> >
>> 
>> If you have hand-on experiences on NoC and/or OCP issues, you won't
>> ask
>> for the crash log. The tricky parts about critial NoC and OCP issues
>> is
> 
> OK, interesting. would you tell me which register access node in ufs-
> sysfs.c can trigger this crash? let me verify your statement.
> 
> 

I believe I have explained enough to prove we need this change.

If you are really interested in NoC and OCP, feel free to ping me
on teams, I will show you how to trigger one and what is it like
on my setup.

Can Guo.

> Bean
> 
>>