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References: <20230628105250.40874-1-dg573847474@gmail.com> <2023062851-gutter-rudder-5c2d@gregkh>
In-Reply-To: <2023062851-gutter-rudder-5c2d@gregkh>
From:   Chengfeng Ye <dg573847474@gmail.com>
Date:   Wed, 28 Jun 2023 19:32:32 +0800
Message-ID: <CAAo+4rX5nJo63ZF64d3rf7_QC+1pR+-EBH7_5JrsrJn1nhpkfQ@mail.gmail.com>
Subject: Re: [PATCH] misc: bcm_vk: Fix potential deadlock on &vk->ctx_lock
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     scott.branden@broadcom.com, bcm-kernel-feedback-list@broadcom.com,
        arnd@arndb.de, linux-kernel@vger.kernel.org
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Thanks for the reply! V2 patch is sent including more detail of the static
analyzer and testing process.

Best Regards,
Chengfeng

Greg KH <gregkh@linuxfoundation.org> =E4=BA=8E2023=E5=B9=B46=E6=9C=8828=E6=
=97=A5=E5=91=A8=E4=B8=89 19:00=E5=86=99=E9=81=93=EF=BC=9A
>
> On Wed, Jun 28, 2023 at 10:52:50AM +0000, Chengfeng Ye wrote:
> > As &vk->ctx_lock is acquired by timer bcm_vk_hb_poll() under softirq
> > context, other process context code should disable irq or bottom-half
> > before acquire the same lock, otherwise deadlock could happen if the
> > timer preempt the execution while the lock is held in process context
> > on the same CPU.
> >
> > Possible deadlock scenario
> > bcm_vk_open()
> >     -> bcm_vk_get_ctx()
> >     -> spin_lock(&vk->ctx_lock)
> >         <timer iterrupt>
> >         -> bcm_vk_hb_poll()
> >         -> bcm_vk_blk_drv_access()
> >         -> spin_lock_irqsave(&vk->ctx_lock, flags) (deadlock here)
> >
> > This flaw was found using an experimental static analysis tool we are
> > developing for irq-related deadlock.
> >
> > The tentative patch fix the potential deadlock by spin_lock_irqsave().
>
> how was this tested?  As per the file,
> Documentation/process/researcher-guidelines.rst, you have to show this.
>
> thanks,
>
> greg k-h