linux-kernel - Re: [PATCH v6] fpga: manager: add owner module and take its refcount

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Message-ID: <ZfomC4W8f6id5gRa@yilunxu-OptiPlex-7050>
Date: Wed, 20 Mar 2024 07:55:55 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Marco Pagani <marpagan@...hat.com>, Moritz Fischer <mdf@...nel.org>,
	Wu Hao <hao.wu@...el.com>, Xu Yilun <yilun.xu@...el.com>,
	Tom Rix <trix@...hat.com>, Jonathan Corbet <corbet@....net>,
	Alan Tull <atull@...nsource.altera.com>,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-fpga@...r.kernel.org
Subject: Re: [PATCH v6] fpga: manager: add owner module and take its refcount

On Tue, Mar 19, 2024 at 09:01:32AM +0100, Greg Kroah-Hartman wrote:
> On Tue, Mar 19, 2024 at 12:04:13PM +0800, Xu Yilun wrote:
> > On Tue, Mar 05, 2024 at 08:29:26PM +0100, Marco Pagani wrote:
> > > The current implementation of the fpga manager assumes that the low-level
> > > module registers a driver for the parent device and uses its owner pointer
> > > to take the module's refcount. This approach is problematic since it can
> > > lead to a null pointer dereference while attempting to get the manager if
> > > the parent device does not have a driver.
> > > 
> > > To address this problem, add a module owner pointer to the fpga_manager
> > > struct and use it to take the module's refcount. Modify the functions for
> > > registering the manager to take an additional owner module parameter and
> > > rename them to avoid conflicts. Use the old function names for helper
> > > macros that automatically set the module that registers the manager as the
> > > owner. This ensures compatibility with existing low-level control modules
> > > and reduces the chances of registering a manager without setting the owner.
> > > 
> > > Also, update the documentation to keep it consistent with the new interface
> > > for registering an fpga manager.
> > > 
> > > Other changes: opportunistically move put_device() from __fpga_mgr_get() to
> > > fpga_mgr_get() and of_fpga_mgr_get() to improve code clarity since the
> > > manager device is taken in these functions.
> > > 
> > > Fixes: 654ba4cc0f3e ("fpga manager: ensure lifetime with of_fpga_mgr_get")
> > > Suggested-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Suggested-by: Xu Yilun <yilun.xu@...el.com>
> > > Signed-off-by: Marco Pagani <marpagan@...hat.com>
> > 
> > Acked-by: Xu Yilun <yilun.xu@...el.com>
> > 
> > Will apply to v6.9-rc1
> 
> It is way too late for -rc1, sorry, this needs to wait for the next
> release.

You're right. I'm sorry, I mean I will apply when v6.9-rc1 comes.

> 
> thanks,
> 
> greg k-h