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

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Date: Tue, 19 Mar 2024 09:01:32 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Xu Yilun <yilun.xu@...ux.intel.com>
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 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.

thanks,

greg k-h