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

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Message-ID: <ZfkOvXslEjgU+fc1@yilunxu-OptiPlex-7050>
Date: Tue, 19 Mar 2024 12:04:13 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: Marco Pagani <marpagan@...hat.com>
Cc: 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>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	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 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