linux-kernel - Re: [PATCH v4 1/6] phy: core: Fix that API devm_phy

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Message-ID: <ZypSPb7qSR9zYSFv@hovoldconsulting.com>
Date: Tue, 5 Nov 2024 18:13:33 +0100
From: Johan Hovold <johan@...nel.org>
To: Zijun Hu <zijun_hu@...oud.com>
Cc: Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Lee Jones <lee@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	stable@...r.kernel.org, linux-phy@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH v4 1/6] phy: core: Fix that API devm_phy_put() fails to
 release the phy

On Sat, Nov 02, 2024 at 11:53:43AM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@...cinc.com>
> 
> For devm_phy_put(), its comment says it needs to invoke phy_put() to
> release the phy, but it will not actually invoke the function since
> devres_destroy() does not call devm_phy_release(), and the missing
> phy_put() call will cause:

I still think the above should have been split in two sentences, but
this also works.

> - The phy fails to be released.
> - devm_phy_put() can not fully undo what API devm_phy_get() does.
> - Leak refcount of both the module and device for below typical usage:
> 
>   devm_phy_get(); // or its variant
>   ...
>   err = do_something();
>   if (err)
>       goto err_out;
>   ...
>   err_out:
>   devm_phy_put(); // leak refcount here
> 
>   The file(s) affected by this issue are shown below since they have such
>   typical usage.
>   drivers/pci/controller/cadence/pcie-cadence.c
>   drivers/net/ethernet/ti/am65-cpsw-nuss.c
> 
> Fixed by using devres_release() instead of devres_destroy() within the API.

Nit: in the future, try to use imperative mood in your commit messages
(e.g. "fix" instead of "fixed") as the process documentation suggests.

> Fixes: ff764963479a ("drivers: phy: add generic PHY framework")
> Cc: stable@...r.kernel.org
> Cc: Lorenzo Pieralisi <lpieralisi@...nel.org>
> Cc: "Krzysztof Wilczyński" <kw@...ux.com>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: Johan Hovold <johan@...nel.org>
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>

Reviewed-by: Johan Hovold <johan+linaro@...nel.org>