Re: [PATCH v2 1/6] phy: core: Fix that API devm_phy_put() fails to release the phy

From: Johan Hovold <johan@kernel.org>
To: Zijun Hu <zijun_hu@icloud.com>
Cc: "Vinod Koul" <vkoul@kernel.org>,
	"Kishon Vijay Abraham I" <kishon@kernel.org>,
	"Felipe Balbi" <balbi@ti.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Rob Herring" <robh@kernel.org>, "Arnd Bergmann" <arnd@arndb.de>,
	"Lee Jones" <lee@kernel.org>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Christophe JAILLET" <christophe.jaillet@wanadoo.fr>,
	stable@vger.kernel.org, linux-phy@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	"Zijun Hu" <quic_zijuhu@quicinc.com>
Subject: Re: [PATCH v2 1/6] phy: core: Fix that API devm_phy_put() fails to release the phy
Date: Tue, 29 Oct 2024 14:40:01 +0100	[thread overview]
Message-ID: <ZyDlsWaA5aiRa_ry@hovoldconsulting.com> (raw)
In-Reply-To: <20241024-phy_core_fix-v2-1-fc0c63dbfcf3@quicinc.com>

On Thu, Oct 24, 2024 at 10:39:26PM +0800, Zijun Hu wrote:
> From: Zijun Hu <quic_zijuhu@quicinc.com>
> 
> For devm_phy_put(), its comment says it needs to invoke phy_put() to
> release the phy, but it does not invoke the function actually since
> devres_destroy() will not call devm_phy_release() at all which will
> call the function, and the missing phy_put() call will cause:

Please split the above up in at least two sentences to make it easier to
parse. Split it after devm_phy_release() and rephrase the latter part
(e.g. by dropping "at all which will call the function").

> - 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();
> 
>   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
> 
> Fixes: ff764963479a ("drivers: phy: add generic PHY framework")
> Cc: stable@vger.kernel.org
> Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Cc: "Krzysztof Wilczyński" <kw@linux.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>

Diff itself looks good. Nice find.

Johan

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