linux-kernel - Re: [PATCH 1/3] phy: qcom-qmp-usb: fix NULL pointer dereference in PM callbacks

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Message-ID: <sxqgnmj4bawj7n6kan7tiutb5ynhxz6cgbtpbz2xx4ixodtdw6@q2ftbnpjouvb>
Date: Mon, 25 Aug 2025 21:50:30 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
Cc: Vinod Koul <vkoul@...nel.org>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Dmitry Baryshkov <lumag@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, Poovendhan Selvaraj <quic_poovendh@...cinc.com>, 
	stable@...r.kernel.org
Subject: Re: [PATCH 1/3] phy: qcom-qmp-usb: fix NULL pointer dereference in
 PM callbacks

On Mon, Aug 25, 2025 at 05:22:02PM +0530, Kathiravan Thirumoorthy wrote:
> From: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
> 
> The pm ops are enabled before qmp phy create which causes
> a NULL pointer dereference when accessing qmp->phy->init_count
> in the qmp_usb_runtime_suspend.
> 

How does that happen? Do we end up in the error path inbetween the
devm_pm_runtime_enable()? Or does it happen by some other means?

This would be quite useful information for others to know if they hit
the same or just a similar problem.

> So if qmp->phy is NULL, bail out early in suspend / resume callbacks
> to avoid the NULL pointer dereference in qmp_usb_runtime_suspend and
> qmp_usb_runtime_resume.
> 
> Below is the stacktrace for reference:
> 
> [<818381a0>] (qmp_usb_runtime_suspend [phy_qcom_qmp_usb]) from [<4051d1d8>] (__rpm_callback+0x3c/0x110)
> [<4051d1d8>] (__rpm_callback) from [<4051d2fc>] (rpm_callback+0x50/0x54)
> [<4051d2fc>] (rpm_callback) from [<4051d940>] (rpm_suspend+0x23c/0x428)
> [<4051d940>] (rpm_suspend) from [<4051e808>] (pm_runtime_work+0x74/0x8c)
> [<4051e808>] (pm_runtime_work) from [<401311f4>] (process_scheduled_works+0x1d0/0x2c8)
> [<401311f4>] (process_scheduled_works) from [<40131d48>] (worker_thread+0x260/0x2e4)
> [<40131d48>] (worker_thread) from [<40138970>] (kthread+0x118/0x12c)
> [<40138970>] (kthread) from [<4010013c>] (ret_from_fork+0x14/0x38)
> 
> Cc: stable@...r.kernel.org # v6.0
> Fixes: 65753f38f530 ("phy: qcom-qmp-usb: drop multi-PHY support")

Has this been a reproducible issue for last 3 years? I think the fixes
makes sense in that it introduced the indirection, but when did the
issue actually show up?

Regards,
Bjorn

> Signed-off-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
> Signed-off-by: Kathiravan Thirumoorthy <kathiravan.thirumoorthy@....qualcomm.com>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-usb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-usb.c b/drivers/phy/qualcomm/phy-qcom-qmp-usb.c
> index ed646a7e705ba3259708775ed5fedbbbada13735..cd04e8f22a0fe81b086b308d02713222aa95cae3 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-usb.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-usb.c
> @@ -1940,7 +1940,7 @@ static int __maybe_unused qmp_usb_runtime_suspend(struct device *dev)
>  
>  	dev_vdbg(dev, "Suspending QMP phy, mode:%d\n", qmp->mode);
>  
> -	if (!qmp->phy->init_count) {
> +	if (!qmp->phy || !qmp->phy->init_count) {
>  		dev_vdbg(dev, "PHY not initialized, bailing out\n");
>  		return 0;
>  	}
> @@ -1960,7 +1960,7 @@ static int __maybe_unused qmp_usb_runtime_resume(struct device *dev)
>  
>  	dev_vdbg(dev, "Resuming QMP phy, mode:%d\n", qmp->mode);
>  
> -	if (!qmp->phy->init_count) {
> +	if (!qmp->phy || !qmp->phy->init_count) {
>  		dev_vdbg(dev, "PHY not initialized, bailing out\n");
>  		return 0;
>  	}
> 
> -- 
> 2.34.1
>