linux-kernel - Re: [PATCH] i2c: exynos5: Init data before registering interrupt handler

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Message-ID: <20240304161557.GS30969@axis.com>
Date: Mon, 4 Mar 2024 17:15:57 +0100
From: Jesper Nilsson <jesper.nilsson@...s.com>
To: Andi Shyti <andi.shyti@...nel.org>
CC: Jesper Nilsson <jesper.nilsson@...s.com>, Krzysztof Kozlowski
	<krzysztof.kozlowski@...aro.org>, Alim Akhtar <alim.akhtar@...sung.com>,
	<linux-i2c@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-samsung-soc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel@...s.com>
Subject: Re: [PATCH] i2c: exynos5: Init data before registering interrupt
 handler

On Mon, Mar 04, 2024 at 04:04:08PM +0100, Andi Shyti wrote:
> Hi Jesper,

Hi Andi,

> On Mon, Mar 04, 2024 at 12:01:14PM +0100, Jesper Nilsson wrote:
> > devm_request_irq() is called before we initialize the "variant"
> > member variable from of_device_get_match_data(), so if an interrupt
> > is triggered inbetween, we can end up following a NULL pointer
> > in the interrupt handler.
> > 
> > This problem was exposed when the I2C controller in question was
> > (mis)configured to be used in both secure world and Linux.
> > 
> > That this can happen is also reflected by the existing code that
> > clears any pending interrupts from "u-boot or misc causes".
> > 
> > Move the clearing of pending interrupts and the call to
> > devm_request_irq() to the end of probe.
> 
> I'm OK with moving the irq request at the end and I'm going to
> give my r-b anyway. There is still one comment below.

Thanks.

> > Additionally, return failure if we can't find a match in devicetree.
> > 
> > Signed-off-by: Jesper Nilsson <jesper.nilsson@...s.com>
> 
> The way you are describing it you would need the Fixes tag here
> and this patch should be treated as a fix.

Ok, the variant member was introduced in:

218e1496135e ("i2c: exynos5: add support for HSI2C on Exynos5260 SoC")

Before that, the ordering didn't matter.

> Nevertheless, I think that it's odd that the device is sending
> interrupts at this phase and the real fix should be preventing
> the controller to send interrupts here.

I found this bug when we moved control of an I2C bus into secure
world (OP-TEE) and hadn't removed it from devicetree config.
Since we hadn't enabled the secure parts yet, the kernel could still get
the interrupt, even when OP-TEE was performing I2C transfers.

> How have you tested this patch?

This was tested in our ARTPEC-8 SoC, which includes the same IP the
exynos SoCs, both with and without the problematic configuration
described above.

> > ---
> >  drivers/i2c/busses/i2c-exynos5.c | 32 ++++++++++++++++++--------------
> >  1 file changed, 18 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-exynos5.c b/drivers/i2c/busses/i2c-exynos5.c
> > index 385ef9d9e4d4..eba717e5cad7 100644
> > --- a/drivers/i2c/busses/i2c-exynos5.c
> > +++ b/drivers/i2c/busses/i2c-exynos5.c
> > @@ -906,24 +906,14 @@ static int exynos5_i2c_probe(struct platform_device *pdev)
> >  	i2c->adap.algo_data = i2c;
> >  	i2c->adap.dev.parent = &pdev->dev;
> >  
> > -	/* Clear pending interrupts from u-boot or misc causes */
> > -	exynos5_i2c_clr_pend_irq(i2c);
> > -
> >  	spin_lock_init(&i2c->lock);
> >  	init_completion(&i2c->msg_complete);
> >  
> > -	i2c->irq = ret = platform_get_irq(pdev, 0);
> > -	if (ret < 0)
> > -		goto err_clk;
> > -
> > -	ret = devm_request_irq(&pdev->dev, i2c->irq, exynos5_i2c_irq,
> > -			       IRQF_NO_SUSPEND, dev_name(&pdev->dev), i2c);
> > -	if (ret != 0) {
> > -		dev_err(&pdev->dev, "cannot request HS-I2C IRQ %d\n", i2c->irq);
> > -		goto err_clk;
> > -	}
> > -
> >  	i2c->variant = of_device_get_match_data(&pdev->dev);
> > +	if (!i2c->variant) {
> > +		dev_err(&pdev->dev, "can't match device variant\n");
> > +		return -ENODEV;
> 
> return dev_err_probe(), please.

Will do.

> Andi

/^JN - Jesper Nilsson
-- 
               Jesper Nilsson -- jesper.nilsson@...s.com