linux-kernel - pm_runtime_resume_and_get in .remove callbacks

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Date:   Wed, 13 Jul 2022 10:47:39 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: pm_runtime_resume_and_get in .remove callbacks

Hello,

there is a big bunch of kernel drivers (here:
drivers/i2c/busses/i2c-sprd.c) that have a remove callback that looks as
follows:

	static int sprd_i2c_remove(struct platform_device *pdev)
	{
		struct sprd_i2c *i2c_dev = platform_get_drvdata(pdev);
		int ret;

		ret = pm_runtime_resume_and_get(i2c_dev->dev);
		if (ret < 0)
			return ret;

		i2c_del_adapter(&i2c_dev->adap);
		clk_disable_unprepare(i2c_dev->clk);

		pm_runtime_put_noidle(i2c_dev->dev);
		pm_runtime_disable(i2c_dev->dev);

		return 0;
	}

If pm_runtime_resume_and_get fails, the i2c adapter isn't removed, but
as the memory backing i2c_dev goes away---it was allocated using
devm_kzalloc in .probe()---the next i2c action will probably access
freed memory.

I'm not familiar enough with pm-runtime stuff, but wonder what
can/should be done about that. The obvious (to me) candidates are:

 - log an error if pm_runtime_resume_and_get() fails, but continue to
   clean up
 - don't check the return value at all

What do you think?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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