Re: [PATCH 1/6] i2c: omap: Prevent NULL pointer dereference in remove

[Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

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On Thu, Aug 09, 2012 at 07:07:42PM +0530, Shubhrajyoti D wrote:
> Prevent the NULL pointer access by moving the platform_set_drvdata function
> after the access of the pdev.
> 
> [  654.961761] Unable to handle kernel NULL pointer dereference at virtual address 00000070
> [  654.970611] pgd = df254000
> [  654.973480] [00000070] *pgd=9f1da831, *pte=00000000, *ppte=00000000
> [  654.980163] Internal error: Oops: 17 [#1] SMP ARM
> [  654.985076] Modules linked in:
> [  654.988281] CPU: 1    Not tainted  (3.6.0-rc1-00031-ge547de1-dirty #339)
> [  654.995330] PC is at omap_i2c_runtime_resume+0x8/0x148
> [  655.000732] LR is at omap_i2c_runtime_resume+0x8/0x148
> 
> Signed-off-by: Shubhrajyoti D <shubhrajyoti-l0cyMroinI0@public.gmane.org>
> ---
>  drivers/i2c/busses/i2c-omap.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index c8e3886..0c593d4 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -1217,8 +1217,6 @@ static int __devexit omap_i2c_remove(struct platform_device *pdev)
>  	struct omap_i2c_dev	*dev = platform_get_drvdata(pdev);
>  	int ret;
>  
> -	platform_set_drvdata(pdev, NULL);
> -
>  	i2c_del_adapter(&dev->adapter);
>  	ret = pm_runtime_get_sync(&pdev->dev);
>  	if (IS_ERR_VALUE(ret))
> @@ -1227,6 +1225,8 @@ static int __devexit omap_i2c_remove(struct platform_device *pdev)
>  	omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, 0);
>  	pm_runtime_put(&pdev->dev);
>  	pm_runtime_disable(&pdev->dev);
> +	platform_set_drvdata(pdev, NULL);
> +
>  	return 0;
>  }

I think this patch is correct, because drvdata is used in the PM code of
the driver and thus cleared too early.

As such, this is a bugfix and should be not based on the big cleanup
since it should go into this rc series.

I will pick it as soon as the comments on the other patches are
answered.

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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