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SubjectRe: [PATCH RESEND] spi: erase pointer to drvdata on removal
On Mon, Dec 3, 2012 at 8:28 PM, Vivien Didelot
<vivien.didelot@savoirfairelinux.com> wrote:
> Without this patch, a SPI device may keep its drvdata whereas it was unbound
> from its driver. This may result in accessing an invalid pointer.
>
> As for i2c-core, let the SPI core handle the removal of the device's drvdata,
> after a remove(), or a probe() failure.
>
> This is a resent of the previous patch https://lkml.org/lkml/2012/11/1/314
>
> Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>

Are you seeing a real bug without this patch? If so, then that is a
driver bug. I don't want to mask over bugs silently. The kernel should
complain.

There are actually lots of things that drivers should/should-not do
that could be checked by the probe/remove hooks, and not just in the
SPI code. spi_set_drvdata() is actually just a wrapper around
dev_set_drvdata().

Instead of clearing the pointer only in the spi code, perhaps the
checks should be in really_probe() and __device_release_driver() so it
covers all bus types. Also, don't clear the pointer. Just use
dev_err() to report on the driver bug so that it gets fixed properly.

g.

> ---
> drivers/spi/spi.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 84c2861..fe636fe 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -233,15 +233,25 @@ EXPORT_SYMBOL_GPL(spi_bus_type);
> static int spi_drv_probe(struct device *dev)
> {
> const struct spi_driver *sdrv = to_spi_driver(dev->driver);
> + struct spi_device *sdev = to_spi_device(dev);
> + int status;
>
> - return sdrv->probe(to_spi_device(dev));
> + status = sdrv->probe(sdev);
> + if (status)
> + spi_set_drvdata(sdev, NULL);
> + return status;
> }
>
> static int spi_drv_remove(struct device *dev)
> {
> const struct spi_driver *sdrv = to_spi_driver(dev->driver);
> + struct spi_device *sdev = to_spi_device(dev);
> + int status;
>
> - return sdrv->remove(to_spi_device(dev));
> + status = sdrv->remove(sdev);
> + if (status == 0)
> + spi_set_drvdata(sdev, NULL);
> + return status;
> }
>
> static void spi_drv_shutdown(struct device *dev)
> --
> 1.7.11.7
>
> --
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--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.


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