On 25.12.2021 17:10:46, Uwe Kleine-König wrote:
> The current implementation gets device lifetime tracking wrong. The
> problem is that allocation of struct counter_device is controlled by the
> individual drivers but this structure contains a struct device that
> might have to live longer than a driver is bound. As a result a command
> sequence like:
>
> { sleep 5; echo bang; } > /dev/counter0 &
> sleep 1;
> echo 40000000.timer:counter > /sys/bus/platform/drivers/stm32-timer-counter/unbind
>
> can keep a reference to the struct device and unbinding results in
> freeing the memory occupied by this device resulting in an oops.
>
> This commit provides two new functions (plus some helpers):
> - counter_alloc() to allocate a struct counter_device that is
> automatically freed once the embedded struct device is released
> - counter_add() to register such a device.
>
> Note that this commit doesn't fix any issues, all drivers have to be
> converted to these new functions to correct the lifetime problems.
>
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> ---
> drivers/counter/counter-core.c | 149 ++++++++++++++++++++++++++++++++-
> include/linux/counter.h | 15 ++++
> 2 files changed, 163 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
> index 00c41f28c101..17a93e6c018a 100644
> --- a/drivers/counter/counter-core.c
> +++ b/drivers/counter/counter-core.c
> @@ -15,6 +15,7 @@
> #include <linux/kdev_t.h>
> #include <linux/module.h>
> #include <linux/mutex.h>
> +#include <linux/slab.h>
> #include <linux/types.h>
> #include <linux/wait.h>
>
> @@ -24,6 +25,11 @@
> /* Provides a unique ID for each counter device */
> static DEFINE_IDA(counter_ida);
>
> +struct counter_device_allochelper {
> + struct counter_device counter;
> + unsigned long privdata[0];
> +};
Is this a use case for DECLARE_FLEX_ARRAY()?
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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