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SubjectRe: [PATCH] driver core: bus: Handle early calls to bus_to_subsys()
On Tue, Feb 21, 2023 at 01:53:51PM +0100, Geert Uytterhoeven wrote:
> When calling soc_device_match() from early_initcall(), bus_kset is still
> NULL, causing a crash:
>
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000028
> ...
> Call trace:
> __lock_acquire+0x530/0x20f0
> lock_acquire.part.0+0xc8/0x210
> lock_acquire+0x64/0x80
> _raw_spin_lock+0x4c/0x60
> bus_to_subsys+0x24/0xac
> bus_for_each_dev+0x30/0xcc
> soc_device_match+0x4c/0xe0
> r8a7795_sysc_init+0x18/0x60
> rcar_sysc_pd_init+0xb0/0x33c
> do_one_initcall+0x128/0x2bc
>
> Before, bus_for_each_dev() handled this gracefully by checking that
> the back-pointer to the private structure was valid.
>
> Fix this by adding a NULL check for bus_kset to bus_to_subsys().
>
> Fixes: 83b9148df2c95e23 ("driver core: bus: bus iterator cleanups")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> drivers/base/bus.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index cfe8615d5106f030..dd4b82d7510f68fb 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -62,7 +62,7 @@ static struct subsys_private *bus_to_subsys(const struct bus_type *bus)
> struct subsys_private *sp = NULL;
> struct kobject *kobj;
>
> - if (!bus)
> + if (!bus || !bus_kset)
> return NULL;
>
> spin_lock(&bus_kset->list_lock);

Thanks for this, I'll queue it up after my patches get sent to Linus.

greg k-h

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