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Subject[PATCH] driver core: bus: Handle early calls to bus_to_subsys()
Date
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);
--
2.34.1
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