[PATCH] pmdomain: arm: Fix NULL dereference on scmi_perf_domain removal

[Cristian Marussi <cristian.marussi@arm.com>]

On unloading of the scmi_perf_domain module got the below splat, when in
the DT provided to the system under test the '#power-domain-cells' property
was missing.
Indeed, this particular setup causes the probe to bail out early without
giving any error, so that, then, the removal code is run on unload, but
without all the expected initialized structures in place.

Add a check and bail out early on remove too.

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
Mem abort info:
   ESR = 0x0000000096000004
   EC = 0x25: DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
   FSC = 0x04: level 0 translation fault
 Data abort info:
   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
 user pgtable: 4k pages, 48-bit VAs, pgdp=00000001076e5000
 [0000000000000008] pgd=0000000000000000, p4d=0000000000000000
 Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
 Modules linked in: scmi_perf_domain(-) scmi_module scmi_core
 CPU: 0 PID: 231 Comm: rmmod Not tainted 6.7.0-00084-gb4b1f27d3b83-dirty #15
 Hardware name: linux,dummy-virt (DT)
 pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
 pc : scmi_perf_domain_remove+0x28/0x70 [scmi_perf_domain]
 lr : scmi_perf_domain_remove+0x28/0x70 [scmi_perf_domain]
 sp : ffff80008393bc10
 x29: ffff80008393bc10 x28: ffff0000875a8000 x27: 0000000000000000
 x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
 x23: ffff00008030c090 x22: ffff00008032d490 x21: ffff80007b287050
 x20: 0000000000000000 x19: ffff00008032d410 x18: 0000000000000000
 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
 x14: 8ba0696d05013a2f x13: 0000000000000000 x12: 0000000000000002
 x11: 0101010101010101 x10: ffff00008510cff8 x9 : ffff800080a6797c
 x8 : 0101010101010101 x7 : 7f7f7f7f7f7f7f7f x6 : fefefeff6364626d
 x5 : 8080808000000000 x4 : 0000000000000020 x3 : 00000000553a3dc1
 x2 : ffff0000875a8000 x1 : ffff0000875a8000 x0 : ffff800082ffa048
 Call trace:
  scmi_perf_domain_remove+0x28/0x70 [scmi_perf_domain]
  scmi_dev_remove+0x28/0x40 [scmi_core]
  device_remove+0x54/0x90
  device_release_driver_internal+0x1dc/0x240
  driver_detach+0x58/0xa8
  bus_remove_driver+0x78/0x108
  driver_unregister+0x38/0x70
  scmi_driver_unregister+0x28/0x180 [scmi_core]
  scmi_perf_domain_driver_exit+0x18/0xb78 [scmi_perf_domain]
  __arm64_sys_delete_module+0x1a8/0x2c0
  invoke_syscall+0x50/0x128
  el0_svc_common.constprop.0+0x48/0xf0
  do_el0_svc+0x24/0x38
  el0_svc+0x34/0xb8
  el0t_64_sync_handler+0x100/0x130
  el0t_64_sync+0x190/0x198
 Code: a90153f3 f9403c14 f9414800 955f8a05 (b9400a80)
 ---[ end trace 0000000000000000 ]---

Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Fixes: 2af23ceb8624 ("pmdomain: arm: Add the SCMI performance domain")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
I suppose the probe does NOT bail out with an error because this DT config has
to be supported, right ?
---
 drivers/pmdomain/arm/scmi_perf_domain.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pmdomain/arm/scmi_perf_domain.c b/drivers/pmdomain/arm/scmi_perf_domain.c
index 709bbc448fad..d7ef46ccd9b8 100644
--- a/drivers/pmdomain/arm/scmi_perf_domain.c
+++ b/drivers/pmdomain/arm/scmi_perf_domain.c
@@ -159,6 +159,9 @@ static void scmi_perf_domain_remove(struct scmi_device *sdev)
 	struct genpd_onecell_data *scmi_pd_data = dev_get_drvdata(dev);
 	int i;
 
+	if (!scmi_pd_data)
+		return;
+
 	of_genpd_del_provider(dev->of_node);
 
 	for (i = 0; i < scmi_pd_data->num_domains; i++)
-- 
2.43.0