[PATCH v2] driver core: platform: don't oops in platform_shutdown() on unbound devices

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

Platform code stopped checking if the device is bound to the actual
platform driver, thus calling non-existing drv->shutdown(). Verify that
_dev->driver is not NULL before calling shutdown callback.

[   57.832972] platform 3d6a000.gmu: shutdown
[   57.837778] Unable to handle kernel paging request at virtual address ffffffffffffffe8
[   57.846391] Mem abort info:
[   57.849704]   ESR = 0x96000004
[   57.853286]   EC = 0x25: DABT (current EL), IL = 32 bits
[   57.859177]   SET = 0, FnV = 0
[   57.862751]   EA = 0, S1PTW = 0
[   57.866415] Data abort info:
[   57.869801]   ISV = 0, ISS = 0x00000004
[   57.874171]   CM = 0, WnR = 0
[   57.877634] swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000000a1646000
[   57.884937] [ffffffffffffffe8] pgd=0000000000000000, p4d=0000000000000000
[   57.892323] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[   57.898471] Modules linked in:
[   57.902022] CPU: 7 PID: 387 Comm: reboot Tainted: G        W  5.10.0-rc7-next-20201211-13328-gb9e15b9c1940-dirty #1270
[   57.914043] Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
[   57.921340] pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--)
[   57.927930] pc : platform_shutdown+0x8/0x34
[   57.932661] lr : device_shutdown+0x158/0x32c
[   57.937483] sp : ffff800010773c70
[   57.941319] x29: ffff800010773c70 x28: ffff14f80c41c600
[   57.947208] x27: 0000000000000000 x26: ffff14f80129c490
[   57.953100] x25: ffffaa6264ece398 x24: 0000000000000008
[   57.958990] x23: ffffaa62655be030 x22: ffffaa6265671600
[   57.964875] x21: ffff14f80122b010 x20: ffff14f80129c410
[   57.970765] x19: ffff14f80129c418 x18: 0000000000000030
[   57.976665] x17: 0000000000000000 x16: 0000000000000001
[   57.982590] x15: 0000000000000004 x14: 000000000000019f
[   57.988478] x13: 0000000000000000 x12: 0000000000000000
[   57.994394] x11: 0000000000000000 x10: 00000000000009b0
[   58.000297] x9 : ffff800010773920 x8 : ffff14f80c41d010
[   58.006205] x7 : ffff14f976ff59c0 x6 : 0000000000000192
[   58.012112] x5 : 0000000000000000 x4 : ffff14f976feb920
[   58.018023] x3 : ffff14f976ff2878 x2 : 0000000000000000
[   58.023940] x1 : 0000000000000000 x0 : ffff14f80129c410
[   58.029871] Call trace:
[   58.032849]  platform_shutdown+0x8/0x34
[   58.037256]  kernel_restart+0x40/0xa0
[   58.041485]  __do_sys_reboot+0x228/0x250
[   58.045975]  __arm64_sys_reboot+0x28/0x34
[   58.050571]  el0_svc_common+0x7c/0x1a0
[   58.054886]  do_el0_svc+0x28/0x94
[   58.058754]  el0_svc+0x14/0x20
[   58.062371]  el0_sync_handler+0x1a4/0x1b0
[   58.066951]  el0_sync+0x174/0x180
[   58.070822] Code: d503201f d503201f d503245f f9403401 (f85e8021)
[   58.077532] ---[ end trace 26b521c0dca4c8d0 ]---

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Fixes: 9c30921fe799 ("driver core: platform: use bus_type functions")
---
 drivers/base/platform.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 0358dc3ea3ad..e9477e0bbca5 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -1351,9 +1351,13 @@ static int platform_remove(struct device *_dev)
 
 static void platform_shutdown(struct device *_dev)
 {
-	struct platform_driver *drv = to_platform_driver(_dev->driver);
 	struct platform_device *dev = to_platform_device(_dev);
+	struct platform_driver *drv;
+
+	if (!_dev->driver)
+		return;
 
+	drv = to_platform_driver(_dev->driver);
 	if (drv->shutdown)
 		drv->shutdown(dev);
 }
-- 
2.29.2