um: ubd: Do not use drvdata in release

The drvdata is not available in release. Let's just use container_of()
to get the ubd instance. Otherwise, removing a ubd device will result
in a crash:

RIP: 0033:blk_mq_free_tag_set+0x1f/0xba
RSP: 00000000e2083bf0  EFLAGS: 00010246
RAX: 000000006021463a RBX: 0000000000000348 RCX: 0000000062604d00
RDX: 0000000004208060 RSI: 00000000605241a0 RDI: 0000000000000348
RBP: 00000000e2083c10 R08: 0000000062414010 R09: 00000000601603f7
R10: 000000000000133a R11: 000000006038c4bd R12: 0000000000000000
R13: 0000000060213a5c R14: 0000000062405d20 R15: 00000000604f7aa0
Kernel panic - not syncing: Segfault with no mm
CPU: 0 PID: 17 Comm: kworker/0:1 Not tainted 6.8.0-rc3-00107-gba3f67c11638 #1
Workqueue: events mc_work_proc
Stack:
 00000000 604f7ef0 62c5d000 62405d20
 e2083c30 6002c776 6002c755 600e47ff
 e2083c60 6025ffe3 04208060 603d36e0
Call Trace:
 [<6002c776>] ubd_device_release+0x21/0x55
 [<6002c755>] ? ubd_device_release+0x0/0x55
 [<600e47ff>] ? kfree+0x0/0x100
 [<6025ffe3>] device_release+0x70/0xba
 [<60381d6a>] kobject_put+0xb5/0xe2
 [<6026027b>] put_device+0x19/0x1c
 [<6026a036>] platform_device_put+0x26/0x29
 [<6026ac5a>] platform_device_unregister+0x2c/0x2e
 [<6002c52e>] ubd_remove+0xb8/0xd6
 [<6002bb74>] ? mconsole_reply+0x0/0x50
 [<6002b926>] mconsole_remove+0x160/0x1cc
 [<6002bbbc>] ? mconsole_reply+0x48/0x50
 [<6003379c>] ? um_set_signals+0x3b/0x43
 [<60061c55>] ? update_min_vruntime+0x14/0x70
 [<6006251f>] ? dequeue_task_fair+0x164/0x235
 [<600620aa>] ? update_cfs_group+0x0/0x40
 [<603a0e77>] ? __schedule+0x0/0x3ed
 [<60033761>] ? um_set_signals+0x0/0x43
 [<6002af6a>] mc_work_proc+0x77/0x91
 [<600520b4>] process_scheduled_works+0x1af/0x2c3
 [<6004ede3>] ? assign_work+0x0/0x58
 [<600527a1>] worker_thread+0x2f7/0x37a
 [<6004ee3b>] ? set_pf_worker+0x0/0x64
 [<6005765d>] ? arch_local_irq_save+0x0/0x2d
 [<60058e07>] ? kthread_exit+0x0/0x3a
 [<600524aa>] ? worker_thread+0x0/0x37a
 [<60058f9f>] kthread+0x130/0x135
 [<6002068e>] new_thread_handler+0x85/0xb6

Cc: [email protected]
Signed-off-by: Tiwei Bie <[email protected]>
Acked-By: Anton Ivanov <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

arch/um/drivers/ubd_kern.c

@@ -779,7 +779,7 @@ static int ubd_open_dev(struct ubd *ubd_dev)
 
 static void ubd_device_release(struct device *dev)
 {
-	struct ubd *ubd_dev = dev_get_drvdata(dev);
+	struct ubd *ubd_dev = container_of(dev, struct ubd, pdev.dev);
 
 	blk_mq_free_tag_set(&ubd_dev->tag_set);
 	*ubd_dev = ((struct ubd) DEFAULT_UBD);