KMSAN: uninit-value in iowarrior_disconnect

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    014077b5 DO-NOT-SUBMIT: usb-fuzzer: main usb gadget fuzzer..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=108eae5e600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f03c659d0830ab8d
dashboard link: https://syzkaller.appspot.com/bug?extid=0761012cebf7bdb38137
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15161d99600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13632e3a600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0761012cebf7bdb38137@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KMSAN: uninit-value in iowarrior_disconnect+0x27a/0x3e0  
drivers/usb/misc/iowarrior.c:884
CPU: 0 PID: 11102 Comm: kworker/0:5 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x191/0x1f0 lib/dump_stack.c:113
 kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109
 __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294
 iowarrior_disconnect+0x27a/0x3e0 drivers/usb/misc/iowarrior.c:884
 usb_unbind_interface+0x3a2/0xdd0 drivers/usb/core/driver.c:423
 __device_release_driver drivers/base/dd.c:1120 [inline]
 device_release_driver_internal+0x911/0xd20 drivers/base/dd.c:1151
 device_release_driver+0x4b/0x60 drivers/base/dd.c:1174
 bus_remove_device+0x4bf/0x670 drivers/base/bus.c:556
 device_del+0xcd5/0x1d10 drivers/base/core.c:2339
 usb_disable_device+0x567/0x1150 drivers/usb/core/message.c:1241
 usb_disconnect+0x51e/0xd60 drivers/usb/core/hub.c:2199
 hub_port_connect drivers/usb/core/hub.c:4949 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
 port_event drivers/usb/core/hub.c:5359 [inline]
 hub_event+0x3fd0/0x72f0 drivers/usb/core/hub.c:5441
 process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
 worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
 kthread+0x4b5/0x4f0 kernel/kthread.c:256
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:189 [inline]
 kmsan_internal_poison_shadow+0x58/0xb0 mm/kmsan/kmsan.c:148
 kmsan_slab_free+0x8d/0x100 mm/kmsan/kmsan_hooks.c:195
 slab_free_freelist_hook mm/slub.c:1472 [inline]
 slab_free mm/slub.c:3038 [inline]
 kfree+0x4c1/0x2db0 mm/slub.c:3980
 iowarrior_delete drivers/usb/misc/iowarrior.c:246 [inline]
 iowarrior_release+0x334/0x3a0 drivers/usb/misc/iowarrior.c:670
 __fput+0x4c9/0xba0 fs/file_table.c:280
 ____fput+0x37/0x40 fs/file_table.c:313
 task_work_run+0x22e/0x2a0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:163 [inline]
 prepare_exit_to_usermode+0x39d/0x4d0 arch/x86/entry/common.c:194
 syscall_return_slowpath+0x90/0x610 arch/x86/entry/common.c:274
 do_syscall_64+0xe2/0xf0 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
==================================================================


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