usb 5-1: USB disconnect, device number 95
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BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
BUG: KASAN: use-after-free in refcount_inc_not_zero_checked+0x72/0x1e0 lib/refcount.c:123
Read of size 4 at addr ffff8881c707c820 by task kworker/0:2/101

CPU: 0 PID: 101 Comm: kworker/0:2 Not tainted 5.4.0-rc6-syzkaller #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+0xca/0x13e lib/dump_stack.c:113
 print_address_description.constprop.0+0x36/0x50 mm/kasan/report.c:374
 __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:506
 kasan_report+0xe/0x20 mm/kasan/common.c:634
 check_memory_region_inline mm/kasan/generic.c:185 [inline]
 check_memory_region+0x128/0x190 mm/kasan/generic.c:192
 atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
 refcount_inc_not_zero_checked+0x72/0x1e0 lib/refcount.c:123
 refcount_inc_checked+0x12/0x60 lib/refcount.c:156
 get_task_struct include/linux/sched/task.h:110 [inline]
 kthread_stop+0x6c/0x610 kernel/kthread.c:554
 hwrng_unregister+0x190/0x210 drivers/char/hw_random/core.c:538
 chaoskey_disconnect+0x1b2/0x200 drivers/usb/misc/chaoskey.c:232
 usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:423
 __device_release_driver drivers/base/dd.c:1134 [inline]
 device_release_driver_internal+0x42f/0x500 drivers/base/dd.c:1165
 bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:532
 device_del+0x420/0xb20 drivers/base/core.c:2376
 usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
 usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2200
 hub_port_connect drivers/usb/core/hub.c:5035 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5324 [inline]
 port_event drivers/usb/core/hub.c:5470 [inline]
 hub_event+0x16f2/0x3800 drivers/usb/core/hub.c:5552
 process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
 worker_thread+0x96/0xe20 kernel/workqueue.c:2415
 kthread+0x318/0x420 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 24104:
 save_stack+0x1b/0x80 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc mm/kasan/common.c:510 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:483
 slab_post_alloc_hook mm/slab.h:584 [inline]
 slab_alloc_node mm/slub.c:2779 [inline]
 slab_alloc mm/slub.c:2787 [inline]
 kmem_cache_alloc+0xd8/0x2e0 mm/slub.c:2792
 getname_flags fs/namei.c:138 [inline]
 getname_flags+0xd2/0x5b0 fs/namei.c:128
 do_sys_open+0x294/0x580 fs/open.c:1091
 do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 24104:
 save_stack+0x1b/0x80 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 kasan_set_free_info mm/kasan/common.c:332 [inline]
 __kasan_slab_free+0x130/0x180 mm/kasan/common.c:471
 slab_free_hook mm/slub.c:1424 [inline]
 slab_free_freelist_hook mm/slub.c:1475 [inline]
 slab_free mm/slub.c:3025 [inline]
 kmem_cache_free+0xb9/0x380 mm/slub.c:3041
 putname+0xe1/0x120 fs/namei.c:259
 do_sys_open+0x2e2/0x580 fs/open.c:1106
 do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881c707c400
 which belongs to the cache names_cache of size 4096
The buggy address is located 1056 bytes inside of
 4096-byte region [ffff8881c707c400, ffff8881c707d400)
The buggy address belongs to the page:
page:ffffea00071c1e00 refcount:1 mapcount:0 mapping:ffff8881da11c000 index:0x0 compound_mapcount: 0
flags: 0x200000000010200(slab|head)
raw: 0200000000010200 dead000000000100 dead000000000122 ffff8881da11c000
raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c707c700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881c707c780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881c707c800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8881c707c880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881c707c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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