Hello,
syzbot has tested the proposed patch but the reproducer still triggered crash:
KASAN: use-after-free Read in __input_unregister_device
wacom 0003:056A:0061.0002: Unknown device_type for 'HID 056a:0061'. Assuming pen.
input: Wacom PenStation2 Pen as /devices/platform/dummy_hcd.1/usb2/2-1/2-1:0.0/0003:056A:0061.0002/input/input8
wacom 0003:056A:0061.0002: hidraw1: USB HID v0.00 Device [HID 056a:0061] on usb-dummy_hcd.1-1/input0
usb 6-1: USB disconnect, device number 2
==================================================================
BUG: KASAN: use-after-free in __input_unregister_device+0x4a6/0x4c0 drivers/input/input.c:2089
Read of size 4 at addr ffff8881cc1380e8 by task kworker/0:1/12
CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.6.0-rc7-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+0xef/0x16e lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xd3/0x314 mm/kasan/report.c:374
__kasan_report.cold+0x37/0x77 mm/kasan/report.c:506
kasan_report+0xe/0x20 mm/kasan/common.c:641
__input_unregister_device+0x4a6/0x4c0 drivers/input/input.c:2089
release_nodes+0x499/0x910 drivers/base/devres.c:507
devres_release_group+0x160/0x210 drivers/base/devres.c:678
wacom_release_resources drivers/hid/wacom_sys.c:2238 [inline]
wacom_remove+0x244/0x3b0 drivers/hid/wacom_sys.c:2786
hid_device_remove+0xed/0x240 drivers/hid/hid-core.c:2296
__device_release_driver drivers/base/dd.c:1135 [inline]
device_release_driver_internal+0x231/0x500 drivers/base/dd.c:1168
bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:533
device_del+0x481/0xd30 drivers/base/core.c:2677
hid_remove_device drivers/hid/hid-core.c:2467 [inline]
hid_destroy_device+0xe1/0x150 drivers/hid/hid-core.c:2486
usbhid_disconnect+0x9f/0xe0 drivers/hid/usbhid/hid-core.c:1419
usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:436
__device_release_driver drivers/base/dd.c:1137 [inline]
device_release_driver_internal+0x42f/0x500 drivers/base/dd.c:1168
bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:533
device_del+0x481/0xd30 drivers/base/core.c:2677
usb_disable_device+0x23d/0x790 drivers/usb/core/message.c:1238
usb_disconnect+0x293/0x900 drivers/usb/core/hub.c:2211
hub_port_connect drivers/usb/core/hub.c:5046 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5335 [inline]
port_event drivers/usb/core/hub.c:5481 [inline]
hub_event+0x1a1d/0x4300 drivers/usb/core/hub.c:5563
process_one_work+0x94b/0x1620 kernel/workqueue.c:2266
worker_thread+0x96/0xe20 kernel/workqueue.c:2412
kthread+0x318/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Allocated by task 3265:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
__kasan_kmalloc mm/kasan/common.c:515 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:488
slab_post_alloc_hook mm/slab.h:584 [inline]
slab_alloc_node mm/slub.c:2786 [inline]
slab_alloc mm/slub.c:2794 [inline]
kmem_cache_alloc+0xd8/0x300 mm/slub.c:2799
getname_flags fs/namei.c:138 [inline]
getname_flags+0xd2/0x5b0 fs/namei.c:128
user_path_at_empty+0x2a/0x50 fs/namei.c:2746
user_path_at include/linux/namei.h:58 [inline]
do_faccessat+0x248/0x7a0 fs/open.c:398
do_syscall_64+0xb6/0x5a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 3265:
save_stack+0x1b/0x80 mm/kasan/common.c:72
set_track mm/kasan/common.c:80 [inline]
kasan_set_free_info mm/kasan/common.c:337 [inline]
__kasan_slab_free+0x117/0x160 mm/kasan/common.c:476
slab_free_hook mm/slub.c:1444 [inline]
slab_free_freelist_hook mm/slub.c:1477 [inline]
slab_free mm/slub.c:3034 [inline]
kmem_cache_free+0x9b/0x360 mm/slub.c:3050
putname+0xe1/0x120 fs/namei.c:259
filename_lookup+0x282/0x3e0 fs/namei.c:2475
user_path_at include/linux/namei.h:58 [inline]
do_faccessat+0x248/0x7a0 fs/open.c:398
do_syscall_64+0xb6/0x5a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
The buggy address belongs to the object at ffff8881cc138000
which belongs to the cache names_cache of size 4096
The buggy address is located 232 bytes inside of
4096-byte region [ffff8881cc138000, ffff8881cc139000)
The buggy address belongs to the page:
page:ffffea0007304e00 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:
ffff8881cc137f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881cc138000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881cc138080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881cc138100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881cc138180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Tested on:
commit: 0fa84af8 Merge tag 'usb-serial-5.7-rc1' of https://git.ker..
git tree: https://github.com/google/kasan.git
console output: https://syzkaller.appspot.com/x/log.txt?x=169d38d7e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=6b9c154b0c23aecf
dashboard link: https://syzkaller.appspot.com/bug?extid=7bf5a7b0f0a1f9446f4c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
patch: https://syzkaller.appspot.com/x/patch.diff?x=17a95273e00000
