WARNING: proc registration bug in snd_info_card_register

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    9a33b369 usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan/tree/usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=1738acd3200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=23e37f59d94ddd15
dashboard link: https://syzkaller.appspot.com/bug?extid=2e782bf6a60d0fcb932d
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=140ef0f3200000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=102c7c2d200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2e782bf6a60d0fcb932d@xxxxxxxxxxxxxxxxxxxxxxxxx

usb 1-1: send failed (error -71)
usb 6-1: send failed (error -71)
usb 5-1: USB disconnect, device number 3
------------[ cut here ]------------
proc_dir_entry 'asound/PODStudioUX2' already registered
WARNING: CPU: 1 PID: 534 at fs/proc/generic.c:359 proc_register+0x3d9/0x550  
fs/proc/generic.c:359
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 534 Comm: kworker/1:2 Not tainted 5.1.0-rc4-319354-g9a33b36 #3
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+0xe8/0x16e lib/dump_stack.c:113
 panic+0x29d/0x5f2 kernel/panic.c:214
 __warn.cold+0x20/0x48 kernel/panic.c:571
 report_bug+0x262/0x2a0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x130/0x1f0 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x40 arch/x86/kernel/traps.c:291
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:proc_register+0x3d9/0x550 fs/proc/generic.c:359
Code: ff df 48 89 f9 48 c1 e9 03 80 3c 01 00 0f 85 61 01 00 00 48 8b 04 24  
48 c7 c7 e0 a0 79 8e 48 8b b0 d0 00 00 00 e8 a7 9e 71 ff <0f> 0b 48 c7 c7  
a0 90 91 91 e8 b9 10 34 0c 48 8b 4c 24 28 48 b8 00
RSP: 0018:ffff88809fb9f000 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff88809d2df840 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815b1e42 RDI: ffffed1013f73df2
RBP: ffff888096382a00 R08: ffff88809f9cc980 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff8880a594cd38 R15: 000000000000000c
 proc_symlink+0x147/0x1c0 fs/proc/generic.c:451
 snd_info_card_register+0x14b/0x1e0 sound/core/info.c:558
 snd_card_register sound/core/init.c:772 [inline]
 snd_card_register+0x432/0x5f0 sound/core/init.c:736
 toneport_init sound/usb/line6/toneport.c:457 [inline]
 toneport_init+0x256/0x63c sound/usb/line6/toneport.c:412
 line6_probe+0xb01/0x1150 sound/usb/line6/driver.c:784
 usb_probe_interface+0x31d/0x820 drivers/usb/core/driver.c:361
 really_probe+0x2da/0xb10 drivers/base/dd.c:509
 driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
 __device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
 bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
 __device_attach+0x223/0x3a0 drivers/base/dd.c:844
 bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
 device_add+0xad2/0x16e0 drivers/base/core.c:2106
 usb_set_configuration+0xdf7/0x1740 drivers/usb/core/message.c:2021
 generic_probe+0xa2/0xda drivers/usb/core/generic.c:210
 usb_probe_device+0xc0/0x150 drivers/usb/core/driver.c:266
 really_probe+0x2da/0xb10 drivers/base/dd.c:509
 driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
 __device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
 bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
 __device_attach+0x223/0x3a0 drivers/base/dd.c:844
 bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
 device_add+0xad2/0x16e0 drivers/base/core.c:2106
 usb_new_device.cold+0x537/0xccf drivers/usb/core/hub.c:2534
 hub_port_connect drivers/usb/core/hub.c:5089 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
 port_event drivers/usb/core/hub.c:5350 [inline]
 hub_event+0x138e/0x3b00 drivers/usb/core/hub.c:5432
 process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
 process_scheduled_works kernel/workqueue.c:2331 [inline]
 worker_thread+0x7b0/0xe20 kernel/workqueue.c:2417
 kthread+0x313/0x420 kernel/kthread.c:253
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


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