general protection fault in line6_midibuf_write

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    3ed8e1c2 usb: typec: tcpm: Migrate workqueue to RT priorit..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=137be056900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ccafc70ac3d5f49c
dashboard link: https://syzkaller.appspot.com/bug?extid=b333bd4e812c1d42827a
compiler:       gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b333bd4e812c1d42827a at syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000019: 0000 [#1] SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000c8-0x00000000000000cf]
CPU: 1 PID: 21 Comm: kworker/1:1 Not tainted 5.9.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usb_hub_wq hub_event
RIP: 0010:midibuf_is_full sound/usb/line6/midibuf.c:44 [inline]
RIP: 0010:line6_midibuf_write+0x30/0x3f0 sound/usb/line6/midibuf.c:91
Code: 49 89 f5 41 54 55 89 d5 53 48 89 fb 4c 8d 7b 18 48 83 ec 28 e8 11 68 5f fc 4c 89 fa 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 0a 03 00 00 44 8b 63 18 31 ff
RSP: 0018:ffff8881db3099d8 EFLAGS: 00010002
RAX: dffffc0000000000 RBX: 00000000000000b0 RCX: ffffc900006a8000
RDX: 0000000000000019 RSI: ffffffff84e098af RDI: 00000000000000b0
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8734d643
R10: 0000000000000000 R11: 000000000004e017 R12: 00000000000000b0
R13: ffff8881d40aec80 R14: ffff8881d4464984 R15: 00000000000000c8
FS:  0000000000000000(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005629deed5130 CR3: 00000001d2254000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 line6_data_received+0x281/0x520 sound/usb/line6/driver.c:296
 __usb_hcd_giveback_urb+0x32d/0x560 drivers/usb/core/hcd.c:1650
 usb_hcd_giveback_urb+0x367/0x410 drivers/usb/core/hcd.c:1716
 dummy_timer+0x11f2/0x3240 drivers/usb/gadget/udc/dummy_hcd.c:1967
 call_timer_fn+0x1ac/0x6e0 kernel/time/timer.c:1413
 expire_timers kernel/time/timer.c:1458 [inline]
 __run_timers.part.0+0x67c/0xa60 kernel/time/timer.c:1755
 __run_timers kernel/time/timer.c:1736 [inline]
 run_timer_softirq+0x80/0x120 kernel/time/timer.c:1768
 __do_softirq+0x1af/0x91c kernel/softirq.c:298
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 do_softirq_own_stack+0x73/0x90 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:393 [inline]
 __irq_exit_rcu kernel/softirq.c:423 [inline]
 irq_exit_rcu+0x107/0x1a0 kernel/softirq.c:435
 sysvec_apic_timer_interrupt+0x43/0x90 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/irqflags.h:85 [inline]
RIP: 0010:console_unlock+0xa99/0xcd0 kernel/printk/printk.c:2509
Code: 00 89 ee 48 c7 c7 a0 0a 35 87 e8 12 b9 03 00 65 ff 0d 3b 48 d8 7e e9 87 f9 ff ff e8 f1 59 16 00 e8 dc f2 1b 00 ff 74 24 30 9d <e9> 20 fe ff ff e8 dd 59 16 00 48 8d 7d 08 48 89 f8 48 c1 e8 03 42
RSP: 0018:ffff8881da34f5e0 EFLAGS: 00000212
RAX: 00000000000d56ed RBX: 0000000000000200 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8129a6d4
RBP: 0000000000000000 R08: 0000000000000001 R09: ffffffff895c65e7
R10: fffffbfff12b8cbc R11: 0000000000003254 R12: ffffffff82b3d6f0
R13: ffffffff876fa450 R14: 0000000000000054 R15: dffffc0000000000
 vprintk_emit+0x1b2/0x460 kernel/printk/printk.c:2029
 dev_vprintk_emit+0x3eb/0x436 drivers/base/core.c:4133
 dev_printk_emit+0xba/0xf1 drivers/base/core.c:4144
 __dev_printk+0xcf/0xf5 drivers/base/core.c:4156
 _dev_info+0xd7/0x109 drivers/base/core.c:4202
 hub_port_init.cold+0x264/0x32f drivers/usb/core/hub.c:4628
 hub_port_connect drivers/usb/core/hub.c:5140 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5348 [inline]
 port_event drivers/usb/core/hub.c:5494 [inline]
 hub_event+0x2191/0x4390 drivers/usb/core/hub.c:5576
 process_one_work+0x94c/0x15f0 kernel/workqueue.c:2269
 process_scheduled_works kernel/workqueue.c:2331 [inline]
 worker_thread+0x82b/0x1120 kernel/workqueue.c:2417
 kthread+0x392/0x470 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Modules linked in:
---[ end trace 3dff073ad8b565c9 ]---
RIP: 0010:midibuf_is_full sound/usb/line6/midibuf.c:44 [inline]
RIP: 0010:line6_midibuf_write+0x30/0x3f0 sound/usb/line6/midibuf.c:91
Code: 49 89 f5 41 54 55 89 d5 53 48 89 fb 4c 8d 7b 18 48 83 ec 28 e8 11 68 5f fc 4c 89 fa 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 0a 03 00 00 44 8b 63 18 31 ff
RSP: 0018:ffff8881db3099d8 EFLAGS: 00010002
RAX: dffffc0000000000 RBX: 00000000000000b0 RCX: ffffc900006a8000
RDX: 0000000000000019 RSI: ffffffff84e098af RDI: 00000000000000b0
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8734d643
R10: 0000000000000000 R11: 000000000004e017 R12: 00000000000000b0
R13: ffff8881d40aec80 R14: ffff8881d4464984 R15: 00000000000000c8
FS:  0000000000000000(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005629deed5130 CR3: 00000001d2254000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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