kernel BUG in attach_store

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    0e2c50f4 Add linux-next specific files for 20210204
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1294915f500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b5009c5bf1512a87
dashboard link: https://syzkaller.appspot.com/bug?extid=a30e620779ec2718f731
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1047b68cd00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=150f3f6f500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a30e620779ec2718f731@xxxxxxxxxxxxxxxxxxxxxxxxx

------------[ cut here ]------------
kernel BUG at drivers/usb/usbip/vhci_sysfs.c:396!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 9885 Comm: syz-executor837 Not tainted 5.11.0-rc6-next-20210204-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:attach_store.cold+0x376/0x396 drivers/usb/usbip/vhci_sysfs.c:396
Code: e8 b9 3d d0 f8 48 8b 5d 70 48 c7 c7 00 f0 ff ff 48 89 de e8 66 97 8c f8 48 81 fb 00 f0 ff ff 0f 87 56 ff ff ff e8 64 8f 8c f8 <0f> 0b e8 5d 8f 8c f8 8b b4 24 90 00 00 00 48 89 ef e8 fe 31 b4 fc
RSP: 0018:ffffc9000ad47b58 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff8880206c1c00 RCX: 0000000000000000
RDX: ffff888020909c00 RSI: ffffffff88e65b5c RDI: 0000000000000003
RBP: ffff8881445785d0 R08: fffffffffffff000 R09: ffff88802282d8a7
R10: ffffffff88e65b4a R11: 000000000000003f R12: fffffffffffffffc
R13: ffff888144578640 R14: ffff8881445785e8 R15: ffff888031a38fc0
FS:  00007f294068c700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004df500 CR3: 0000000029449000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 dev_attr_store+0x50/0x80 drivers/base/core.c:1936
 sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139
 kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:1977 [inline]
 new_sync_write+0x426/0x650 fs/read_write.c:519
 vfs_write+0x791/0xa30 fs/read_write.c:606
 ksys_write+0x12d/0x250 fs/read_write.c:659
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x40b5ff
Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 99 fd ff ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 cc fd ff ff 48
RSP: 002b:00007f294068bd60 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 000000000040b5ff
RDX: 0000000000000008 RSI: 00007f294068bdb0 RDI: 0000000000000005
RBP: 0000000000000005 R08: 0000000000000000 R09: 00007f294068bd00
R10: 0000000000000000 R11: 0000000000000293 R12: 00007f294068bdb0
R13: 0000000000000000 R14: 00007f294068c400 R15: 0000000000022000
Modules linked in:

---[ end trace 375e0f0107ff6180 ]---
RIP: 0010:attach_store.cold+0x376/0x396 drivers/usb/usbip/vhci_sysfs.c:396
Code: e8 b9 3d d0 f8 48 8b 5d 70 48 c7 c7 00 f0 ff ff 48 89 de e8 66 97 8c f8 48 81 fb 00 f0 ff ff 0f 87 56 ff ff ff e8 64 8f 8c f8 <0f> 0b e8 5d 8f 8c f8 8b b4 24 90 00 00 00 48 89 ef e8 fe 31 b4 fc
RSP: 0018:ffffc9000ad47b58 EFLAGS: 00010293

RAX: 0000000000000000 RBX: ffff8880206c1c00 RCX: 0000000000000000
RDX: ffff888020909c00 RSI: ffffffff88e65b5c RDI: 0000000000000003
RBP: ffff8881445785d0 R08: fffffffffffff000 R09: ffff88802282d8a7
R10: ffffffff88e65b4a R11: 000000000000003f R12: fffffffffffffffc
R13: ffff888144578640 R14: ffff8881445785e8 R15: ffff888031a38fc0
FS:  00007f294068c700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004d1974 CR3: 0000000029449000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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