divide error in usbtmc_generic_read

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    d0847550 usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=16295d4a600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dbc9c80cc095da19
dashboard link: https://syzkaller.appspot.com/bug?extid=55b0304b360654a7537b
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1288a31c600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15282e86600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+55b0304b360654a7537b@xxxxxxxxxxxxxxxxxxxxxxxxx

divide error: 0000 [#1] SMP KASAN
CPU: 1 PID: 1761 Comm: syz-executor063 Not tainted 5.3.0-rc4+ #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:usbtmc_generic_read+0x135/0x1190 drivers/usb/class/usbtmc.c:816
Code: 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 01 38 d0 7c 08 84 d2  
0f 85 50 08 00 00 41 0f b7 6e 34 31 d2 31 ff 8b 44 24 28 <f7> f5 89 d6 41  
89 d4 e8 2f 54 c9 fd 44 8b 6c 24 28 45 85 e4 44 89
RSP: 0018:ffff8881d2b77a58 EFLAGS: 00010246
RAX: 0000000000000002 RBX: 000000004f894bad RCX: ffffffff837487cd
RDX: 0000000000000000 RSI: ffffffff837487da RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff8881d20a0000 R09: ffffed103a56ef90
R10: ffffed103a56ef8f R11: 0000000000000003 R12: ffff8881d08e7180
R13: 0000000020000000 R14: ffff8881d0404c80 R15: ffff8881d08e7180
FS:  0000555555b74880(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006cc090 CR3: 00000001d615e000 CR4: 00000000001406e0
Call Trace:
 usbtmc_ioctl_generic_read drivers/usb/class/usbtmc.c:1029 [inline]
 usbtmc_ioctl+0x27d/0x2ab0 drivers/usb/class/usbtmc.c:2089
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xd2d/0x1330 fs/ioctl.c:696
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:718
 do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4419a9
Code: e8 8c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 cb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffd0abd6738 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004419a9
RDX: 0000000020000000 RSI: 00000000c0145b0e RDI: 0000000000000004
RBP: 000000000000a984 R08: 000000000000000f R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402700
R13: 0000000000402790 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace a91d281a4d83213c ]---
RIP: 0010:usbtmc_generic_read+0x135/0x1190 drivers/usb/class/usbtmc.c:816
Code: 48 c1 ea 03 0f b6 14 02 48 89 f8 83 e0 07 83 c0 01 38 d0 7c 08 84 d2  
0f 85 50 08 00 00 41 0f b7 6e 34 31 d2 31 ff 8b 44 24 28 <f7> f5 89 d6 41  
89 d4 e8 2f 54 c9 fd 44 8b 6c 24 28 45 85 e4 44 89
RSP: 0018:ffff8881d2b77a58 EFLAGS: 00010246
RAX: 0000000000000002 RBX: 000000004f894bad RCX: ffffffff837487cd
RDX: 0000000000000000 RSI: ffffffff837487da RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff8881d20a0000 R09: ffffed103a56ef90
R10: ffffed103a56ef8f R11: 0000000000000003 R12: ffff8881d08e7180
R13: 0000000020000000 R14: ffff8881d0404c80 R15: ffff8881d08e7180
FS:  0000555555b74880(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006cc090 CR3: 00000001d615e000 CR4: 00000000001406e0


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