divide error in usbnet_update_max_qlen

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    f0df5c1b 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=117659fa600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=6102c120be558c885f04
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12107ba9600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=146014e6600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6102c120be558c885f04@xxxxxxxxxxxxxxxxxxxxxxxxx

usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
cdc_ncm 1-1:1.0: MAC-Address: 42:42:42:42:42:42
cdc_ncm 1-1:1.0: dwNtbInMaxSize=0 is too small. Using 2048
cdc_ncm 1-1:1.0: setting rx_max = 2048
divide error: 0000 [#1] SMP KASAN
CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
RIP: 0010:usbnet_update_max_qlen drivers/net/usb/usbnet.c:344 [inline]
RIP: 0010:usbnet_update_max_qlen+0x231/0x370 drivers/net/usb/usbnet.c:338
Code: 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 46 01  
00 00 48 8d bb f4 00 00 00 31 d2 b8 c8 63 01 00 48 89 f9 <48> f7 b3 a8 01  
00 00 48 ba 00 00 00 00 00 fc ff df 48 c1 e9 03 0f
RSP: 0018:ffff8881da20f010 EFLAGS: 00010246
RAX: 00000000000163c8 RBX: ffff8881d5ad8ac0 RCX: ffff8881d5ad8bb4
RDX: 0000000000000000 RSI: ffffffff8344ecde RDI: ffff8881d5ad8bb4
RBP: 0000000000000003 R08: ffff8881da1f9800 R09: ffffed103ab5b00a
R10: ffffed103ab5b009 R11: ffff8881d5ad804f R12: 0000000000000000
R13: ffff8881d5ad8c38 R14: ffff8881d5ad8ac0 R15: ffff8881d2820c80
FS:  0000000000000000(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f26d0180000 CR3: 00000001d38dd000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 cdc_ncm_update_rxtx_max+0x8e9/0xef0 drivers/net/usb/cdc_ncm.c:440
 cdc_ncm_setup drivers/net/usb/cdc_ncm.c:667 [inline]
 cdc_ncm_bind_common+0x1005/0x2570 drivers/net/usb/cdc_ncm.c:924
 cdc_ncm_bind+0x7c/0x1c0 drivers/net/usb/cdc_ncm.c:1038
 usbnet_probe+0xb43/0x23cf drivers/net/usb/usbnet.c:1722
 usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
 really_probe+0x281/0x6d0 drivers/base/dd.c:548
 driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
 __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
 bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:454
 __device_attach+0x217/0x360 drivers/base/dd.c:894
 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
 device_add+0xae6/0x16f0 drivers/base/core.c:2165
 usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
 generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
 usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
 really_probe+0x281/0x6d0 drivers/base/dd.c:548
 driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
 __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
 bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:454
 __device_attach+0x217/0x360 drivers/base/dd.c:894
 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
 device_add+0xae6/0x16f0 drivers/base/core.c:2165
 usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2536
 hub_port_connect drivers/usb/core/hub.c:5098 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
 port_event drivers/usb/core/hub.c:5359 [inline]
 hub_event+0x1b5c/0x3640 drivers/usb/core/hub.c:5441


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches