Re: divide error in cdc_ncm_update_rxtx_max

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer still triggered  
crash:
divide error in usbnet_update_max_qlen

cdc_ncm 5-1:1.0: setting tx_max = 16384
divide error: 0000 [#1] SMP KASAN
CPU: 1 PID: 1737 Comm: kworker/1:2 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:ffff8881c05c7010 EFLAGS: 00010246
RAX: 00000000000163c8 RBX: ffff8881c7334ec0 RCX: ffff8881c7334fb4
RDX: 0000000000000000 RSI: ffffffff8344ecde RDI: ffff8881c7334fb4
RBP: 0000000000000003 R08: ffff8881d4a9b000 R09: ffffed1038e6688a
R10: ffffed1038e66889 R11: ffff8881c733444f R12: 0000000000004000
R13: ffff8881c7334ec0 R14: 0000000000000000 R15: ffff8881d62e77ac
FS:  0000000000000000(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5a513e8000 CR3: 00000001d6436000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 cdc_ncm_update_rxtx_max+0xa61/0xf30 drivers/net/usb/cdc_ncm.c:437
 cdc_ncm_setup drivers/net/usb/cdc_ncm.c:664 [inline]
 cdc_ncm_bind_common+0x1005/0x2570 drivers/net/usb/cdc_ncm.c:921
 cdc_ncm_bind+0x7c/0x1c0 drivers/net/usb/cdc_ncm.c:1035
 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
 process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
 worker_thread+0x96/0xe20 kernel/workqueue.c:2415
 kthread+0x318/0x420 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace 472dbe98145a6d5e ]---
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:ffff8881c05c7010 EFLAGS: 00010246
RAX: 00000000000163c8 RBX: ffff8881c7334ec0 RCX: ffff8881c7334fb4
RDX: 0000000000000000 RSI: ffffffff8344ecde RDI: ffff8881c7334fb4
RBP: 0000000000000003 R08: ffff8881d4a9b000 R09: ffffed1038e6688a
R10: ffffed1038e66889 R11: ffff8881c733444f R12: 0000000000004000
R13: ffff8881c7334ec0 R14: 0000000000000000 R15: ffff8881d62e77ac
FS:  0000000000000000(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5a513e8000 CR3: 00000001d6436000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


Tested on:

commit:         f0df5c1b usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git
console output: https://syzkaller.appspot.com/x/log.txt?x=173ea979600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=ce366e2b8296e25d84f5
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1538611d600000