Re: divide error in dummy_timer

[syzbot]

Hello,

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

divide error: 0000 [#1] SMP KASAN
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:transfer drivers/usb/gadget/udc/dummy_hcd.c:1426 [inline]
RIP: 0010:dummy_timer+0xad5/0x2fa2 drivers/usb/gadget/udc/dummy_hcd.c:1950
Code: 0f 84 f5 fd ff ff e8 2a 54 ab fd 89 de 44 89 e7 e8 10 55 ab fd 41 39  
dc 0f 82 b0 08 00 00 e8 12 54 ab fd 44 89 e0 31 d2 31 ff <f7> f3 89 d6 89  
94 24 c0 00 00 00 e8 6b 55 ab fd 8b 94 24 c0 00 00
RSP: 0018:ffff8881db309b20 EFLAGS: 00010046
RAX: 0000000000000040 RBX: 0000000000000000 RCX: ffffffff8392c490
RDX: 0000000000000000 RSI: ffffffff8392c49e RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff8881da213000 R09: ffffed103b661353
R10: ffffed103b661352 R11: 0000000000000003 R12: 0000000000000040
R13: ffff8881d4712a00 R14: dffffc0000000000 R15: ffff8881d20a2200
FS:  0000000000000000(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb31aad7000 CR3: 00000001d4b0e000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 call_timer_fn+0x179/0x650 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0x5e3/0x1490 kernel/time/timer.c:1786
 __do_softirq+0x221/0x912 kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x178/0x1a0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x12f/0x500 arch/x86/kernel/apic/apic.c:1137
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
 </IRQ>
RIP: 0010:default_idle+0x28/0x2e0 arch/x86/kernel/process.c:581
Code: 90 90 41 56 41 55 65 44 8b 2d f4 00 92 7a 41 54 55 53 0f 1f 44 00 00  
e8 c6 b2 d3 fb e9 07 00 00 00 0f 00 2d ea a5 52 00 fb f4 <65> 44 8b 2d d0  
00 92 7a 0f 1f 44 00 00 5b 5d 41 5c 41 5d 41 5e c3
RSP: 0018:ffff8881da22fdc8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000007 RBX: ffff8881da213000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8881da21384c
RBP: ffffed103b442600 R08: ffff8881da213000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
 cpuidle_idle_call kernel/sched/idle.c:154 [inline]
 do_idle+0x3b6/0x500 kernel/sched/idle.c:263
 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:355
 start_secondary+0x27d/0x330 arch/x86/kernel/smpboot.c:264
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241
Modules linked in:
---[ end trace e6cab2429e956502 ]---
RIP: 0010:transfer drivers/usb/gadget/udc/dummy_hcd.c:1426 [inline]
RIP: 0010:dummy_timer+0xad5/0x2fa2 drivers/usb/gadget/udc/dummy_hcd.c:1950
Code: 0f 84 f5 fd ff ff e8 2a 54 ab fd 89 de 44 89 e7 e8 10 55 ab fd 41 39  
dc 0f 82 b0 08 00 00 e8 12 54 ab fd 44 89 e0 31 d2 31 ff <f7> f3 89 d6 89  
94 24 c0 00 00 00 e8 6b 55 ab fd 8b 94 24 c0 00 00
RSP: 0018:ffff8881db309b20 EFLAGS: 00010046
RAX: 0000000000000040 RBX: 0000000000000000 RCX: ffffffff8392c490
RDX: 0000000000000000 RSI: ffffffff8392c49e RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff8881da213000 R09: ffffed103b661353
R10: ffffed103b661352 R11: 0000000000000003 R12: 0000000000000040
R13: ffff8881d4712a00 R14: dffffc0000000000 R15: ffff8881d20a2200
FS:  0000000000000000(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb31aad7000 CR3: 00000001d4b0e000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


Tested on:

commit:         22be26f7 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=17b3e44ce00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5fe29bc39eff9627
dashboard link: https://syzkaller.appspot.com/bug?extid=8ab8bf161038a8768553
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
patch:          https://syzkaller.appspot.com/x/patch.diff?x=15ea0a97600000