Re: general protection fault in rose_send_frame

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    7a25c6c0aac8 rocker: Add missing break for PRE_BRIDGE_FLAGS
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=104002d8c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=58cb9d752ba5f3e0
dashboard link: https://syzkaller.appspot.com/bug?extid=7078ae989d857fe17988
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1224c304c00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=151824f8c00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7078ae989d857fe17988@xxxxxxxxxxxxxxxxxxxxxxxxx

IPv6: ADDRCONF(NETDEV_CHANGE): hsr_slave_1: link becomes ready
8021q: adding VLAN 0 to HW filter on device batadv0
IPv6: ADDRCONF(NETDEV_CHANGE): rose0: link becomes ready
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.0.0-rc7+ #76
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:rose_send_frame+0x1a8/0x280 net/rose/rose_link.c:104
Code: c1 ea 03 80 3c 02 00 0f 85 8d 00 00 00 48 b8 00 00 00 00 00 fc ff df  
4c 8b 63 20 49 8d bc 24 58 03 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75  
7e 49 8b 94 24 58 03 00 00 e9 b8 fe ff ff e8 f0 53
RSP: 0018:ffff8880ae807ae8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff88809aa1fa00 RCX: ffffffff86378efb
RDX: 000000000000006b RSI: ffffffff8637902c RDI: 0000000000000358
RBP: ffff8880ae807b18 R08: ffffffff8887dec0 R09: ffffed101263146d
R10: ffffed101263146c R11: ffff88809318a363 R12: 0000000000000000
R13: 0000000000000078 R14: 0000000000000005 R15: ffff8880a4f6fbc0
FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f23b3e4ee78 CR3: 000000009eef3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 rose_transmit_clear_request+0x1de/0x2a0 net/rose/rose_link.c:258
 rose_rx_call_request+0x4ea/0x1990 net/rose/af_rose.c:1001
 rose_loopback_timer+0x26a/0x3f0 net/rose/rose_loopback.c:100
 call_timer_fn+0x190/0x720 kernel/time/timer.c:1325
 expire_timers kernel/time/timer.c:1362 [inline]
 __run_timers kernel/time/timer.c:1681 [inline]
 __run_timers kernel/time/timer.c:1649 [inline]
 run_timer_softirq+0x652/0x1700 kernel/time/timer.c:1694
 __do_softirq+0x266/0x95a kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x180/0x1d0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1062
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
 </IRQ>
RIP: 0010:native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:58
Code: ff ff ff 48 89 c7 48 89 45 d8 e8 59 6c a1 fa 48 8b 45 d8 e9 ce fe ff  
ff 48 89 df e8 48 6c a1 fa eb 82 90 90 90 90 90 90 fb f4 <c3> 0f 1f 00 66  
2e 0f 1f 84 00 00 00 00 00 f4 c3 90 90 90 90 90 90
RSP: 0018:ffffffff88807d08 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff1125061 RBX: ffffffff8887dec0 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffffffff8887e73c
RBP: ffffffff88807d38 R08: ffffffff8887dec0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff889282f8 R14: 0000000000000000 R15: 0000000000000000
 arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555
 default_idle_call+0x36/0x90 kernel/sched/idle.c:93
 cpuidle_idle_call kernel/sched/idle.c:153 [inline]
 do_idle+0x386/0x570 kernel/sched/idle.c:262
 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353
 rest_init+0x245/0x37b init/main.c:442
 arch_call_rest_init+0xe/0x1b
 start_kernel+0x803/0x83c init/main.c:739
 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
Modules linked in:
---[ end trace 8f29030702ddb052 ]---
RIP: 0010:rose_send_frame+0x1a8/0x280 net/rose/rose_link.c:104
Code: c1 ea 03 80 3c 02 00 0f 85 8d 00 00 00 48 b8 00 00 00 00 00 fc ff df  
4c 8b 63 20 49 8d bc 24 58 03 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75  
7e 49 8b 94 24 58 03 00 00 e9 b8 fe ff ff e8 f0 53
RSP: 0018:ffff8880ae807ae8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff88809aa1fa00 RCX: ffffffff86378efb
RDX: 000000000000006b RSI: ffffffff8637902c RDI: 0000000000000358
RBP: ffff8880ae807b18 R08: ffffffff8887dec0 R09: ffffed101263146d
R10: ffffed101263146c R11: ffff88809318a363 R12: 0000000000000000
R13: 0000000000000078 R14: 0000000000000005 R15: ffff8880a4f6fbc0
FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f23b3e4ee78 CR3: 000000009eef3000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400