general protection fault in batadv_iv_ogm_queue_add

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    998d7551 Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1702db87600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e0ac4d9b35046343
dashboard link: https://syzkaller.appspot.com/bug?extid=7dd2da51d8ae6f990403
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7dd2da51d8ae6f990403@xxxxxxxxxxxxxxxxxxxxxxxxx

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: 4256 Comm: kworker/u4:0 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
RIP: 0010:batadv_iv_ogm_queue_add+0x49/0x1120  
net/batman-adv/bat_iv_ogm.c:605
Code: 48 89 75 b8 48 89 4d c0 4c 89 45 b0 44 89 4d d0 e8 fc 02 46 fa 48 8d  
7b 03 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 48  
89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 18 0d 00 00
RSP: 0018:ffff88805d2cfb80 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff888092284000
RDX: 0000000000000000 RSI: ffffffff872d1214 RDI: 0000000000000003
RBP: ffff88805d2cfc18 R08: ffff888092284000 R09: 0000000000000001
R10: ffffed100ba59f77 R11: 0000000000000003 R12: dffffc0000000000
R13: ffffed101245080e R14: ffff888092284000 R15: 0000000100051cf6
FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200002c0 CR3: 00000000a421b000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 batadv_iv_ogm_schedule+0xb0b/0xe50 net/batman-adv/bat_iv_ogm.c:813
 batadv_iv_send_outstanding_bat_ogm_packet+0x580/0x760  
net/batman-adv/bat_iv_ogm.c:1675
 process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace 04d065842187c2b8 ]---
RIP: 0010:batadv_iv_ogm_queue_add+0x49/0x1120  
net/batman-adv/bat_iv_ogm.c:605
Code: 48 89 75 b8 48 89 4d c0 4c 89 45 b0 44 89 4d d0 e8 fc 02 46 fa 48 8d  
7b 03 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 48  
89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 18 0d 00 00
RSP: 0018:ffff88805d2cfb80 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff888092284000
RDX: 0000000000000000 RSI: ffffffff872d1214 RDI: 0000000000000003
RBP: ffff88805d2cfc18 R08: ffff888092284000 R09: 0000000000000001
R10: ffffed100ba59f77 R11: 0000000000000003 R12: dffffc0000000000
R13: ffffed101245080e R14: ffff888092284000 R15: 0000000100051cf6
FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200002c0 CR3: 00000000a421b000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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