BUG: unable to handle kernel paging request in batadv_nc_purge_paths

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 877cd9ff Merge branch 'net-dsa-use-switchdev-attr-and-obj-..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17ff3b6aa00000
kernel config: https://syzkaller.appspot.com/x/.config?x=f7a0e5816ab80450
dashboard link: https://syzkaller.appspot.com/bug?extid=b1b8f4196e00e7fcfb2e
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [a...@unstable.cc b.a.t...@lists.open-mesh.org
da...@davemloft.net linux-...@vger.kernel.org marekl...@neomailbox.ch
net...@vger.kernel.org s...@simonwunderlich.de net...@vger.kernel.org]

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+b1b8f4...@syzkaller.appspotmail.com

BUG: unable to handle page fault for address: ffff88808ba40480
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD b401067 P4D b401067 PUD 21ffff067 PMD 9645e063 PTE ffffffff8b1de200
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9967 Comm: kworker/u4:7 Not tainted 5.2.0-rc3+ #32
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
RIP: 0010:batadv_nc_purge_paths+0xea/0x370
net/batman-adv/network-coding.c:442
Code: 48 8b 45 c8 48 6b db 38 48 03 58 08 48 89 df 48 89 5d b8 e8 88 85 1c
00 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 0f 85 e0 01 00 00 <4d> 8b 24 24 eb
30 e8 8b d4 6d fa e8 86 2e 86 fe 31 ff 41 89 c7 89
RSP: 0018:ffff888066537c60 EFLAGS: 00010246
RAX: 1ffff11011748090 RBX: ffff88809381dc40 RCX: ffffffff81585bea
RDX: 1ffff11012703b8a RSI: 0000000000000004 RDI: ffff888066537bc8
RBP: ffff888066537cd0 R08: 1ffff1100cca6f79 R09: ffffed100cca6f7a
R10: ffffed100cca6f79 R11: 0000000000000003 R12: ffff88808ba40480
R13: dffffc0000000000 R14: ffffffff8702de10 R15: ffff8880a13c43c0
FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff88808ba40480 CR3: 000000006836a000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
batadv_nc_worker+0x29c/0x760 net/batman-adv/network-coding.c:719
process_one_work+0x989/0x1790 kernel/workqueue.c:2269
worker_thread+0x98/0xe40 kernel/workqueue.c:2415
kthread+0x354/0x420 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
CR2: ffff88808ba40480
---[ end trace 12a529f611a917cc ]---
RIP: 0010:batadv_nc_purge_paths+0xea/0x370
net/batman-adv/network-coding.c:442
Code: 48 8b 45 c8 48 6b db 38 48 03 58 08 48 89 df 48 89 5d b8 e8 88 85 1c
00 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 0f 85 e0 01 00 00 <4d> 8b 24 24 eb
30 e8 8b d4 6d fa e8 86 2e 86 fe 31 ff 41 89 c7 89
RSP: 0018:ffff888066537c60 EFLAGS: 00010246
RAX: 1ffff11011748090 RBX: ffff88809381dc40 RCX: ffffffff81585bea
RDX: 1ffff11012703b8a RSI: 0000000000000004 RDI: ffff888066537bc8
RBP: ffff888066537cd0 R08: 1ffff1100cca6f79 R09: ffffed100cca6f7a
R10: ffffed100cca6f79 R11: 0000000000000003 R12: ffff88808ba40480
R13: dffffc0000000000 R14: ffffffff8702de10 R15: ffff8880a13c43c0
FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff88808ba40480 CR3: 000000006836a000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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 syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.