BUG: kernel NULL pointer dereference, address: 000000000000009c
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 9457d067 P4D 9457d067 PUD 71a4c067 PMD 0 
Oops: 0000 [#1] PREEMPT SMP
CPU: 1 PID: 3297 Comm: kworker/u4:5 Not tainted 5.10.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
RIP: 0010:kcsan_setup_watchpoint+0x215/0x4d0 kernel/kcsan/core.c:479
Code: 9d 4c 89 74 24 50 eb 05 ff 74 24 50 9d 48 83 c4 60 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f b7 08 89 ca c1 ea 08 31 db 31 f6 eb 26 <8b> 08 89 ca c1 ea 08 89 ce c1 ee 10 eb 18 48 8b 08 48 89 ca 48 c1
RSP: 0018:ffffc90006263bf8 EFLAGS: 00010046
RAX: 000000000000009c RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 00000000aaaaaaab R09: 000800000000009c
R10: 0000000000000246 R11: 0000000000000216 R12: 0000000000000004
R13: 0000000000000000 R14: 0000ffff86a63f38 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000000009c CR3: 0000000051b84000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 afs_unuse_cell+0x24/0x2b0 fs/afs/cell.c:592
 afs_cell_purge+0x72/0x1e0 fs/afs/cell.c:951
 afs_net_exit+0x67/0xa0 fs/afs/main.c:156
 ops_exit_list net/core/net_namespace.c:187 [inline]
 cleanup_net+0x45e/0x8a0 net/core/net_namespace.c:604
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1fa/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
Modules linked in:
CR2: 000000000000009c
---[ end trace 63744ea75bd59619 ]---
RIP: 0010:kcsan_setup_watchpoint+0x215/0x4d0 kernel/kcsan/core.c:479
Code: 9d 4c 89 74 24 50 eb 05 ff 74 24 50 9d 48 83 c4 60 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f b7 08 89 ca c1 ea 08 31 db 31 f6 eb 26 <8b> 08 89 ca c1 ea 08 89 ce c1 ee 10 eb 18 48 8b 08 48 89 ca 48 c1
RSP: 0018:ffffc90006263bf8 EFLAGS: 00010046
RAX: 000000000000009c RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 00000000aaaaaaab R09: 000800000000009c
R10: 0000000000000246 R11: 0000000000000216 R12: 0000000000000004
R13: 0000000000000000 R14: 0000ffff86a63f38 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000000009c CR3: 0000000051b84000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400