BUG: kernel NULL pointer dereference, address: 000000000000009c #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 20e99067 P4D 20e99067 PUD 20e9a067 PMD 0 Oops: 0000 [#1] PREEMPT SMP CPU: 1 PID: 3159 Comm: kworker/u4:4 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:ffffc900061b3bf8 EFLAGS: 00010046 RAX: 000000000000009c RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000003 R08: 00000000aaaaaaab R09: 000800000000009c R10: 0000000000000246 R11: ffff8881019ac040 R12: 0000000000000004 R13: 0000000000000000 R14: ffff88810cbbe240 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000000009c CR3: 0000000020e98000 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+0x435/0x8a0 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 fc4882af00d8897d ]--- 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:ffffc900061b3bf8 EFLAGS: 00010046 RAX: 000000000000009c RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000003 R08: 00000000aaaaaaab R09: 000800000000009c R10: 0000000000000246 R11: ffff8881019ac040 R12: 0000000000000004 R13: 0000000000000000 R14: ffff88810cbbe240 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000000009c CR3: 0000000020e98000 CR4: 00000000001506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400