Here's another one if it helps:

[848423.023156] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
[848423.023180] IP: [<ffffffff8130d7f1>] rb_next+0x1/0x50
[848423.023194] PGD 18ad83067 PUD 18ad82067 PMD 0 
[848423.023203] Oops: 0000 [#1] SMP 
[848423.023210] CPU 1 
[848423.023213] Modules linked in: ipt_REJECT xt_tcpudp nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack iptable_filter ip_tables x_tables parport_pc ppdev lp parport isofs acpiphp
[848423.023245] 
[848423.023249] Pid: 18572, comm: chef-client Not tainted 3.2.0-24-virtual #37-Ubuntu  
[848423.023258] RIP: e030:[<ffffffff8130d7f1>]  [<ffffffff8130d7f1>] rb_next+0x1/0x50
[848423.023267] RSP: e02b:ffff88018af21c18  EFLAGS: 00010046
[848423.023273] RAX: 0000000000000000 RBX: ffff8801a125ce00 RCX: 0000000000000000
[848423.023278] RDX: fffffffffffffff0 RSI: 0000000000000000 RDI: 0000000000000010
[848423.023285] RBP: ffff88018af21c48 R08: 0000000000000000 R09: 0000000000000000
[848423.023291] R10: ffff8801dff866c0 R11: 0000000000000001 R12: 0000000000000000
[848423.023299] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000003a5a9d0
[848423.023311] FS:  00007fb6bdc16700(0000) GS:ffff8801dff8f000(0000) knlGS:0000000000000000
[848423.023319] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
[848423.023325] CR2: 0000000000000010 CR3: 00000001a12e8000 CR4: 0000000000002660
[848423.023332] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[848423.023339] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[848423.023346] Process chef-client (pid: 18572, threadinfo ffff88018af20000, task ffff8801a12f8000)
[848423.023353] Stack:
[848423.023356]  ffff88018af21c48 ffffffff8104ece9 ffff8801a125ce00 ffff8801dffa26c0
[848423.023369]  ffff8801d29cc600 0000000000000000 ffff88018af21c78 ffffffff810544b8
[848423.023380]  ffff88018af21c78 ffff8801dffa26c0 0000000000000001 ffff8801a12f83a8
[848423.023392] Call Trace:
[848423.023402]  [<ffffffff8104ece9>] ? pick_next_entity+0xb9/0xe0
[848423.023410]  [<ffffffff810544b8>] pick_next_task_fair+0x38/0x70
[848423.023419]  [<ffffffff81652ddc>] __schedule+0x14c/0x6f0
[848423.023426]  [<ffffffff816554ee>] ? _raw_spin_unlock_irqrestore+0x1e/0x30
[848423.023433]  [<ffffffff8165344f>] schedule+0x3f/0x60
[848423.023441]  [<ffffffff8117e119>] pipe_wait+0x59/0x80
[848423.023449]  [<ffffffff81089340>] ? add_wait_queue+0x60/0x60
[848423.023456]  [<ffffffff8117e87a>] pipe_read+0x1da/0x330
[848423.023463]  [<ffffffff81174522>] do_sync_read+0xd2/0x110
[848423.023471]  [<ffffffff8100a25d>] ? xen_force_evtchn_callback+0xd/0x10
[848423.023478]  [<ffffffff8100aa32>] ? check_events+0x12/0x20
[848423.023486]  [<ffffffff81298d33>] ? security_file_permission+0x93/0xb0
[848423.023493]  [<ffffffff811749a1>] ? rw_verify_area+0x61/0xf0
[848423.023499]  [<ffffffff81174e80>] vfs_read+0xb0/0x180
[848423.023505]  [<ffffffff81174f9a>] sys_read+0x4a/0x90
[848423.023513]  [<ffffffff8165d8c2>] system_call_fastpath+0x16/0x1b
[848423.023518] Code: 89 06 48 8b 47 08 48 89 46 08 48 8b 47 10 48 89 46 10 c3 0f 1f 80 00 00 00 00 48 89 32 eb b2 0f 1f 00 48 89 70 10 eb a9 66 90 55 <48> 8b 17 48 89 e5 48 89 d0 48 83 e0 fc 48 39 c7 74 34 48 8b 47 
[848423.023608] RIP  [<ffffffff8130d7f1>] rb_next+0x1/0x50
[848423.023615]  RSP <ffff88018af21c18>
[848423.023619] CR2: 0000000000000010
[848423.023637] ---[ end trace 5361bc1ec5930886 ]---