Subject: Re: bpf/asan related lockup

From: Daniel Borkmann <[email-masked]>
Date: Wed, 09 Dec 2015 23:24:32 +0100

On 12/04/2015 08:06 PM, Alexei Starovoitov wrote:
> On Fri, Dec 04, 2015 at 01:23:33PM -0500, Dave Jones wrote:
>> Trinity had aparently created a bpf program that upset things greatly.
>> I guess I need to find a way to make it record those somewhere for replaying later.
>>
>> Alexei, any ideas ?
>>
>> 	Dave
>>
>> NMI watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [kworker/0:1:991]
>> irq event stamp: 153214
>> hardirqs last  enabled at (153213): [<ffffffffa0cb390c>] _raw_spin_unlock_irq+0x2c/0x50
>> hardirqs last disabled at (153214): [<ffffffffa0cb35c9>] _raw_spin_lock_irq+0x19/0x80
>> softirqs last  enabled at (153108): [<ffffffffa00b32f8>] __do_softirq+0x2b8/0x590
>> softirqs last disabled at (153103): [<ffffffffa00b3805>] irq_exit+0xf5/0x100
>> CPU: 0 PID: 991 Comm: kworker/0:1 Tainted: G      D W       4.4.0-rc3-think+ #5
>> Workqueue: events bpf_prog_free_deferred
>> task: ffff880464dab700 ti: ffff8803041d8000 task.ti: ffff8803041d8000
>> RIP: 0010:[<ffffffffa02d6950>]  [<ffffffffa02d6950>] __asan_load4+0x0/0x70
>> RSP: 0018:ffff8803041dfa08  EFLAGS: 00000202
>> RAX: 0000000000000003 RBX: ffff880468be39a8 RCX: 0000000000000000
>> RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffff880468be39c0
>> RBP: ffff8803041dfa70 R08: 0000000000000000 R09: 0000000000000001
>> R10: ffff8803041dfb8f R11: 0000000000000000 R12: ffff880468be39c0
>> R13: 0000000000000001 R14: ffff8804689dff00 R15: 0000000000000001
>> FS:  0000000000000000(0000) GS:ffff880468800000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 00007faeedb04000 CR3: 0000000452548000 CR4: 00000000001406f0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
>> Stack:
>>   ffffffffa018f2ce 00000000001dfec0 01ff880300000001 ffff8803041dfaf8
>>   ffffffffa0076610 ffffffffa18895d8 ffff8804689dff08 0000000000000004
>>   ffffffffa0076610 ffff8803041dfaf8 0000000000000001 ffffc90000171000
>> Call Trace:
>>   [<ffffffffa018f2ce>] ? smp_call_function_many+0x32e/0x410
>>   [<ffffffffa0076610>] ? rbt_memtype_copy_nth_element+0xd0/0xd0
>>   [<ffffffffa0076610>] ? rbt_memtype_copy_nth_element+0xd0/0xd0
>>   [<ffffffffa018f3f7>] smp_call_function+0x47/0x80
>>   [<ffffffffa0076610>] ? rbt_memtype_copy_nth_element+0xd0/0xd0
>>   [<ffffffffa018f45f>] on_each_cpu+0x2f/0x90
>>   [<ffffffffa0077a10>] flush_tlb_kernel_range+0xc0/0xd0
>>   [<ffffffffa0077950>] ? flush_tlb_all+0x20/0x20
>>   [<ffffffffa02b547f>] remove_vm_area+0xaf/0x100
>>   [<ffffffffa02b5506>] __vunmap+0x36/0x180
>>   [<ffffffffa02b56c5>] vfree+0x35/0xa0
>>   [<ffffffffa0229867>] __bpf_prog_free+0x27/0x30
>>   [<ffffffffa00a4da9>] bpf_jit_free+0x69/0x6e
>>   [<ffffffffa022988f>] bpf_prog_free_deferred+0x1f/0x30
>>   [<ffffffffa00d6d3a>] process_one_work+0x3fa/0xa10
>>   [<ffffffffa00d6c74>] ? process_one_work+0x334/0xa10
>>   [<ffffffffa00d6940>] ? pwq_dec_nr_in_flight+0x110/0x110
>>   [<ffffffffa00d73d8>] worker_thread+0x88/0x6c0
>
> hmm. may be set_memory_rw(ptr) followed by vfree(ptr) have a race
> deep inside mm logic.
> Both of them do flush_tlb_kernel_range()...

Hmm, was the rbt_memtype_copy_nth_element() by chance unrelated when this
happens or are we somehow stuck there each time? Only place where that can
be invoked is memtype_get_idx() when a cat /sys/kernel/debug/x86/pat_memtype_list
is done.