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Date: Tue, 6 May 2014 13:08:38 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Sasha Levin <sasha.levin@...cle.com>
Cc: Ingo Molnar <mingo@...nel.org>, Mel Gorman <mgorman@...e.de>,
LKML <linux-kernel@...r.kernel.org>,
Dave Jones <davej@...hat.com>
Subject: Re: sched,numa: invalid memory access in account_entity_dequeue
On Sat, May 03, 2014 at 09:16:00AM -0400, Sasha Levin wrote:
> Hi all,
>
> While fuzzing with trinity inside a KVM tools guest running latest -next
> kernel I've stumbled on the following:
>
Cute.. not making sense.. :-)
> [ 1796.591361] BUG: unable to handle kernel paging request at fffffffedf97f040
> [ 1796.592665] IP: __cpu_to_node (arch/x86/mm/numa.c:777)
I suppose you've scripted this addr2line -ie vmlinux for all addresses
in this splat?
> [ 1796.593710] PGD 21e30067 PUD 0
> [ 1796.594174] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [ 1796.594937] Dumping ftrace buffer:
> [ 1796.595678] (ftrace buffer empty)
> [ 1796.596329] Modules linked in:
> [ 1796.596733] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G W 3.15.0-rc3-next-20140502-sasha-00019-g5cb1c98 #431
> [ 1796.598143] task: ffff8803345b8000 ti: ffff880035fc0000 task.ti: ffff880035fc0000
> [ 1796.598975] RIP: __cpu_to_node (arch/x86/mm/numa.c:777)
> [ 1796.600093] RSP: 0018:ffff8800a6c03b88 EFLAGS: 00010046
> [ 1796.600197] RAX: ffff8806e791a000 RBX: ffffffffe791a028 RCX: 0000000000000000
> [ 1796.600197] RDX: 0000000000000001 RSI: ffff8806cdc68068 RDI: 00000000e791a028
> [ 1796.600197] RBP: ffff8800a6c03b98 R08: ffff880496183078 R09: 00000000000151c6
> [ 1796.600197] R10: 000000000000b731 R11: 0000000000000001 R12: ffff8801b4dd7840
> [ 1796.600197] R13: 0000000000000000 R14: 000000000000001e R15: ffff8801b34ac1a0
> [ 1796.600197] FS: 0000000000000000(0000) GS:ffff8800a6c00000(0000) knlGS:0000000000000000
> [ 1796.600197] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [ 1796.600197] CR2: fffffffedf97f040 CR3: 0000000021e2d000 CR4: 00000000000006a0
> [ 1796.610323] Stack:
> [ 1796.610323] 0000000000000000 ffff8801b34ac1a0 ffff8800a6c03bd8 ffffffff9d1a9646
> [ 1796.610323] ffff8800a6c03bd8 ffff8806cdc68068 ffff8806cdc68068 ffff8801b34ac1a0
> [ 1796.610323] 0000000000000000 000000000000b7db ffff8800a6c03c38 ffffffff9d1ae987
> [ 1796.610323] Call Trace:
> [ 1796.610323] <IRQ>
> [ 1796.610323] account_entity_dequeue (kernel/sched/fair.c:859 kernel/sched/fair.c:2009)
> [ 1796.610323] dequeue_entity (kernel/sched/fair.c:2827)
> [ 1796.610323] dequeue_task_fair (kernel/sched/fair.c:3907 include/linux/jump_label.h:105 kernel/sched/fair.c:3041 kernel/sched/fair.c:3217 kernel/sched/fair.c:3915)
> [ 1796.610323] dequeue_task (kernel/sched/core.c:793)
> [ 1796.610323] deactivate_task (kernel/sched/core.c:809)
> [ 1796.610323] move_task (kernel/sched/fair.c:5032)
> [ 1796.610323] load_balance (kernel/sched/fair.c:5305 kernel/sched/fair.c:6485)
> [ 1796.610323] ? debug_smp_processor_id (lib/smp_processor_id.c:57)
> [ 1796.610323] rebalance_domains (kernel/sched/fair.c:7032)
> [ 1796.610323] ? rebalance_domains (kernel/sched/fair.c:6975)
> [ 1796.610323] run_rebalance_domains (kernel/sched/fair.c:7105 kernel/sched/fair.c:7198)
> [ 1796.610323] __do_softirq (kernel/softirq.c:269 include/linux/jump_label.h:105 include/trace/events/irq.h:126 kernel/softirq.c:270)
> [ 1796.610323] ? irq_exit (include/linux/vtime.h:82 include/linux/vtime.h:121 kernel/softirq.c:384)
> [ 1796.610323] irq_exit (kernel/softirq.c:346 kernel/softirq.c:387)
> [ 1796.610323] scheduler_ipi (kernel/sched/core.c:1545)
> [ 1796.610323] smp_reschedule_interrupt (arch/x86/kernel/smp.c:266)
> [ 1796.610323] reschedule_interrupt (arch/x86/kernel/entry_64.S:1178)
> [ 1796.610323] <EOI>
> [ 1796.610323] ? native_safe_halt (arch/x86/include/asm/irqflags.h:50)
> [ 1796.610323] ? trace_hardirqs_on (kernel/locking/lockdep.c:2607)
> [ 1796.637135] default_idle (arch/x86/include/asm/paravirt.h:111 arch/x86/kernel/process.c:310)
> [ 1796.637135] arch_cpu_idle (arch/x86/kernel/process.c:302)
> [ 1796.637135] cpu_idle_loop (kernel/sched/idle.c:179 kernel/sched/idle.c:226)
> [ 1796.637135] cpu_startup_entry (??:?)
> [ 1796.637135] start_secondary (arch/x86/kernel/smpboot.c:267)
> [ 1796.637135] Code: 3a ea 05 00 74 25 89 de 48 c7 c7 08 b4 6c a1 31 c0 e8 99 6c 45 03 e8 7c 39 46 03 48 8b 05 71 3a ea 05 8b 04 98 eb 16 0f 1f 40 00 <48> 8b 14 dd 00 ef 0a a3 48 c7 c0 d8 f4 00 00 8b 04 10 48 83 c4
Could you maybe also do the same with the Code? -- that is, script an
auto-decode for it?
Obviously scripts/decodecode doesn't actually work right anymore:
# echo [ 1796.637135] Code: 3a ea 05 00 74 25 89 de 48 c7 c7 08 b4 6c a1 31 c0 e8 99 6c 45 03 e8 7c 39 46 03 48 8b 05 71 3a ea 05 8b 04 98 eb 16 0f 1f 40 00 <48> 8b 14 dd 00 ef 0a a3 48 c7 c0 d8 00 00 8b 04 10 48 83 c4 | ./scripts/decodecode
-bash: syntax error near unexpected token `48'
But if I remove the <> by hand I get:
# echo [ 1796.637135] Code: 3a ea 05 00 74 25 89 de 48 c7 c7 08 b4 6c a1 31 c0 e8 99 6c 45 03 e8 7c 39 46 03 48 8b 05 71 3a ea 05 8b 04 98 eb 16 0f 1f 40 00 48 8b 14 dd 00 ef 0a a3 48 c7 c0 d8 00 00 8b 04 10 48 83 c4 | ./scripts/decodecode
[ 1796.637135] Code: 3a ea 05 00 74 25 89 de 48 c7 c7 08 b4 6c a1 31 c0 e8 99 6c 45 03 e8 7c 39 46 03 48 8b 05 71 3a ea 05 8b 04 98 eb 16 0f 1f 40 00 48 8b 14 dd 00 ef 0a a3 48 c7 c0 d8 00 00 8b 04 10 48 83 c4
sed: -e expression #1, char 1: unknown command: `-'
Code starting with the faulting instruction
===========================================
0: 3a ea cmp %dl,%ch
2: 05 00 74 25 89 add $0x89257400,%eax
7: de 48 c7 fimul -0x39(%rax)
a: c7 (bad)
b: 08 b4 6c a1 31 c0 e8 or %dh,-0x173fce5f(%rsp,%rbp,2)
12: 99 cltd
13: 6c insb (%dx),%es:(%rdi)
14: 45 03 e8 add %r8d,%r13d
17: 7c 39 jl 0x52
19: 46 03 48 8b rex.RX add -0x75(%rax),%r9d
1d: 05 71 3a ea 05 add $0x5ea3a71,%eax
22: 8b 04 98 mov (%rax,%rbx,4),%eax
25: eb 16 jmp 0x3d
27: 0f 1f 40 00 nopl 0x0(%rax)
2b: 48 8b 14 dd 00 ef 0a mov -0x5cf51100(,%rbx,8),%rdx
32: a3
33: 48 c7 c0 d8 00 00 8b mov $0xffffffff8b0000d8,%rax
3a: 04 10 add $0x10,%al
3c: 48 rex.W
3d: 83 .byte 0x83
3e: c4 .byte 0xc4
And 2b is the offset where the <> was.
Anyway, the reason I did this was that I was hoping to find
the cpu argument in one of the registers, but looking at your RBX value
doesn't really help.
If I compile this function with a defconfig based .config, I get
something like:
00000000000000a0 <__cpu_to_node>:
a0: 48 83 3d 00 00 00 00 cmpq $0x0,0x0(%rip) # a8 <__cpu_to_node+0x8>
a7: 00
a8: 55 push %rbp
a9: 48 89 e5 mov %rsp,%rbp
ac: 53 push %rbx
ad: 48 63 df movslq %edi,%rbx
b0: 75 15 jne c7 <__cpu_to_node+0x27>
b2: 48 8b 14 dd 00 00 00 mov 0x0(,%rbx,8),%rdx
b9: 00
ba: 48 c7 c0 00 00 00 00 mov $0x0,%rax
c1: 8b 04 10 mov (%rax,%rdx,1),%eax
c4: 5b pop %rbx
c5: 5d pop %rbp
c6: c3 retq
c7: 89 de mov %ebx,%esi
c9: 48 c7 c7 00 00 00 00 mov $0x0,%rdi
d0: 31 c0 xor %eax,%eax
d2: e8 00 00 00 00 callq d7 <__cpu_to_node+0x37>
d7: e8 00 00 00 00 callq dc <__cpu_to_node+0x3c>
dc: 48 8b 05 00 00 00 00 mov 0x0(%rip),%rax # e3 <__cpu_to_node+0x43>
e3: 8b 04 98 mov (%rax,%rbx,4),%eax
e6: eb dc jmp c4 <__cpu_to_node+0x24>
e8: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1)
ef: 00
And the b2 offset matches up fairly nicely, although the rest of the
decode appears to be crap. Still no hints though.
However, calling convention puts the first argument in EAX, and at b2
EAX should still contain the original value, however your RAX value is
complete nonsense again :/
Of course, the cpu argument being complete crap is a good reason for
this to happen. Which would make thread_info::cpu of the task in
question be complete crap.. and I'm not sure I can explain that either.
la-la-la..
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