Re: Bug inkvm_set_irq

[Jean-Philippe Menil <jean-philippe.menil@univ-nantes.fr>]

Le 03/03/2011 15:47, Michael S. Tsirkin a écrit :
> On Tue, Mar 01, 2011 at 03:39:12PM +0100, Jean-Philippe Menil wrote:
>> so this time the bug is:
>>
>> [17882.612303] BUG: unable to handle kernel paging request at
>> 0000000000002458
>> [17882.612342] IP: [<ffffffffa03898a0>] kvm_set_irq+0x30/0x140 [kvm]
>>
>> markup_oops give me this:
>>
>> root@ayrshire:~# cat bug-0103.txt | perl markup_oops.pl -m
>> /lib/modules/2.6.37.2-dsiun-110105+/kernel/arch/x86/kvm/kvm.ko
>> /boot/vmlinuz-2.6.37.2-dsiun-110105+
>> vmaoffset = 18446744072102621184 ffffffffa0389871:	48 89 e5   	mov
>> %rsp,%rbp
>>   ffffffffa0389874:	41 57                	push   %r15
>>   ffffffffa0389876:	41 89 cf             	mov    %ecx,%r15d  |  %r15
>> =>  1  %ecx = 1
>>   ffffffffa0389879:	41 56                	push   %r14        |  %r14
>> =>  ffffffffa038aad0
>>   ffffffffa038987b:	41 55                	push   %r13
>>   ffffffffa038987d:	49 89 fd             	mov    %rdi,%r13   |  %edi
>> = 0  %r13 =>  0
>>   ffffffffa0389880:	41 54                	push   %r12        |  %r12 =>  0
>>   ffffffffa0389882:	53                   	push   %rbx
>>   ffffffffa0389883:	89 d3                	mov    %edx,%ebx   |  %ebx =>  1a
>>   ffffffffa0389885:	48 81 ec a8 00 00 00 	sub    $0xa8,%rsp
>>   ffffffffa038988c:	8b 15 00 00 00 00    	mov    0x0(%rip),%edx
>> # ffffffffa0389892<kvm_set_irq+0x22>
>>   ffffffffa0389892:	89 b5 3c ff ff ff    	mov    %esi,-0xc4(%rbp) |
>> %esi = 0
>>   ffffffffa0389898:	85 d2                	test   %edx,%edx   |  %edx =>  0
>>   ffffffffa038989a:	0f 85 d5 00 00 00    	jne    ffffffffa0389975
>> <kvm_set_irq+0x105>
>> *ffffffffa03898a0:	49 8b 85 58 24 00 00 	mov    0x2458(%r13),%rax |
>> %eax = 0  %r13 = 0<--- faulting instruction
>>   ffffffffa03898a7:	3b 98 28 01 00 00    	cmp    0x128(%rax),%ebx
>>   ffffffffa03898ad:	73 61                	jae    ffffffffa0389910
>> <kvm_set_irq+0xa0>
>>   ffffffffa03898af:	89 db                	mov    %ebx,%ebx
>>   ffffffffa03898b1:	48 8b 84 d8 30 01 00 	mov    0x130(%rax,%rbx,8),%rax
>>   ffffffffa03898b8:	00
>>   ffffffffa03898b9:	48 85 c0             	test   %rax,%rax
>>   ffffffffa03898bc:	74 52                	je     ffffffffa0389910
>> <kvm_set_irq+0xa0>
>>   ffffffffa03898be:	48 8d 95 40 ff ff ff 	lea    -0xc0(%rbp),%rdx
>>   ffffffffa03898c5:	31 db                	xor    %ebx,%ebx
>>   ffffffffa03898c7:	48 8b 08             	mov    (%rax),%rcx
>>   ffffffffa03898ca:	83 c3 01             	add    $0x1,%ebx
>>   ffffffffa03898cd:	0f 18 09             	prefetcht0 (%rcx)
>>   ffffffffa03898d0:	48 8b 48 e0          	mov    -0x20(%rax),%rcx
>>   ffffffffa03898d4:	48 89 0a             	mov    %rcx,(%rdx)
>>   ffffffffa03898d7:	48 8b 48 e8          	mov    -0x18(%rax),%rcx
>>   ffffffffa03898db:	48 89 4a 08          	mov    %rcx,0x8(%rdx)
>>   ffffffffa03898df:	48 8b 48 f0          	mov    -0x10(%rax),%rcx
>>   ffffffffa03898e3:	48 89 4a 10          	mov    %rcx,0x10(%rdx)
>>   ffffffffa03898e7:	48 8b 48 f8          	mov    -0x8(%rax),%rcx
>>   ffffffffa03898eb:	48 89 4a 18          	mov    %rcx,0x18(%rdx)
>>
>> wich correspond to offset 68a0 (from objdump):
>>
>> kvm_set_irq():
>> /usr/src/GIT/linux-2.6-stable/arch/x86/kvm/../../../virt/kvm/irq_comm.c:161
>>      68a0:       49 8b 85 58 24 00 00    mov    0x2458(%r13),%rax
>> /usr/src/GIT/linux-2.6-stable/arch/x86/kvm/../../../virt/kvm/irq_comm.c:162
>>      68a7:       3b 98 28 01 00 00       cmp    0x128(%rax),%ebx
>>
>> root@ayrshire:~# addr2line -e
>> /lib/modules/2.6.37.2-dsiun-110105+/kernel/arch/x86/kvm/kvm.ko
>> 0x68a0
>> /usr/src/GIT/linux-2.6-stable/arch/x86/kvm/../../../virt/kvm/irq_comm.c:161
>>
>> So here kvm->irq_routing is null.
>>
>> How can it be?
>>
>> Regards.
> Not null, this seems to be invalid.
> I suspect use after free where the kvm pointer is
> pointing at some random memory. Use after free?
> Could you please try enabling a slab debugger,
> recompile and rerun the test?
>
Hi,

I'm not sure to activate the right thing.
Is that what you want?

CONFIG_SLAB=y
CONFIG_SLABINFO=y
CONFIG_DEBUG_SLAB=y
CONFIG_DEBUG_SLAB_LEAK=y

Regards.

-- 
Jean-Philippe Menil - Pôle réseau Service IRTS
DSI Université de Nantes
jean-philippe.menil@univ-nantes.fr
Tel : 02.53.48.49.27 - Fax : 02.53.48.49.09