Re: [Qemu-devel] Ubuntu/Debian Installer + Virtio-BLK -> Bad ram pointer

[Peter Lieven <pl@dlhnet.de>]

On 30.10.2012 09:32, Stefan Hajnoczi wrote:
> On Mon, Oct 29, 2012 at 03:09:37PM +0100, Peter Lieven wrote:
>> Hi,
> Bug subject should be virtio-blk, not virtio-scsi.  virtio-scsi is a
> different virtio device type from virtoi-blk and is not present in the
> backtrace you posted.
you are right, sorry for that.
>
> Sounds pedantic but I want to make sure this gets chalked up against the
> right device :).
>
>> If I try to Install Ubuntu 12.04 LTS / 12.10 64-bit on a virtio
>> storage backend that supports iSCSI
>> qemu-kvm crashes reliably with the following error:
> Are you using vanilla qemu-kvm-1.2.0 or are there patches applied?
I use vanilla qemu-kvm 1.2.0 except for one virtio-blk related patch 
(CVE-2011-4127):
http://git.kernel.org/?p=virt/kvm/qemu-kvm.git;a=commit;h=1ba1f2e319afdcb485963cd3f426fdffd1b725f2
that for some reason did not made it into qemu-kvm 1.2.0 and two aio 
related patchs:
http://git.kernel.org/?p=virt/kvm/qemu-kvm.git;a=commit;h=00f78533326c5ba2e62fafada16655aa558a5520
http://git.kernel.org/?p=virt/kvm/qemu-kvm.git;a=commit;h=2db2bfc0ccac5fd68dbf0ceb70fbc372c5d8a8c7

this is why I can circumvent the issue with scsi=off i guess.
>
> Have you tried qemu-kvm.git/master?
not yet.
>
> Have you tried a local raw disk image to check whether libiscsi is
> involved?
I have, here it does not happen. For a raw device scsi is scsi=off, 
isn't it?
>
>> Bad ram pointer 0x3039303620008000
>>
>> This happens directly after the confirmation of the Timezone before
>> the Disk is partitioned.
>>
>> If I specify  -global virtio-blk-pci.scsi=off in the cmdline this
>> does not happen.
>>
>> Here is a stack trace:
>>
>> Thread 1 (Thread 0x7ffff7fee700 (LWP 8226)):
>> #0 0x00007ffff63c0a10 in abort () from /lib/x86_64-linux-gnu/libc.so.6
>> No symbol table info available.
>> #1 <https://github.com/sahlberg/libiscsi/issues/1>
>> 0x00005555557b751d in qemu_ram_addr_from_host_nofail (
>> ptr=0x3039303620008000) at /usr/src/qemu-kvm-1.2.0/exec.c:2835
>> ram_addr = 0
>> #2 <https://github.com/sahlberg/libiscsi/issues/2>
>> 0x00005555557b9177 in cpu_physical_memory_unmap (
>> buffer=0x3039303620008000, len=4986663671065686081, is_write=1,
>> access_len=1) at /usr/src/qemu-kvm-1.2.0/exec.c:3645
> buffer and len are ASCII junk.  It appears to be hex digits and it's not
> clear where they come from.
>
> It would be interesting to print *elem one stack frame up in #3
> virtqueue_fill() to show the iovecs and in/out counts.
I will collect that info for you.

Peter