Re: QEMU malfunctioning if built with FORTIFY_SOURCE=3

[Claudio Fontana]

On 5/27/22 18:55, Dario Faggioli wrote:
> Hello Everyone!
> 
> So, I'm not sure how much this would be interesting, but I thought
> about reporting it anyways, then let's see.
> 
> A few days ago we started to build openSUSE_Tumbleweed packages with
> -D_FORTIFY_SOURCES=3 by default (it was =2 before, and it's back to =2
> again now, at least for QEMU :-/).
> 
> It seemed fine, but then we discovered that a QEMU built that way, does
> not work properly. In fact, it crashes pretty early displaying a
> message like this: "*** buffer overflow detected ***"

Hi Dario and all,

I just sent a fix to the list,

with the Subject

"[PATCH] pci: fix overflow in printf string formatting"

That should fix the issue,

Thanks,

Claudio

> 
> I've had a look around, and did not find anything about previous
> attempts of doing that, or things to be aware of, in general, if doing
> it.
> 
> Now, for now, I don't have many other info myself either. Just some
> terminal logs from a few users, and from our automated testing system,
> i.e., like this:
> 
> $ sudo virsh start VM1
> error: Failed to start domain 'VM1'
> error: internal error: qemu unexpectedly closed the monitor: qxl_send_events: 
> spice-server bug: guest stopped, ignoring
> *** buffer overflow detected ***: terminated
> 
> Or this:
> 
> error: Failed to start domain 'vm-swtpm-legacy'
> error: internal error: qemu unexpectedly closed the monitor: 
> 2022-05-25T16:30:05.738186Z qemu-system-x86_64: -accel kvm: warning: Number 
> of SMP cpus requested (2) exceeds the recommended cpus supported by KVM (1)
> 2022-05-25T16:30:05.738259Z qemu-system-x86_64: -accel kvm: warning: Number 
> of hotpluggable cpus requested (2) exceeds the recommended cpus supported by 
> KVM (1)
> 2022-05-25T16:30:05.742354Z qemu-system-x86_64: warning: host doesn't support 
> requested feature: MSR(48FH).vmx-exit-load-perf-global-ctrl [bit 12]
> 2022-05-25T16:30:05.742369Z qemu-system-x86_64: warning: host doesn't support 
> requested feature: MSR(490H).vmx-entry-load-perf-global-ctrl [bit 13]
> 2022-05-25T16:30:05.743989Z qemu-system-x86_64: warning: host doesn't support 
> requested feature: MSR(48FH).vmx-exit-load-perf-global-ctrl [bit 12]
> 2022-05-25T16:30:05.744050Z qemu-system-x86_64: warning: host doesn't support 
> requested feature: MSR(490H).vmx-entry-load-perf-global-ctrl [bit 13]
> *** buffer overflow detected ***: terminated
> 
> Or this:
> https://openqa.opensuse.org/tests/2375666#step/usr_sbin_dnsmasq/47
> https://xenbits.xen.org/people/dariof/download.png (also here, in case
> the image disappears from OpenQA)
> 
> I am planning to try to investigate this more, but not right away. And
> I can't even tell for sure when I'll have time for it. So, this is just
> for letting people know that this has been (quickly) attempted, and
> that it currently does not work, in case it's interesting for anyone
> else.
> 
> Of course, in case it's the other way around, i.e., someone already has
> more info on the subject that I've not been able to find, feel free to
> ping me. :-)
> 
> Thanks and Regards