issue with virtio_net in KVM guests with >= 3.14.5

[hagar-dunor]

Hi all,

The host qemu process crashes, at least exits silently (nothing in host dmesg or syslog) when the guest OS initialises the virtual network interface.
More precisely, I can modprobe virtio_net in the guest, but the host qemu exits if I attempt a "ifconfig eth0 up" in the guest.

I was upgrading my guests since 3.7.x and it always went fine, the issue appeared with 3.14.5. It's still there with 3.14.6.
Both host and guest OS are hardened gentoo. I tried with qemu stable (gentoo stable) 1.5.3 or 2.0.0-r1, same behavior. It doesn't seem to be related to the host kernel version. Also the issue in the guest doesn't happen if GRSEC is disabled in the guest kernel.

Hope it helps to look into it...
If there is anything I can do please ask, I have a test system I can mess with.

Cheers

[PaX Team]

does disabling KSTACKOVERFLOW in the guest kernel help?

[hagar-dunor]

yes it does ! the issue is gone with KSTACKOVERFLOW disabled

[jed]

I am experiencing the same issue with Arch Linux. Both host and guest are running Arch Linux with grsec kernels. In case this is helpful, the issue appeared in 3.14.4.201405252047 and persists through 3.14.6.201406101411. The version before, 3.14.4.201405141623, worked fine with guest virtio. Disabling KSTACKOVERFLOW in 3.14.5.201406051310 fixed the issue.

[strcat]

Here's another user with the same issue, along with some more details: https://bugs.archlinux.org/task/40627

[hagar-dunor]

On my systems it's solved in grsecurity-3.0-3.14.8-201406220132 (gentoo hardened-sources 3.14.8-r1) i.e. no issues anymore with KSTACKOVERFLOW enabled

Thanks guys for fixing it !