Comment 3 for bug 1411294

fix uploaded.
just for some more information, can fairly easily reproduce this bug using a cloud image:

img_url="http://cloud-images.ubuntu.com/daily/server/vivid/current/vivid-server-cloudimg-amd64-disk1.img"
img_dl="${img_url##*/}"
wget -O "$img_dl" "$img_url"
qemu-img convert -O qcow2 "$img_dl" "disk.img.dist"
qemu-img create -f qcow2 -b disk.img.dist disk.img

# pull out kernel/initramfs
sudo mount-image-callback disk.img --read-only -- \
   sh -xc 'cp $MOUNTPOINT/boot/vmlinu?-* kernel &&
           cp $MOUNTPOINT/boot/initrd.* initrd &&
           chmod ugo+r kernel initrd'

# boot qemu, should boot to bash prompt, currently on vivid (3.18 + 0.25ubuntu1) will kernel panic
qemu-system-x86_64 -enable-kvm -m 1024 \
   -drive if=virtio,file=disk.img \
   -kernel kernel -initrd initrd \
   -append "root=LABEL=cloudimg-rootfs overlayroot=tmpfs:debug=1 console=ttyS0 init=/bin/bash" \
   -nographic -echr 0x5

# patchin a new deb
sudo mount-image-callback disk.img -- \
   sh -exc '
     deb=$1; shift;
     cp $deb $MOUNTPOINT/tmp/fix.deb
     chroot $MOUNTPOINT dpkg -i /tmp/fix.deb
     rm $MOUNTPOINT/tmp/fix.deb' -- overlayroot_0.26ubuntu1_all.deb

# then re-copy out the kernel and boot again to see fix.