Unexplicable permission error when trying to read a qemu firmware file
Hi I want to create a CoreOS VM following the steps mentioned at https://docs.fedoraproject.org/en-US/fedora-coreos/getting-started, using a Debian 11 (bullseye) system. I am thus creating a VM with the following virt-install command: virt-install --connect="qemu:///system" --name=coreos \ --vcpus=2 --memory=2048 \ --os-variant=fedora29 --import --graphics=none \ --disk="size=10,backing_store=$PWD/fedora-coreos-33.20201201.3.0-qemu.x86_64.qcow2" \ --qemu-commandline="-fw_cfg name=opt/com.coreos/config,file=/tmp/example.ign" which spits some warnings and this mysterious error 2020-12-29T16:52:03.858938Z qemu-system-x86_64: warning: host doesn't support requested feature: MSR(48FH).vmx-exit-load-perf-global-ctrl [bit 12] 2020-12-29T16:52:03.858941Z qemu-system-x86_64: warning: host doesn't support requested feature: MSR(490H).vmx-entry-load-perf-global-ctrl [bit 13] 2020-12-29T16:52:03.864778Z qemu-system-x86_64: -fw_cfg name=opt/com.coreos/config,file=/tmp/example.ign: can't load /tmp/example.ign: Failed to open file “/tmp/example.ign”: Permission denied the file /tmp/example.ign is perfectly world readable, -rw-rw-rw- 1 manu manu 1130 Dec 29 17:23 /tmp/example.ign so I am puzzled at what could cause this permission error. on a RHEL8 system, I had the same error, and was able to fix by setting a security context on the firmware file: sudo semanage fcontext --add --type virt_content_t /tmp/example.ign restorecon /tmp/example.ign now this Debian system does not selinux installed at all. ls -dZ / ? / I could also read the qemu firmware file when using the qemu:///session connection any pointers where to look for ? Emmanuel
On 12/29/20 6:09 PM, Emmanuel Kasper wrote:
Hi
I want to create a CoreOS VM following the steps mentioned at https://docs.fedoraproject.org/en-US/fedora-coreos/getting-started, using a Debian 11 (bullseye) system. I am thus creating a VM with the following virt-install command:
virt-install --connect="qemu:///system" --name=coreos \ --vcpus=2 --memory=2048 \ --os-variant=fedora29 --import --graphics=none \
--disk="size=10,backing_store=$PWD/fedora-coreos-33.20201201.3.0-qemu.x86_64.qcow2" \ --qemu-commandline="-fw_cfg name=opt/com.coreos/config,file=/tmp/example.ign"
1: this ^^
which spits some warnings and this mysterious error
2020-12-29T16:52:03.858938Z qemu-system-x86_64: warning: host doesn't support requested feature: MSR(48FH).vmx-exit-load-perf-global-ctrl [bit 12] 2020-12-29T16:52:03.858941Z qemu-system-x86_64: warning: host doesn't support requested feature: MSR(490H).vmx-entry-load-perf-global-ctrl [bit 13]
I don't know what are these, sorry.
2020-12-29T16:52:03.864778Z qemu-system-x86_64: -fw_cfg name=opt/com.coreos/config,file=/tmp/example.ign: can't load /tmp/example.ign: Failed to open file “/tmp/example.ign”: Permission denied
But this is expected.
the file /tmp/example.ign is perfectly world readable, -rw-rw-rw- 1 manu manu 1130 Dec 29 17:23 /tmp/example.ign
This doesn't matter. It's SELinux what's giving you the error (as you've found out). The problem here is [1]. If you bypass libvirt and put something right onto qemu's command line then libvirt blindly puts it there. No checks, no DAC/SELinux relabel, nothing. But I've implemented support for ignition files here: https://gitlab.com/libvirt/libvirt/-/commit/3dda889a4426bb3555b1d8861d8314f8... So what you need instead is: <sysinfo type='fwcfg'> <entry name='opt/com.coreos/config' file='/tmp/example.ign'/> </sysinfo> This will make libvirt set correct labels and everything. I'm not sure whether virt-install supports that though, sorry. Michal
participants (2)
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Emmanuel Kasper -
Michal Privoznik