Re: [libvirt] libvirt? qemu change that mmaps ELF files breaks libvirt svirt handling for os.kernel
On 04.10.19 14:13, Paolo Bonzini wrote:
On 04/10/19 14:03, Christian Borntraeger wrote:
> Stefano, Paolo,
>
> I have an interesting fail in QEMU
>
> 2019-10-04T12:00:32.675188Z qemu-system-s390x: GLib: g_mapped_file_unref: assertion
'file != NULL' failed
> that bisected to
> commit 816b9fe450220e19acb91a0ce4a8ade7000648d1 (refs/bisect/bad)
> elf-ops.h: Map into memory the ELF to load
>
> strace tells that I can read the ELF file, but not mmap
> strace:
> 214365 openat(AT_FDCWD, "/var/lib/libvirt/images/test_cpu_timer.elf",
O_RDONLY) = 36
> 214365 read(46, "\177ELF\2\2\1\0\0\0\0\0\0\0\0\0", 16) = 16
> 214365 lseek(46, 0, SEEK_SET) = 0
> [...]
> 214365 fstat(46, {st_mode=S_IFREG|0755, st_size=168176, ...}) = 0
> 214365 mmap(NULL, 168176, PROT_READ|PROT_WRITE, MAP_PRIVATE, 46, 0) = -1 EACCES
(Permission denied)
>
> So reading from /var/lib/libvirt/images/test_cpu_timer.elf does work, mmaping does
not.
> setenforce 0 makes the problem go away.
>
> This might be more of an issue in libvirt, setting the svirt context too
> restrictive, but I am not too deep into the svirt part of libvirt.
> Reverting the qemu commit makes the problem go away.
Yes, the policy is too restrictive in my opinion.
Can you include the output of "audit2allow" and/or "audit2allow -R"?
Thanks,
Paolo
require {
type unconfined_t;
type virt_content_t;
type svirt_t;
type systemd_tmpfiles_t;
type user_home_t;
type NetworkManager_t;
class file { entrypoint execute ioctl lock map open read write };
class bpf prog_run;
}
#============= svirt_t ==============
allow svirt_t user_home_t:file { entrypoint execute ioctl lock open read write };
#!!!! This avc can be allowed using the boolean 'domain_can_mmap_files'
allow svirt_t virt_content_t:file map;
corecmd_bin_entry_type(svirt_t)
userdom_manage_user_home_content_dirs(svirt_t)
userdom_map_user_home_files(svirt_t)
virt_rw_svirt_image(svirt_t)
#============= systemd_tmpfiles_t ==============
kernel_read_usermodehelper_state(systemd_tmpfiles_t)
#============= unconfined_t ==============
allow unconfined_t NetworkManager_t:bpf prog_run;