Hi Jim, On Mon, Sep 18, 2017 at 02:06:13PM -0600, Jim Fehlig wrote:
Kernel 4.13 introduced finer-grained ptrace checks
When Apparmor is enabled and libvirtd is confined, attempting to start a domain fails
virsh start test error: Failed to start domain test error: internal error: child reported: Kernel does not provide mount namespace: Permission denied
The audit log contains
type=AVC msg=audit(1505466699.828:534): apparmor="DENIED" operation="ptrace" profile="/usr/sbin/libvirtd" pid=6621 comm="libvirtd" requested_mask="trace" denied_mask="trace" peer="/usr/sbin/libvirtd"
It seems access to /proc/<pid>/tasks already requires trace permissions.
It was also noticed that simply connecting to libvirtd (e.g. virsh list) resulted in the following entries in the audit log
type=AVC msg=audit(1505755799.975:65): apparmor="DENIED" operation="ptrace" profile="/usr/sbin/libvirtd" pid=1418 comm="libvirtd" requested_mask="trace" denied_mask="trace" peer="unconfined" type=AVC msg=audit(1505755799.976:66): apparmor="DENIED" operation="ptrace" profile="/usr/sbin/libvirtd" pid=1418 comm="libvirtd" requested_mask="trace" denied_mask="trace" peer="unconfined"
Both Apparmor denials can be fixed by adding ptrace rules to the libvirtd profile. The new rules only grant trace permission.
I'm seeing the same denials with 4.13 (4.13.1-1~exp1 (2017-09-11) in Debian) but the proposed profile change does not fix the vm start issue for me. I can't tell why atm, will have to look into this in more detail at the WE.
Resolves: https://bugzilla.suse.com/show_bug.cgi?id=1058847 Signed-off-by: Jim Fehlig <jfehlig@suse.com> ---
Even with debug enabled in libvirtd, I've had a hard time correlating a libvirtd action that results in the denied ptrace check seen in the audit log. I suspect it is related to accessing files in /proc as mentioned in the apparmor wiki
http://wiki.apparmor.net/index.php/TechnicalDo_Proc_and_ptrace
cc'ing some of the usual apparmor suspects for any words of wisdom.
examples/apparmor/usr.sbin.libvirtd | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/examples/apparmor/usr.sbin.libvirtd b/examples/apparmor/usr.sbin.libvirtd index acb59e071..ff84aa149 100644 --- a/examples/apparmor/usr.sbin.libvirtd +++ b/examples/apparmor/usr.sbin.libvirtd @@ -37,6 +37,10 @@ network packet dgram, network packet raw,
+ # Support finer-grained ptrace checks, which were enabled in kernel 4.13 + ptrace trace peer=/usr/sbin/libvirtd, + ptrace trace peer=unconfined, + # Very lenient profile for libvirtd since we want to first focus on confining # the guests. Guests will have a very restricted profile. / r, -- 2.14.1