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Description of problem:
When a USB sound device is assigned to or removed from a QEMU-KVM guest, an AVC denial occurs when alsactl tries to create a lock file under /var/lock.
Version-Release number of selected component (if applicable):
selinux-policy-3.7.19-292.el6.noarch
selinux-policy-targeted-3.7.19-292.el6.noarch
How reproducible:
Always.
Steps to Reproduce:
1. In virt-manager, click on "Add Hardware", select "USB Host Device" and an available USB sound device.
2. Click "Finish".
Actual results:
AVC denials either immediately if the guest is running, or when the guest is started.
type=AVC msg=audit(1464239503.474:168): avc: denied { write } for pid=6462 comm="alsactl" name="lock" dev="dm-1" ino=1310721 scontext=system_u:system_r:alsa_t:s0-s0:c0.c1023 tcontext=system_u:object_r:var_lock_t:s0 tclass=dir permissive=0
type=SYSCALL msg=audit(1464239503.474:168): arch=x86_64 syscall=open success=no exit=EACCES a0=4122a3 a1=c2 a2=1a4 a3=7fff7e7950a0 items=0 ppid=6325 pid=6462 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm=alsactl exe=/sbin/alsactl subj=system_u:system_r:alsa_t:s0-s0:c0.c1023 key=(null)
Expected results:
No AVC.
Additional info:
Problem is new following an update from CentOS 6.7 to 6.8.
The device is a 0d8c:013c C-Media Electronics USB PnP Sound Device, but I suspect the particular device does not matter. Similar AVC denials occur when removing the device from the guest or if the guest is shut down while the device is assigned.
Could you repeat the same scenario in permissive mode? Please collect SELinux denials which appear during the time:
# ausearch -m avc -m user_avc -i -ts today
Created attachment 1191317[details]
Results from ausearch -m avc -m user_avc -i -ts today
Results attached. Here is the local policy module that I use to stop the complaints:
module alsalock 1.0;
require {
type alsa_t;
type var_lock_t;
class dir { write add_name };
class file { create open };
}
#============= alsa_t ==============
#!!!! The source type 'alsa_t' can write to a 'dir' of the following types:
# alsa_var_lib_t, etc_t, alsa_etc_rw_t
allow alsa_t var_lock_t:dir { write add_name };
allow alsa_t var_lock_t:file { create open };
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHBA-2017-0627.html
Description of problem: When a USB sound device is assigned to or removed from a QEMU-KVM guest, an AVC denial occurs when alsactl tries to create a lock file under /var/lock. Version-Release number of selected component (if applicable): selinux-policy-3.7.19-292.el6.noarch selinux-policy-targeted-3.7.19-292.el6.noarch How reproducible: Always. Steps to Reproduce: 1. In virt-manager, click on "Add Hardware", select "USB Host Device" and an available USB sound device. 2. Click "Finish". Actual results: AVC denials either immediately if the guest is running, or when the guest is started. type=AVC msg=audit(1464239503.474:168): avc: denied { write } for pid=6462 comm="alsactl" name="lock" dev="dm-1" ino=1310721 scontext=system_u:system_r:alsa_t:s0-s0:c0.c1023 tcontext=system_u:object_r:var_lock_t:s0 tclass=dir permissive=0 type=SYSCALL msg=audit(1464239503.474:168): arch=x86_64 syscall=open success=no exit=EACCES a0=4122a3 a1=c2 a2=1a4 a3=7fff7e7950a0 items=0 ppid=6325 pid=6462 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm=alsactl exe=/sbin/alsactl subj=system_u:system_r:alsa_t:s0-s0:c0.c1023 key=(null) Expected results: No AVC. Additional info: Problem is new following an update from CentOS 6.7 to 6.8. The device is a 0d8c:013c C-Media Electronics USB PnP Sound Device, but I suspect the particular device does not matter. Similar AVC denials occur when removing the device from the guest or if the guest is shut down while the device is assigned.