[libvirt] [PATCH] apparmor: allow qemu abstraction to read /proc/pid/cmdline

intrigeri intrigeri+libvirt at boum.org
Fri Dec 1 09:53:44 UTC 2017


Michal Privoznik:
> On 11/30/2017 06:43 PM, Jim Fehlig wrote:
>> I must admit it is not clear to me why
>> /proc/<libvirtd-pid>/cmdline is read on domain shutdown.

> It's result of these qemu patches:

> fbe7e3327a8cfa1b08664c2cda7a0a341cf0530a
> 7dc9ae4339faa97e89daadb2e1098147ab4aadc8

> Whenever qemu receives a signal it reports PID that sent it.

Thanks a lot for investigating!

>>  examples/apparmor/libvirt-qemu | 1 +
>>  1 file changed, 1 insertion(+)
>> diff --git a/examples/apparmor/libvirt-qemu b/examples/apparmor/libvirt-qemu
>> index 73bdbae87..3d9eed9ec 100644
>> --- a/examples/apparmor/libvirt-qemu
>> +++ b/examples/apparmor/libvirt-qemu
>> @@ -25,6 +25,7 @@
>>    /dev/ptmx rw,
>>    /dev/kqemu rw,
>>    @{PROC}/*/status r,
>> +  @{PROC}/@{pid}/cmdline r,
>>    # Per man(5) proc, the kernel enforces that a thread may
>>    # only modify its comm value or those in its thread group.
>>    owner @{PROC}/@{pid}/task/@{tid}/comm rw,

> ACK and safe for the freeze.


(I've seen this denial for a while but did not notice any problem it
would cause, so I was wondering if we should allow this operation or
just ignore the denial & silence the logs. Now that we understand what
it is about, I agree we should allow it. Denying this access would
make it harder to debug issues in the future e.g. if QEMU ever starts
needing it for other, more critical reasons.)


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