Re: [Qemu-devel] [PATCH] seccomp: add timerfd_create and timerfd_settime to the whitelist

[Felix Geyer <debfx@fobos.de>]

On 28.01.2014 14:00, Eduardo Otubo wrote:
> On 01/26/2014 10:21 AM, Felix Geyer wrote:
>> libusb calls timerfd_create() and timerfd_settime() when it's built with
>> timerfd support.
>>
>> Command to reproduce:
>>
>> qemu -sandbox on -monitor stdio -device piix3-usb-uhci,id=usb
>>       -device usb-host,hostbus=1,hostaddr=3,id=hostdev0
>>
>> Log messages:
>>
>> audit(1390730418.924:135): auid=4294967295 uid=121 gid=103 ses=4294967295
>>                             pid=5232 comm="qemu-system-x86" sig=31 syscall=283
>>                             compat=0 ip=0x7f2b0f4e96a7 code=0x0
>> audit(1390733100.580:142): auid=4294967295 uid=121 gid=103 ses=4294967295
>>                             pid=16909 comm="qemu-system-x86" sig=31 syscall=286
>>                             compat=0 ip=0x7f03513a06da code=0x0
>>
>> Signed-off-by: Felix Geyer <debfx@fobos.de>
>> ---
>>   qemu-seccomp.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/qemu-seccomp.c b/qemu-seccomp.c
>> index caa926e..2705468 100644
>> --- a/qemu-seccomp.c
>> +++ b/qemu-seccomp.c
>> @@ -225,7 +225,9 @@ static const struct QemuSeccompSyscall seccomp_whitelist[] = {
>>       { SCMP_SYS(fchmod), 240 },
>>       { SCMP_SYS(shmget), 240 },
>>       { SCMP_SYS(shmat), 240 },
>> -    { SCMP_SYS(shmdt), 240 }
>> +    { SCMP_SYS(shmdt), 240 },
>> +    { SCMP_SYS(timerfd_create), 240 },
>> +    { SCMP_SYS(timerfd_settime), 240 }
>
> Did you deliberately set the priority to 240? Or did you run any sort of benchmark (strace) to
> find this value?
>
> Regards,

Not really, sorry.

I've now done a benchmark on x86_64, copying a few hundred MB from a USB drive:

    calls  syscall
 --------- ----------------
   5303600 write
   2240554 read
   2167030 ppoll
   2134828 ioctl
    704023 timerfd_settime
    689105 poll
     83122 futex
       803 writev
       476 rt_sigprocmask
       287 recvmsg
       178 brk

timerfd_create is basically only called once so it can have the lowest priority.
timerfd_settime should probably have priority around 242.

Regards,
Felix