seccomp: whitelist syscalls fallocate(), fadvise64(), inotify_init1() and inotify_add_watch()

fallocate() is needed for snapshotting. If it isn’t whitelisted

    $ qemu-img create -f qcow2 x.qcow 1G
    Formatting 'x.qcow', fmt=qcow2 size=1073741824 encryption=off cluster_size=65536 lazy_refcounts=off
    $ qemu-kvm -display none -monitor stdio -sandbox on x.qcow
    QEMU 2.1.50 monitor - type 'help' for more information
    (qemu) savevm foo
    (qemu) loadvm foo

will fail, as will subsequent savevm commands on the same image.

fadvise64(), inotify_init1(), inotify_add_watch() are needed by
the SDL display. Without the whitelist entries,

    qemu-kvm -sandbox on

fails immediately.

In my tests fadvise64() is called 50--51 times per VM run. That
number seems independent of the duration of the run. fallocate(),
inotify_init1(), inotify_add_watch() are called once each.
Accordingly, they are added to the whitelist at a very low
priority.
Signed-off-by: NPhilipp Gesang <philipp.gesang@intra2net.com>
Signed-off-by: NEduardo Otubo <eduardo.otubo@profitbricks.com>

qemu-seccomp.c

@@ -231,7 +231,11 @@ static const struct QemuSeccompSyscall seccomp_whitelist[] = {
     { SCMP_SYS(shmctl), 240 },
     { SCMP_SYS(mlock), 240 },
     { SCMP_SYS(munlock), 240 },
-    { SCMP_SYS(semctl), 240 }
+    { SCMP_SYS(semctl), 240 },
+    { SCMP_SYS(fallocate), 240 },
+    { SCMP_SYS(fadvise64), 240 },
+    { SCMP_SYS(inotify_init1), 240 },
+    { SCMP_SYS(inotify_add_watch), 240 }
 };
 
 int seccomp_start(void)