* Nicholas Miell <nmiell@xxxxxxxxxxx> wrote: > On Wed, 2009-05-06 at 15:21 -0700, Markus Gutschke (顧孟勤) wrote: > > On Wed, May 6, 2009 at 15:13, Ingo Molnar <mingo@xxxxxxx> wrote: > > > doing a (per arch) bitmap of harmless syscalls and replacing the > > > mode1_syscalls[] check with that in kernel/seccomp.c would be a > > > pretty reasonable extension. (.config controllable perhaps, for > > > old-style-seccomp) > > > > > > It would probably be faster than the current loop over > > > mode1_syscalls[] as well. > > > > This would be a great option to improve performance of our sandbox. I > > can detect the availability of the new kernel API dynamically, and > > then not intercept the bulk of the system calls. This would allow the > > sandbox to work both with existing and with newer kernels. > > > > We'll post a kernel patch for discussion in the next few days, > > > > I suspect the correct thing to do would be to leave seccomp mode 1 > alone and introduce a mode 2 with a less restricted set of system > calls -- the interface was designed to be extended in this way, > after all. Yes, that is what i alluded to above via the '.config controllable' aspect. Mode 2 could be implemented like this: extend prctl_set_seccomp() with a bitmap pointer, and copy it to a per task seccomp context structure. a bitmap for 300 syscalls takes only about 40 bytes. Please take care to implement nesting properly: if a seccomp context does a seccomp call (which mode 2 could allow), then the resulting bitmap should be the logical-AND of the parent and child bitmaps. There's no reason why seccomp couldnt be used in hiearachy of sandboxes, in a gradually less permissive fashion. Ingo
