On 06/13/2015 06:02 PM, Tycho Andersen wrote: > This patch is the first step in enabling checkpoint/restore of processes > with seccomp enabled. > > One of the things CRIU does while dumping tasks is inject code into them > via ptrace to collect information that is only available to the process > itself. However, if we are in a seccomp mode where these processes are > prohibited from making these syscalls, then what CRIU does kills the task. > > This patch adds a new ptrace option, PTRACE_O_SUSPEND_SECCOMP, that enables > a task from the init user namespace which has CAP_SYS_ADMIN and no seccomp > filters to disable (and re-enable) seccomp filters for another task so that > they can be successfully dumped (and restored). We restrict the set of > processes that can disable seccomp through ptrace because although today > ptrace can be used to bypass seccomp, there is some discussion of closing > this loophole in the future and we would like this patch to not depend on > that behavior and be future proofed for when it is removed. > > Note that seccomp can be suspended before any filters are actually > installed; this behavior is useful on criu restore, so that we can suspend > seccomp, restore the filters, unmap our restore code from the restored > process' address space, and then resume the task by detaching and have the > filters resumed as well. > > v2 changes: > > * require that the tracer have no seccomp filters installed > * drop TIF_NOTSC manipulation from the patch > * change from ptrace command to a ptrace option and use this ptrace option > as the flag to check. This means that as soon as the tracer > detaches/dies, seccomp is re-enabled and as a corrollary that one can not > disable seccomp across PTRACE_ATTACHs. > > v3 changes: > > * get rid of various #ifdefs everywhere > * report more sensible errors when PTRACE_O_SUSPEND_SECCOMP is incorrectly > used > > v4 changes: > > * get rid of may_suspend_seccomp() in favor of a capable() check in ptrace > directly > > v5 changes: > > * check that seccomp is not enabled (or suspended) on the tracer > > Signed-off-by: Tycho Andersen <tycho.andersen@xxxxxxxxxxxxx> > CC: Kees Cook <keescook@xxxxxxxxxxxx> > CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > CC: Will Drewry <wad@xxxxxxxxxxxx> > CC: Roland McGrath <roland@xxxxxxxxxxxxx> > CC: Oleg Nesterov <oleg@xxxxxxxxxx> > CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > CC: Serge E. Hallyn <serge.hallyn@xxxxxxxxxx> Acked-by: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
