Hi, you all may know that Xenomai provides a bulk of very powerful interfaces to userspace real-time applications. But not everyone may have thought about the fact yet that these syscall extensions are accessible for *all* users in the system!
Well, real-time and security is a more complex topic, but we should at least restore the same level of security which Linux provides. For this purpose, the attached (and long-planned) patch adds basic access control to all Xenomai skin services by requiring CAP_SYS_NICE, i.e. the same capability that is also required to manipulate the normal Linux scheduling parameters. I would suggest to merge it, either as an option (with default=y), or unconditionally (it's just a tiny additional check in the syscall path). Jan
Index: ksrc/nucleus/shadow.c
===================================================================
--- ksrc/nucleus/shadow.c (revision 719)
+++ ksrc/nucleus/shadow.c (working copy)
@@ -1141,6 +1141,12 @@ static inline int do_hisyscall_event (un
if (!__xn_reg_mux_p(regs))
goto linux_syscall;
+ if (unlikely(!cap_raised(p->cap_effective, CAP_SYS_NICE)))
+ {
+ __xn_error_return(regs,-EPERM);
+ return RTHAL_EVENT_STOP;
+ }
+
muxid = __xn_mux_id(regs);
muxop = __xn_mux_op(regs);
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