On Tue, 2018-06-19 at 13:47 -0700, Andy Lutomirski wrote: > > > > On Jun 19, 2018, at 1:12 PM, Kees Cook <keescook@xxxxxxxxxxxx> > > wrote: > > > > > > > > On Tue, Jun 19, 2018 at 10:20 AM, Andy Lutomirski <luto@amacapita > > > l.net> wrote: > > > > > > > > > > > On Jun 19, 2018, at 10:07 AM, Kees Cook <keescook@xxxxxxxxxxxx> > > > > wrote: > > > > > > > > Does it provide anything beyond what PR_DUMPABLE does? > > > What do you mean? > > I was just going by the name of it. I wasn't sure what "ptrace CET > > lock" meant, so I was trying to understand if it was another "you > > can't ptrace me" toggle, and if so, wouldn't it be redundant with > > PR_SET_DUMPABLE = 0, etc. > > > No, other way around. The valid CET states are on/unlocked, > off/unlocked, on/locked, off/locked. arch_prctl can freely the state > unless locked. ptrace can change it no matter what. The lock is to > prevent the existence of a gadget to disable CET (unless the gadget > involves ptrace, but I don’t think that’s a real concern). We have the arch_prctl now and only need to add ptrace lock/unlock. Back to the dlopen() "relaxed" mode. Would the following work? If the lib being loaded does not use setjmp/getcontext families (the loader knows?), then the loader leaves shstk on. Otherwise, if the system-wide setting is "relaxed", the loader turns off shstk and issues a warning. In addition, if (dlopen == relaxed), then cet is not locked in any time. The system-wide setting (somewhere in /etc?) can be: dlopen=force|relaxed /* controls dlopen of non-cet libs */ exec=force|relaxed /* controls exec of non-cet apps */ -- Yu-cheng
