On Fri, Feb 10, 2017 at 4:01 PM, Tyler Hicks <tyhi...@canonical.com> wrote: > On 02/07/2017 06:33 PM, Kees Cook wrote: >> This adds to UAPI, so it'd be good to think for a moment about how >> this would work on older kernels: right now, if someone tried to use >> this RET_LOG on an old kernel, it'll get treated like RET_KILL. Is >> this sane? > > It is not sane for userspace code to blindly attempt to use a new > feature on an old kernel. One of the main motivations of the > actions_avail sysctl is to allow userspace to be smart about what the > current kernel supports.
Yeah, agreed. I mean, userspace could also build a little test program, toss in RET_LOG, run it and see if it get SIGSYS. But that's so much more pain that checking in /proc. > I'll be adding logic (requested by Paul) to libseccomp that checks this > sysctl when SECOMP_RET_LOG is attempted to be used. Programs that don't > use libseccomp will have to do something similar. Excellent, I had been meaning to ask if you'd chatted with Paul at all, since this is an API addition for libseccomp. Speaking of which, can you CC linux-api@ on the next version too? -Kees -- Kees Cook Pixel Security
