On Fri, Mar 9, 2018 at 12:57 AM, Alexei Starovoitov <a...@fb.com> wrote: > On 3/8/18 4:24 PM, Kees Cook wrote: >> >> As Andy asked earlier, why not DYN too to catch PIE executables? Seems >> like forcing the userspace helper to be non-PIE would defeat some of >> the userspace defenses in use in most distros. > > > because we don't add features without concrete users.
I disagree here. If you're going to add a magic trick that triggers an execve(), then I think you should either support *both* standard, widely-used types of ELF programs or you should give a compelling use case that works for ET_EXEC but not for ET_DYN. Keep in mind that many distros have a very strong preference for ET_DYN. Or you could argue that ET_DYN requires tooling changes, but I think it's awkward to ask the tooling to change in advance of the kernel being willing to actually invoke the thing. I'm not actually convinced that any tooling changes would be needed, though.
