On Thu, Jan 19, 2017 at 10:56:46AM +0000, Mark Rutland wrote: > > +config HARDENED_PAGE_MAPPINGS > > + bool "Mark kernel mappings with stricter permissions (RO/W^X)" > > + default y > > + depends on ARCH_HAS_HARDENED_MAPPINGS > > + help > > + If this is set, kernel text and rodata memory will be made read-only, > > + and non-text memory will be made non-executable. This provides > > + protection against certain security attacks (e.g. executing the heap > > + or modifying text). > > + > > + Unless your system has known restrictions or performance issues, it > > + is recommended to say Y here. > > It's somewhat unfortunate that this means the feature is no longer > mandatory on arm64 (and s390+x86). We have a boot-time switch to turn > the protections off, so I was hoping we could make this mandatory on all > architectures with support. > > It would be good to see if we could make this mandatory for arm and > parisc, or if it really needs to be optional for either of those. Looks like the config option is a no-op on parisc just like it is on s390. Irrelavant of the config option at least on s390 the page tables for kernel text and rodata will be read-only anyway. This works since ages and I don't see a reason why this should be changed. Also trying to disable this with the "rodata=" command line option does not work at least on s390, and I guess this is true for parisc as well. The only thing implemented with CONFIG_DEBUG_RODATA on both architectures is to emit a message that states memory has been protected (mark_rodata_ro). This just avoids a wrong "Kernel memory protection disabled." message. So yes, I'd really like to keep this option mandatory. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
