On Sat, Feb 18, 2023 at 01:14:05PM -0800, Rick Edgecombe wrote: > The x86 Control-flow Enforcement Technology (CET) feature includes a new > type of memory called shadow stack. This shadow stack memory has some > unusual properties, which requires some core mm changes to function > properly. > > One of these unusual properties is that shadow stack memory is writable, > but only in limited ways. These limits are applied via a specific PTE > bit combination. Nevertheless, the memory is writable, and core mm code > will need to apply the writable permissions in the typical paths that > call pte_mkwrite(). > > In addition to VM_WRITE, the shadow stack VMA's will have a flag denoting > that they are special shadow stack flavor of writable memory. So make > pte_mkwrite() take a VMA, so that the x86 implementation of it can know to > create regular writable memory or shadow stack memory. > > Apply the same changes for pmd_mkwrite() and huge_pte_mkwrite(). > > No functional change. > > Cc: linux-doc@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > Cc: linux-alpha@xxxxxxxxxxxxxxx > Cc: linux-snps-arc@xxxxxxxxxxxxxxxxxxx > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Cc: linux-csky@xxxxxxxxxxxxxxx > Cc: linux-hexagon@xxxxxxxxxxxxxxx > Cc: linux-ia64@xxxxxxxxxxxxxxx > Cc: loongarch@xxxxxxxxxxxxxxx > Cc: linux-m68k@xxxxxxxxxxxxxxxxxxxx > Cc: Michal Simek <monstr@xxxxxxxxx> > Cc: Dinh Nguyen <dinguyen@xxxxxxxxxx> > Cc: linux-mips@xxxxxxxxxxxxxxx > Cc: openrisc@xxxxxxxxxxxxxxxxxxxx > Cc: linux-parisc@xxxxxxxxxxxxxxx > Cc: linuxppc-dev@xxxxxxxxxxxxxxxx > Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx > Cc: linux-s390@xxxxxxxxxxxxxxx > Cc: linux-sh@xxxxxxxxxxxxxxx > Cc: sparclinux@xxxxxxxxxxxxxxx > Cc: linux-um@xxxxxxxxxxxxxxxxxxx > Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx > Cc: linux-arch@xxxxxxxxxxxxxxx > Cc: linux-mm@xxxxxxxxx > Tested-by: Pengfei Xu <pengfei.xu@xxxxxxxxx> > Suggested-by: David Hildenbrand <david@xxxxxxxxxx> > Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> I'm not an arch maintainer, but it looks like a correct tree-wide refactor. Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook
