On Thu, Apr 01, 2021 at 04:23:46PM -0700, Kees Cook wrote: > Allow for a randomized stack offset on a per-syscall basis, with roughly > 5 bits of entropy. (And include AAPCS rationale AAPCS thanks to Mark > Rutland.) > > In order to avoid unconditional stack canaries on syscall entry (due to > the use of alloca()), also disable stack protector to avoid triggering > needless checks and slowing down the entry path. As there is no general > way to control stack protector coverage with a function attribute[1], > this must be disabled at the compilation unit level. This isn't a problem > here, though, since stack protector was not triggered before: examining > the resulting syscall.o, there are no changes in canary coverage (none > before, none now). > > [1] a working __attribute__((no_stack_protector)) has been added to GCC > and Clang but has not been released in any version yet: > https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=346b302d09c1e6db56d9fe69048acb32fbb97845 > https://reviews.llvm.org/rG4fbf84c1732fca596ad1d6e96015e19760eb8a9b > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > arch/arm64/Kconfig | 1 + > arch/arm64/kernel/Makefile | 5 +++++ > arch/arm64/kernel/syscall.c | 16 ++++++++++++++++ > 3 files changed, 22 insertions(+) Acked-by: Will Deacon <will@xxxxxxxxxx> Will
