On Thu, Dec 06, 2018 at 09:32:57AM +0100, Ard Biesheuvel wrote: > On ARM, we currently only change the value of the stack canary when > switching tasks if the kernel was built for UP. On SMP kernels, this > is impossible since the stack canary value is obtained via a global > symbol reference, which means > a) all running tasks on all CPUs must use the same value > b) we can only modify the value when no kernel stack frames are live > on any CPU, which is effectively never. > > So instead, use a GCC plugin to add a RTL pass that replaces each > reference to the address of the __stack_chk_guard symbol with an > expression that produces the address of the 'stack_canary' field > that is added to struct thread_info. This way, each task will use > its own randomized value. > > Cc: Russell King <linux@xxxxxxxxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Emese Revfy <re.emese@xxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Laura Abbott <labbott@xxxxxxxxxx> > Cc: kernel-hardening@xxxxxxxxxxxxxxxxxx > Acked-by: Nicolas Pitre <nico@xxxxxxxxxx> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> Since this patch is in the tree, cc-option no longer works on the arm architecture if CONFIG_STACKPROTECTOR_PER_TASK is enabled. Any idea how to fix that ? Thanks, Guenter
