On Mon, Mar 09, 2020 at 09:49:31AM -0700, Guenter Roeck wrote: > 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 ? I thought Arnd sent a patch to fix it and it got picked up? -- Kees Cook
