On Wed, 6 Feb 2019 09:33:35 -0800 Nadav Amit <[email protected]> wrote:
> >> /* Copy ftrace_caller onto the trampoline memory */ > >> ret = probe_kernel_read(trampoline, (void *)start_offset, size); > >> @@ -818,6 +820,13 @@ create_trampoline(struct ftrace_ops *ops, unsigned > >> int *tramp_size) > >> /* ALLOC_TRAMP flags lets us know we created it */ > >> ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP; > >> > >> + /* > >> + * Module allocation needs to be completed by making the page > >> + * executable. The page is still writable, which is a security hazard, > >> + * but anyhow ftrace breaks W^X completely. > >> + */ > > > > Perhaps we should set the page to non writable after the page is > > updated? And set it to writable only when we need to update it. > > You remember that I sent you a patch that changed all these writes into > text_poke() and you said that I should defer it until this series is merged? > And I notice that it is set to RO after this call anyway. -- Steve
