On Wed, Nov 2, 2022 at 3:27 PM Alexander Potapenko <glider@xxxxxxxxxx> wrote: > > On Fri, Oct 28, 2022 at 6:14 PM Luck, Tony <tony.luck@xxxxxxxxx> wrote: > > > > >> + vfrom = kmap_local_page(from); > > >> + vto = kmap_local_page(to); > > >> + ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE); > > > > > > In copy_user_highpage(), kmsan_unpoison_memory(page_address(to), PAGE_SIZE) is done after the copy when > > > __HAVE_ARCH_COPY_USER_HIGHPAGE isn't defined. Do we need to do something similar here? But I'm not familiar > > > with kmsan, so I can easy be wrong. > > > > It looks like that kmsan_unpoison_memory() call was added recently, after I copied > > copy_user_highpage() to create copy_mc_user_highpage(). I'm not familiar with > > kmsan either. Adding Alexander to this thread since they added that code. > > > > Given that copy_mc_user_highpage() replaces one of the calls to > copy_user_highpage(), it sure makes sense to call > kmsan_unpoison_memory() here. > > KMSAN tracks the status (initialized/uninitialized) of the kernel > memory. Newly allocated memory is marked uninitialized, copying memory > preserves its status, and writing constants to that memory makes it > initialized. > Userspace memory does not have its status tracked by KMSAN, so when > values are copied from the userspace, KMSAN does nothing with their > status. > That's why every (successful) copy_from_user event should be followed > by kmsan_unpoison_memory(), which marks the corresponding kernel > buffer initialized - otherwise the status of that buffer may get > stale. > > > > Anyway, this patch looks good to me. Thanks. > > > > > > Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx> > > > > Thanks for the review. > > > > -Tony > > > > -- > Alexander Potapenko > Software Engineer > > Google Germany GmbH > Erika-Mann-Straße, 33 > 80636 München > > Geschäftsführer: Paul Manicle, Liana Sebastian > Registergericht und -nummer: Hamburg, HRB 86891 > Sitz der Gesellschaft: Hamburg -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
