On Thu, Jul 06, 2017 at 09:29:27PM +0100, Al Viro wrote: > On Thu, Jul 06, 2017 at 09:18:26PM +0100, Al Viro wrote: > > On Thu, Jul 06, 2017 at 12:45:36PM -0700, Kees Cook wrote: > > > > > > + if (unlikely(!check_copy_size(addr, bytes, false))) > > > + return false; > > > + else > > > + return _copy_from_iter_full(addr, bytes, i); > > > > > > Can these be rewritten to avoid the double-negative? > > > > Matter of taste - I've no strong preferences here. > > > > > + might_fault(); > > > > > > Should this be might_sleep()? Just from reading the patch it looked > > > like you were adding might_sleep()s in the other cases. > > > > D'oh - shouldn't have written that pull request message before the > > first cup of coffee... might_sleep() it is, of course. > > Hrm... Said that, might_sleep() doesn't check one thing might_fault() > does - the > #if defined(CONFIG_DEBUG_ATOMIC_SLEEP) > if (current->mm) > might_lock_read(¤t->mm->mmap_sem); > #endif > thing. Let me think a bit... FWIW, * with iovec-backed, any of those primitives under pagefault_disable() is seriously wrong. To the point where we probably want to complain when called that way. That, of course, needs to be checked at the outermost level - the primitives might do pagefault_disable() internally; that's fine. Outside caller doing that under pagefault_disable() isn't. * uaccess_kernel() (== set_fs(KERNEL_DS)) has nothing to do with it. If anything, we should not do copyin/copyout on iovec-backed ones with that present. * telling lockdep that we might end up grabbing ->mm->mmap_sem, OTOH, is the right thing to do. In addition to might_sleep(). Linus, could you hold that one back until tomorrow? I want to tweak the last commit in there a bit, but I want to give it a local beating first...
