On Sat, May 30, 2020 at 4:43 AM Kees Cook <[email protected]> wrote: > I mean, yes, that's certainly better, but it just seems a shame that > everyone has to do the get_unused/put_unused dance just because of how > SCM_RIGHTS does this weird put_user() in the middle. > > Can anyone clarify the expected failure mode from SCM_RIGHTS? Can we > move the put_user() after instead?
Honestly, I think trying to remove file descriptors and such after -EFAULT is a waste of time. If userspace runs into -EFAULT, userspace is beyond saving and can't really do much other than exit immediately. There are a bunch of places that will change state and then throw -EFAULT at the end if userspace supplied an invalid address, because trying to hold locks across userspace accesses just in case userspace supplied a bogus address is kinda silly (and often borderline impossible). You can actually see that even scm_detach_fds() currently just silently swallows errors if writing some header fields fails at the end.
