On Sat, Feb 06, 2021 at 03:28:28PM -0800, Jakub Kicinski wrote: > On Sat, 6 Feb 2021 12:36:48 -0800 Arjun Roy wrote: > > From: Arjun Roy <arjun...@google.com> > > > > Explicitly define reserved field and require it to be 0-valued. > > > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > > index e1a17c6b473c..c8469c579ed8 100644 > > --- a/net/ipv4/tcp.c > > +++ b/net/ipv4/tcp.c > > @@ -4159,6 +4159,8 @@ static int do_tcp_getsockopt(struct sock *sk, int > > level, > > } > > if (copy_from_user(&zc, optval, len)) > > return -EFAULT; > > + if (zc.reserved) > > + return -EINVAL; > > lock_sock(sk); > > err = tcp_zerocopy_receive(sk, &zc, &tss); > > release_sock(sk); > > I was expecting we'd also throw in a check_zeroed_user(). > Either we can check if the buffer is zeroed all the way, > or we can't and we shouldn't validate reserved either > > check_zeroed_user(optval + offsetof(reserved), > len - offsetof(reserved)) > ?
There is a check that len is not larger than zs and users can't give large buffer. I would say that is pretty safe to write "if (zc.reserved)". Thanks
