Re: [PATCH net-next v3 02/10] udp/ipv6: move pending section of udpv6_sendmsg

[Pavel Begunkov]

On 5/16/22 14:11, Paolo Abeni wrote:
> On Fri, 2022-05-13 at 16:26 +0100, Pavel Begunkov wrote:
> > Move up->pending section of udpv6_sendmsg() to the beginning of the
> > function. Even though it require some code duplication for sin6 parsing,
> > it clearly localises the pending handling in one place, removes an extra
> > if and more importantly will prepare the code for further patches.
> >
> > Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> > ---
> >   net/ipv6/udp.c | 70 ++++++++++++++++++++++++++++++--------------------
> >   1 file changed, 42 insertions(+), 28 deletions(-)
> >
> > diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> > index 11d44ed46953..85bff1252f5c 100644
> > --- a/net/ipv6/udp.c
> > +++ b/net/ipv6/udp.c
> > @@ -1318,6 +1318,46 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
> >   	ipc6.sockc.tsflags = sk->sk_tsflags;
> >   	ipc6.sockc.mark = sk->sk_mark;
> >   
> > +	/* Rough check on arithmetic overflow,
> > +	   better check is made in ip6_append_data().
> > +	   */
> > +	if (unlikely(len > INT_MAX - sizeof(struct udphdr)))
> > +		return -EMSGSIZE;
> > +
> > +	getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;
> > +
> > +	/* There are pending frames. */
> > +	if (up->pending) {
> > +		if (up->pending == AF_INET)
> > +			return udp_sendmsg(sk, msg, len);
> > +
> > +		/* Do a quick destination sanity check before corking. */
> > +		if (sin6) {
> > +			if (msg->msg_namelen < offsetof(struct sockaddr, sa_data))
> > +				return -EINVAL;
> > +			if (sin6->sin6_family == AF_INET6) {
> > +				if (msg->msg_namelen < SIN6_LEN_RFC2133)
> > +					return -EINVAL;
> > +				if (ipv6_addr_any(&sin6->sin6_addr) &&
> > +				    ipv6_addr_v4mapped(&np->saddr))
> > +					return -EINVAL;
>
> It looks like 'any' destination with ipv4 mapped source is now
> rejected, while the existing code accept it.

It should be up->pending == AF_INET6 to get there, and previously it'd
fall into udp_sendmsg() and fail

if (unlikely(up->pending != AF_INET))
        return -EINVAL;

I don't see it anyhow rejecting cases that were working before.
Can you elaborate a bit?

--
Pavel Begunkov