On Wed, Apr 24, 2019 at 11:29:25AM -0700, Eric Dumazet wrote: > On Wed, Apr 24, 2019 at 11:21 AM Guillaume Nault <gna...@redhat.com> wrote: > > > > > And then, we'd need to make sure that ->sk_user_data is in sync with > > the encap_rcv() callback (or whatever actually uses the data pointed > > to). Otherwise a module could treat ->sk_user_data as a struct foo > > pointer while it actually points to a struct bar. > > > > For example, a quick look at net/sunrpc/svcsock.c seems to indicate > > that svc_addsock() would accept any (unconnected) UDP socket and pass > > it to svc_addsock(), which in turn would override ->sk_user_data with > > a struct svc_sock pointer. If the socket was previously set up by L2TP, > > then we'd end up with ->sk_user_data pointing to a svc_sock structure, > > but ->encap_rcv still pointing to l2tp_udp_encap_recv(). That's going > > to give unexpected results when l2tp_udp_encap_recv() will dereference > > ->sk_user_data to access (what it believes to be) its tunnel structure. > > A full audit is needed, and I have started it. If you want to help > just send a patch ;) > > I have looked at this l2tp code only after fixing another issue in > RXRPC, and would have > looked later at SUNRPC.
Hum, sorry, I didn't realise that. I'm really interested in the solutions you can come up with.
