On Wed, 2023-05-31 at 10:48 +0300, Dan Carpenter wrote:
> On Wed, May 31, 2023 at 08:27:43AM +1000, NeilBrown wrote:
> > On Mon, 29 May 2023, Dan Carpenter wrote:
> > > The bug here is that you cannot rely on getting the same socket
> > > from multiple calls to fget() because userspace can influence
> > > that. This is a kind of double fetch bug.
> > >
> > > The fix is to delete the svc_alien_sock() function and insted do
> > > the checking inside the svc_addsock() function.
> >
> > Hi,
> > I definitely agree with the change to pass the 'net' into
> > svc_addsock(), and check the the fd has the correct net.
> >
> > I'm not sure I agree with the removal of the svc_alien_sock() test. It
> > is best to perform sanity tests before allocation things, and
> > nfsd_create_serv() can create a new 'serv' - though most often it just
> > incs the refcount.
>
> That's true. But the other philosophical rule is that we shouldn't
> optimize for the failure path. If someone gives us bad data they
> deserve a slow down.
> I also think leaving svc_alien_sock() is a trap for the unwary because
> it will lead to more double fget() bugs. The svc_alien_sock() function
> is weird because it returns false on success and false on failure and
> true for alien sock.
>
> >
> > Maybe instead svc_alien_sock() could return the struct socket (if
> > successful), and it could be passed to svc_addsock()???
> >
> > I would probably then change the name of svc_alien_sock()
>
> Yeah, because we don't want alien sockets, we want Earth sockets.
> Doing this is much more complicated... The name svc_get_earth_sock()
> is just a joke. Tell me what name to use if we decide to go this
> route.
>
> To be honest, I would probably still go with my v1 patch.
>
+1. I don't see a need to do this check twice. Let's optimize for the
success case and if someone sends down bogus data, then they just go
slower.
I too suggest we just go with Dan's original patch.
> regards,
> dan carpenter
>
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index e0e98b40a6e5d..affcd44f03d6b 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -689,6 +689,7 @@ static ssize_t __write_ports_names(char *buf, struct net *net)
> */
> static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred *cred)
> {
> + struct socket *so;
> char *mesg = buf;
> int fd, err;
> struct nfsd_net *nn = net_generic(net, nfsd_net_id);
> @@ -698,22 +699,30 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred
> return -EINVAL;
> trace_nfsd_ctl_ports_addfd(net, fd);
>
> - if (svc_alien_sock(net, fd)) {
> + so = svc_get_earth_sock(net, fd);
> + if (!so) {
> printk(KERN_ERR "%s: socket net is different to NFSd's one\n", __func__);
> return -EINVAL;
> }
>
> err = nfsd_create_serv(net);
> if (err != 0)
> - return err;
> + goto out_put_sock;
>
> - err = svc_addsock(nn->nfsd_serv, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
> + err = svc_addsock(nn->nfsd_serv, so, buf, SIMPLE_TRANSACTION_LIMIT, cred);
> + if (err)
> + goto out_put_net;
>
> - if (err >= 0 &&
> - !nn->nfsd_serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
> + if (!nn->nfsd_serv->sv_nrthreads && !xchg(&nn->keep_active, 1))
> svc_get(nn->nfsd_serv);
>
> nfsd_put(net);
> + return 0;
> +
> +out_put_net:
> + nfsd_put(net);
> +out_put_sock:
> + sockfd_put(so);
> return err;
> }
>
> diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
> index d16ae621782c0..2422d260591bb 100644
> --- a/include/linux/sunrpc/svcsock.h
> +++ b/include/linux/sunrpc/svcsock.h
> @@ -61,8 +61,8 @@ int svc_recv(struct svc_rqst *, long);
> void svc_send(struct svc_rqst *rqstp);
> void svc_drop(struct svc_rqst *);
> void svc_sock_update_bufs(struct svc_serv *serv);
> -bool svc_alien_sock(struct net *net, int fd);
> -int svc_addsock(struct svc_serv *serv, const int fd,
> +struct socket *svc_get_earth_sock(struct net *net, int fd);
> +int svc_addsock(struct svc_serv *serv, struct socket *so,
> char *name_return, const size_t len,
> const struct cred *cred);
> void svc_init_xprt_sock(void);
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 46845cb6465d7..78f6ae9fa42d4 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1474,21 +1474,20 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
> return svsk;
> }
>
> -bool svc_alien_sock(struct net *net, int fd)
> +struct socket *svc_get_earth_sock(struct net *net, int fd)
> {
> int err;
> struct socket *sock = sockfd_lookup(fd, &err);
> - bool ret = false;
>
> if (!sock)
> - goto out;
> - if (sock_net(sock->sk) != net)
> - ret = true;
> - sockfd_put(sock);
> -out:
> - return ret;
> + return NULL;
> + if (sock_net(sock->sk) != net) {
> + sockfd_put(sock);
> + return NULL;
> + }
> + return sock;
> }
> -EXPORT_SYMBOL_GPL(svc_alien_sock);
> +EXPORT_SYMBOL_GPL(svc_get_earth_sock);
>
> /**
> * svc_addsock - add a listener socket to an RPC service
> @@ -1502,36 +1501,27 @@ EXPORT_SYMBOL_GPL(svc_alien_sock);
> * Name is terminated with '\n'. On error, returns a negative errno
> * value.
> */
> -int svc_addsock(struct svc_serv *serv, const int fd, char *name_return,
> +int svc_addsock(struct svc_serv *serv, struct socket *so, char *name_return,
> const size_t len, const struct cred *cred)
> {
> - int err = 0;
> - struct socket *so = sockfd_lookup(fd, &err);
> struct svc_sock *svsk = NULL;
> struct sockaddr_storage addr;
> struct sockaddr *sin = (struct sockaddr *)&addr;
> int salen;
>
> - if (!so)
> - return err;
> - err = -EAFNOSUPPORT;
> if ((so->sk->sk_family != PF_INET) && (so->sk->sk_family != PF_INET6))
> - goto out;
> - err = -EPROTONOSUPPORT;
> + return -EAFNOSUPPORT;
> if (so->sk->sk_protocol != IPPROTO_TCP &&
> so->sk->sk_protocol != IPPROTO_UDP)
> - goto out;
> - err = -EISCONN;
> + return -EPROTONOSUPPORT;
> if (so->state > SS_UNCONNECTED)
> - goto out;
> - err = -ENOENT;
> + return -EISCONN;
> if (!try_module_get(THIS_MODULE))
> - goto out;
> + return -ENOENT;
> svsk = svc_setup_socket(serv, so, SVC_SOCK_DEFAULTS);
> if (IS_ERR(svsk)) {
> module_put(THIS_MODULE);
> - err = PTR_ERR(svsk);
> - goto out;
> + return PTR_ERR(svsk);
> }
> salen = kernel_getsockname(svsk->sk_sock, sin);
> if (salen >= 0)
> @@ -1539,9 +1529,6 @@ int svc_addsock(struct svc_serv *serv, const int fd, char *name_return,
> svsk->sk_xprt.xpt_cred = get_cred(cred);
> svc_add_new_perm_xprt(serv, &svsk->sk_xprt);
> return svc_one_sock_name(svsk, name_return, len);
> -out:
> - sockfd_put(so);
> - return err;
> }
> EXPORT_SYMBOL_GPL(svc_addsock);
>
>
>
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
