nfsd: fix double fget() bug in __write_ports_addfd()

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 instead do
the checking inside the svc_addsock() function.

Fixes: 3064639423c4 ("nfsd: check passed socket's net matches NFSd superblock's one")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: NeilBrown <neilb@suse.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index c159817..b4fd7a7 100644 (file)
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -690,16 +690,11 @@ static ssize_t __write_ports_addfd(char *buf, struct net *net, const struct cred
        if (err != 0 || fd < 0)
                return -EINVAL;
 
-       if (svc_alien_sock(net, fd)) {
-               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;
 
-       err = svc_addsock(nn->nfsd_serv, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
+       err = svc_addsock(nn->nfsd_serv, net, fd, buf, SIMPLE_TRANSACTION_LIMIT, cred);
 
        if (err >= 0 &&
            !nn->nfsd_serv->sv_nrthreads && !xchg(&nn->keep_active, 1))

diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index d16ae62..a711604 100644 (file)
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -61,10 +61,9 @@ 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,
-                                       char *name_return, const size_t len,
-                                       const struct cred *cred);
+int            svc_addsock(struct svc_serv *serv, struct net *net,
+                           const int fd, char *name_return, const size_t len,
+                           const struct cred *cred);
 void           svc_init_xprt_sock(void);
 void           svc_cleanup_xprt_sock(void);
 struct svc_xprt *svc_sock_create(struct svc_serv *serv, int prot);

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 63fe7a3..f77cebe 100644 (file)
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1480,25 +1480,10 @@ static struct svc_sock *svc_setup_socket(struct svc_serv *serv,
        return svsk;
 }
 
-bool svc_alien_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;
-}
-EXPORT_SYMBOL_GPL(svc_alien_sock);
-
 /**
  * svc_addsock - add a listener socket to an RPC service
  * @serv: pointer to RPC service to which to add a new listener
+ * @net: caller's network namespace
  * @fd: file descriptor of the new listener
  * @name_return: pointer to buffer to fill in with name of listener
  * @len: size of the buffer
@@ -1508,8 +1493,8 @@ 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,
-               const size_t len, const struct cred *cred)
+int svc_addsock(struct svc_serv *serv, struct net *net, const int fd,
+               char *name_return, const size_t len, const struct cred *cred)
 {
        int err = 0;
        struct socket *so = sockfd_lookup(fd, &err);
@@ -1520,6 +1505,9 @@ int svc_addsock(struct svc_serv *serv, const int fd, char *name_return,
 
        if (!so)
                return err;
+       err = -EINVAL;
+       if (sock_net(so->sk) != net)
+               goto out;
        err = -EAFNOSUPPORT;
        if ((so->sk->sk_family != PF_INET) && (so->sk->sk_family != PF_INET6))
                goto out;