SUNRPC: Introduce new xdr_stream-based decoders to rpcb_clnt.c

Replace the open-coded decode logic for PMAP_GETPORT/RPCB_GETADDR with
an xdr_stream-based implementation, similar to what NFSv4 uses, to
protect against buffer overflows.  The new implementation also checks
that the incoming port number is reasonable.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 77 insertions, 3 deletions

diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
index fe183af5cc72..88de754e3b02 100644
--- a/net/sunrpc/rpcb_clnt.c
+++ b/net/sunrpc/rpcb_clnt.c
@@ -454,7 +454,7 @@ int rpcb_getport_sync(struct sockaddr_in *sin, u32 prog, u32 vers, int prot)
         struct rpc_message msg = {
                 .rpc_proc       = &rpcb_procedures2[RPCBPROC_GETPORT],
                 .rpc_argp       = &map,
-                .rpc_resp       = &map.r_port,
+                .rpc_resp       = &map,
         };
         struct rpc_clnt *rpcb_clnt;
         int status;
@@ -484,7 +484,7 @@ static struct rpc_task *rpcb_call_async(struct rpc_clnt *rpcb_clnt, struct rpcbi
         struct rpc_message msg = {
                 .rpc_proc = proc,
                 .rpc_argp = map,
-                .rpc_resp = &map->r_port,
+                .rpc_resp = map,
         };
         struct rpc_task_setup task_setup_data = {
                 .rpc_client = rpcb_clnt,
@@ -727,6 +727,31 @@ static int rpcb_decode_getport(struct rpc_rqst *req, __be32 *p,
         return 0;
 }
 
+static int rpcb_dec_getport(struct rpc_rqst *req, __be32 *p,
+                            struct rpcbind_args *rpcb)
+{
+        struct rpc_task *task = req->rq_task;
+        struct xdr_stream xdr;
+        unsigned long port;
+
+        xdr_init_decode(&xdr, &req->rq_rcv_buf, p);
+
+        rpcb->r_port = 0;
+
+        p = xdr_inline_decode(&xdr, sizeof(__be32));
+        if (unlikely(p == NULL))
+                return -EIO;
+
+        port = ntohl(*p);
+        dprintk("RPC: %5u PMAP_%s result: %lu\n", task->tk_pid,
+                        task->tk_msg.rpc_proc->p_name, port);
+        if (unlikely(port > USHORT_MAX))
+                return -EIO;
+
+        rpcb->r_port = port;
+        return 0;
+}
+
 static int rpcb_decode_set(struct rpc_rqst *req, __be32 *p,
                            unsigned int *boolp)
 {
@@ -871,11 +896,60 @@ out_err:
         return -EIO;
 }
 
+static int rpcb_dec_getaddr(struct rpc_rqst *req, __be32 *p,
+                            struct rpcbind_args *rpcb)
+{
+        struct sockaddr_storage address;
+        struct sockaddr *sap = (struct sockaddr *)&address;
+        struct rpc_task *task = req->rq_task;
+        struct xdr_stream xdr;
+        u32 len;
+
+        rpcb->r_port = 0;
+
+        xdr_init_decode(&xdr, &req->rq_rcv_buf, p);
+
+        p = xdr_inline_decode(&xdr, sizeof(__be32));
+        if (unlikely(p == NULL))
+                goto out_fail;
+        len = ntohl(*p);
+
+        /*
+         * If the returned universal address is a null string,
+         * the requested RPC service was not registered.
+         */
+        if (len == 0) {
+                dprintk("RPC: %5u RPCB reply: program not registered\n",
+                                task->tk_pid);
+                return 0;
+        }
+
+        if (unlikely(len > RPCBIND_MAXUADDRLEN))
+                goto out_fail;
+
+        p = xdr_inline_decode(&xdr, len);
+        if (unlikely(p == NULL))
+                goto out_fail;
+        dprintk("RPC: %5u RPCB_%s reply: %s\n", task->tk_pid,
+                        task->tk_msg.rpc_proc->p_name, (char *)p);
+
+        if (rpc_uaddr2sockaddr((char *)p, len, sap, sizeof(address)) == 0)
+                goto out_fail;
+        rpcb->r_port = rpc_get_port(sap);
+
+        return 0;
+
+out_fail:
+        dprintk("RPC: %5u malformed RPCB_%s reply\n",
+                        task->tk_pid, task->tk_msg.rpc_proc->p_name);
+        return -EIO;
+}
+
 #define PROC(proc, argtype, restype)                                    \
         [RPCBPROC_##proc] = {                                           \
                 .p_proc         = RPCBPROC_##proc,                      \
                 .p_encode       = (kxdrproc_t) rpcb_enc_##argtype,      \
-                .p_decode       = (kxdrproc_t) rpcb_decode_##restype,   \
+                .p_decode       = (kxdrproc_t) rpcb_dec_##restype,      \
                 .p_arglen       = RPCB_##argtype##args_sz,              \
                 .p_replen       = RPCB_##restype##res_sz,               \
                 .p_statidx      = RPCBPROC_##proc,                      \