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

Replace the open-coded encode logic for rpcbind arguments with an
xdr_stream-based implementation, similar to what NFSv4 uses, to
better protect against buffer overflows.

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

1 files changed, 75 insertions, 1 deletions

diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
index 1fb1c070c19d..823d20dbad09 100644
--- a/net/sunrpc/rpcb_clnt.c
+++ b/net/sunrpc/rpcb_clnt.c
@@ -708,6 +708,30 @@ static int rpcb_encode_mapping(struct rpc_rqst *req, __be32 *p,
         return 0;
 }
 
+static int rpcb_enc_mapping(struct rpc_rqst *req, __be32 *p,
+                            const struct rpcbind_args *rpcb)
+{
+        struct rpc_task *task = req->rq_task;
+        struct xdr_stream xdr;
+
+        dprintk("RPC: %5u encoding PMAP_%s call (%u, %u, %d, %u)\n",
+                        task->tk_pid, task->tk_msg.rpc_proc->p_name,
+                        rpcb->r_prog, rpcb->r_vers, rpcb->r_prot, rpcb->r_port);
+
+        xdr_init_encode(&xdr, &req->rq_snd_buf, p);
+
+        p = xdr_reserve_space(&xdr, sizeof(__be32) * RPCB_mappingargs_sz);
+        if (unlikely(p == NULL))
+                return -EIO;
+
+        *p++ = htonl(rpcb->r_prog);
+        *p++ = htonl(rpcb->r_vers);
+        *p++ = htonl(rpcb->r_prot);
+        *p   = htonl(rpcb->r_port);
+
+        return 0;
+}
+
 static int rpcb_decode_getport(struct rpc_rqst *req, __be32 *p,
                                unsigned short *portp)
 {
@@ -746,6 +770,56 @@ static int rpcb_encode_getaddr(struct rpc_rqst *req, __be32 *p,
         return 0;
 }
 
+static int encode_rpcb_string(struct xdr_stream *xdr, const char *string,
+                                const u32 maxstrlen)
+{
+        u32 len;
+        __be32 *p;
+
+        if (unlikely(string == NULL))
+                return -EIO;
+        len = strlen(string);
+        if (unlikely(len > maxstrlen))
+                return -EIO;
+
+        p = xdr_reserve_space(xdr, sizeof(__be32) + len);
+        if (unlikely(p == NULL))
+                return -EIO;
+        xdr_encode_opaque(p, string, len);
+
+        return 0;
+}
+
+static int rpcb_enc_getaddr(struct rpc_rqst *req, __be32 *p,
+                            const struct rpcbind_args *rpcb)
+{
+        struct rpc_task *task = req->rq_task;
+        struct xdr_stream xdr;
+
+        dprintk("RPC: %5u encoding RPCB_%s call (%u, %u, '%s', '%s')\n",
+                        task->tk_pid, task->tk_msg.rpc_proc->p_name,
+                        rpcb->r_prog, rpcb->r_vers,
+                        rpcb->r_netid, rpcb->r_addr);
+
+        xdr_init_encode(&xdr, &req->rq_snd_buf, p);
+
+        p = xdr_reserve_space(&xdr,
+                        sizeof(__be32) * (RPCB_program_sz + RPCB_version_sz));
+        if (unlikely(p == NULL))
+                return -EIO;
+        *p++ = htonl(rpcb->r_prog);
+        *p = htonl(rpcb->r_vers);
+
+        if (encode_rpcb_string(&xdr, rpcb->r_netid, RPCBIND_MAXNETIDLEN))
+                return -EIO;
+        if (encode_rpcb_string(&xdr, rpcb->r_addr, RPCBIND_MAXUADDRLEN))
+                return -EIO;
+        if (encode_rpcb_string(&xdr, rpcb->r_owner, RPCB_MAXOWNERLEN))
+                return -EIO;
+
+        return 0;
+}
+
 static int rpcb_decode_getaddr(struct rpc_rqst *req, __be32 *p,
                                unsigned short *portp)
 {
@@ -812,7 +886,7 @@ out_err:
 #define PROC(proc, argtype, restype)                                    \
         [RPCBPROC_##proc] = {                                           \
                 .p_proc         = RPCBPROC_##proc,                      \
-                .p_encode       = (kxdrproc_t) rpcb_encode_##argtype,   \
+                .p_encode       = (kxdrproc_t) rpcb_enc_##argtype,      \
                 .p_decode       = (kxdrproc_t) rpcb_decode_##restype,   \
                 .p_arglen       = RPCB_##argtype##args_sz,              \
                 .p_replen       = RPCB_##restype##res_sz,               \