SUNRPC: Use struct xdr_stream when decoding RPC Reply header

Modernize and harden the code path that parses an RPC Reply
message.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

7 files changed, 243 insertions, 201 deletions

diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h
index 96e237f8e60b..c51e1893f77e 100644
--- a/include/linux/sunrpc/auth.h
+++ b/include/linux/sunrpc/auth.h
@@ -134,11 +134,12 @@ struct rpc_credops {
         int                     (*crmarshal)(struct rpc_task *task,
                                              struct xdr_stream *xdr);
         int                     (*crrefresh)(struct rpc_task *);
-        __be32 *                (*crvalidate)(struct rpc_task *, __be32 *);
+        int                     (*crvalidate)(struct rpc_task *task,
+                                              struct xdr_stream *xdr);
         int                     (*crwrap_req)(struct rpc_task *task,
                                               struct xdr_stream *xdr);
-        int                     (*crunwrap_resp)(struct rpc_task *, kxdrdproc_t,
-                                                void *, __be32 *, void *);
+        int                     (*crunwrap_resp)(struct rpc_task *task,
+                                                 struct xdr_stream *xdr);
         int                     (*crkey_timeout)(struct rpc_cred *);
         char *                  (*crstringify_acceptor)(struct rpc_cred *);
         bool                    (*crneed_reencode)(struct rpc_task *);
@@ -168,12 +169,16 @@ struct rpc_cred *	rpcauth_lookupcred(struct rpc_auth *, int);
 void                    put_rpccred(struct rpc_cred *);
 int                     rpcauth_marshcred(struct rpc_task *task,
                                           struct xdr_stream *xdr);
-__be32 *                rpcauth_checkverf(struct rpc_task *, __be32 *);
+int                     rpcauth_checkverf(struct rpc_task *task,
+                                          struct xdr_stream *xdr);
 int                     rpcauth_wrap_req_encode(struct rpc_task *task,
                                                 struct xdr_stream *xdr);
 int                     rpcauth_wrap_req(struct rpc_task *task,
                                          struct xdr_stream *xdr);
-int                     rpcauth_unwrap_resp(struct rpc_task *task, kxdrdproc_t decode, void *rqstp, __be32 *data, void *obj);
+int                     rpcauth_unwrap_resp_decode(struct rpc_task *task,
+                                                   struct xdr_stream *xdr);
+int                     rpcauth_unwrap_resp(struct rpc_task *task,
+                                            struct xdr_stream *xdr);
 bool                    rpcauth_xmit_need_reencode(struct rpc_task *task);
 int                     rpcauth_refreshcred(struct rpc_task *);
 void                    rpcauth_invalcred(struct rpc_task *);
diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index c54041950cc0..65af6a204b75 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -89,6 +89,7 @@ xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
 
 #define rpc_auth_null   cpu_to_be32(RPC_AUTH_NULL)
 #define rpc_auth_unix   cpu_to_be32(RPC_AUTH_UNIX)
+#define rpc_auth_short  cpu_to_be32(RPC_AUTH_SHORT)
 #define rpc_auth_gss    cpu_to_be32(RPC_AUTH_GSS)
 
 #define rpc_call        cpu_to_be32(RPC_CALL)
diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index add2135d9b01..e7861026b9e5 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -17,6 +17,8 @@
 #include <linux/sunrpc/gss_api.h>
 #include <linux/spinlock.h>
 
+#include <trace/events/sunrpc.h>
+
 #define RPC_CREDCACHE_DEFAULT_HASHBITS  (4)
 struct rpc_cred_cache {
         struct hlist_head       *hashtable;
@@ -773,14 +775,6 @@ int rpcauth_marshcred(struct rpc_task *task, struct xdr_stream *xdr)
         return ops->crmarshal(task, xdr);
 }
 
-__be32 *
-rpcauth_checkverf(struct rpc_task *task, __be32 *p)
-{
-        struct rpc_cred *cred = task->tk_rqstp->rq_cred;
-
-        return cred->cr_ops->crvalidate(task, p);
-}
-
 /**
  * rpcauth_wrap_req_encode - XDR encode the RPC procedure
  * @task: controlling RPC task
@@ -814,27 +808,52 @@ int rpcauth_wrap_req(struct rpc_task *task, struct xdr_stream *xdr)
         return ops->crwrap_req(task, xdr);
 }
 
-static int
-rpcauth_unwrap_req_decode(kxdrdproc_t decode, struct rpc_rqst *rqstp,
-                          __be32 *data, void *obj)
+/**
+ * rpcauth_checkverf - Validate verifier in RPC Reply header
+ * @task: controlling RPC task
+ * @xdr: xdr_stream containing RPC Reply header
+ *
+ * On success, @xdr is updated to point past the verifier and
+ * zero is returned. Otherwise, @xdr is in an undefined state
+ * and a negative errno is returned.
+ */
+int
+rpcauth_checkverf(struct rpc_task *task, struct xdr_stream *xdr)
 {
-        struct xdr_stream xdr;
+        const struct rpc_credops *ops = task->tk_rqstp->rq_cred->cr_ops;
 
-        xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, data, rqstp);
-        return decode(rqstp, &xdr, obj);
+        return ops->crvalidate(task, xdr);
 }
 
+/**
+ * rpcauth_unwrap_resp_decode - Invoke XDR decode function
+ * @task: controlling RPC task
+ * @xdr: stream where the Reply message resides
+ *
+ * Returns zero on success; otherwise a negative errno is returned.
+ */
 int
-rpcauth_unwrap_resp(struct rpc_task *task, kxdrdproc_t decode, void *rqstp,
-                __be32 *data, void *obj)
+rpcauth_unwrap_resp_decode(struct rpc_task *task, struct xdr_stream *xdr)
 {
-        struct rpc_cred *cred = task->tk_rqstp->rq_cred;
+        kxdrdproc_t decode = task->tk_msg.rpc_proc->p_decode;
+
+        return decode(task->tk_rqstp, xdr, task->tk_msg.rpc_resp);
+}
+EXPORT_SYMBOL_GPL(rpcauth_unwrap_resp_decode);
+
+/**
+ * rpcauth_unwrap_resp - Invoke unwrap and decode function for the cred
+ * @task: controlling RPC task
+ * @xdr: stream where the Reply message resides
+ *
+ * Returns zero on success; otherwise a negative errno is returned.
+ */
+int
+rpcauth_unwrap_resp(struct rpc_task *task, struct xdr_stream *xdr)
+{
+        const struct rpc_credops *ops = task->tk_rqstp->rq_cred->cr_ops;
 
-        if (cred->cr_ops->crunwrap_resp)
-                return cred->cr_ops->crunwrap_resp(task, decode, rqstp,
-                                                   data, obj);
-        /* By default, we decode the arguments normally. */
-        return rpcauth_unwrap_req_decode(decode, rqstp, data, obj);
+        return ops->crunwrap_resp(task, xdr);
 }
 
 bool
diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index b333b1bdad45..206788e8b787 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -1671,59 +1671,62 @@ gss_refresh_null(struct rpc_task *task)
         return 0;
 }
 
-static __be32 *
-gss_validate(struct rpc_task *task, __be32 *p)
+static int
+gss_validate(struct rpc_task *task, struct xdr_stream *xdr)
 {
         struct rpc_cred *cred = task->tk_rqstp->rq_cred;
         struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
-        __be32          *seq = NULL;
+        __be32          *p, *seq = NULL;
         struct kvec     iov;
         struct xdr_buf  verf_buf;
         struct xdr_netobj mic;
-        u32             flav,len;
-        u32             maj_stat;
-        __be32          *ret = ERR_PTR(-EIO);
+        u32             len, maj_stat;
+        int             status;
 
-        dprintk("RPC: %5u %s\n", task->tk_pid, __func__);
+        p = xdr_inline_decode(xdr, 2 * sizeof(*p));
+        if (!p)
+                goto validate_failed;
+        if (*p++ != rpc_auth_gss)
+                goto validate_failed;
+        len = be32_to_cpup(p);
+        if (len > RPC_MAX_AUTH_SIZE)
+                goto validate_failed;
+        p = xdr_inline_decode(xdr, len);
+        if (!p)
+                goto validate_failed;
 
-        flav = ntohl(*p++);
-        if ((len = ntohl(*p++)) > RPC_MAX_AUTH_SIZE)
-                goto out_bad;
-        if (flav != RPC_AUTH_GSS)
-                goto out_bad;
         seq = kmalloc(4, GFP_NOFS);
         if (!seq)
-                goto out_bad;
-        *seq = htonl(task->tk_rqstp->rq_seqno);
+                goto validate_failed;
+        *seq = cpu_to_be32(task->tk_rqstp->rq_seqno);
         iov.iov_base = seq;
         iov.iov_len = 4;
         xdr_buf_from_iov(&iov, &verf_buf);
         mic.data = (u8 *)p;
         mic.len = len;
-
-        ret = ERR_PTR(-EACCES);
         maj_stat = gss_verify_mic(ctx->gc_gss_ctx, &verf_buf, &mic);
         if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                 clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
-        if (maj_stat) {
-                dprintk("RPC: %5u %s: gss_verify_mic returned error 0x%08x\n",
-                        task->tk_pid, __func__, maj_stat);
-                goto out_bad;
-        }
+        if (maj_stat)
+                goto bad_mic;
+
         /* We leave it to unwrap to calculate au_rslack. For now we just
          * calculate the length of the verifier: */
         cred->cr_auth->au_verfsize = XDR_QUADLEN(len) + 2;
+        status = 0;
+out:
         gss_put_ctx(ctx);
-        dprintk("RPC: %5u %s: gss_verify_mic succeeded.\n",
-                        task->tk_pid, __func__);
-        kfree(seq);
-        return p + XDR_QUADLEN(len);
-out_bad:
-        gss_put_ctx(ctx);
-        dprintk("RPC: %5u %s failed ret %ld.\n", task->tk_pid, __func__,
-                PTR_ERR(ret));
         kfree(seq);
-        return ret;
+        return status;
+
+validate_failed:
+        status = -EIO;
+        goto out;
+bad_mic:
+        dprintk("RPC: %5u %s: gss_verify_mic returned error 0x%08x\n",
+                task->tk_pid, __func__, maj_stat);
+        status = -EACCES;
+        goto out;
 }
 
 static int gss_wrap_req_integ(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
@@ -1921,79 +1924,98 @@ out:
         return status;
 }
 
-static inline int
+static int
+gss_unwrap_resp_auth(struct rpc_cred *cred)
+{
+        cred->cr_auth->au_rslack = cred->cr_auth->au_verfsize;
+        return 0;
+}
+
+static int
 gss_unwrap_resp_integ(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
-                struct rpc_rqst *rqstp, __be32 **p)
+                      struct rpc_rqst *rqstp, struct xdr_stream *xdr)
 {
-        struct xdr_buf  *rcv_buf = &rqstp->rq_rcv_buf;
-        struct xdr_buf integ_buf;
+        struct xdr_buf integ_buf, *rcv_buf = &rqstp->rq_rcv_buf;
+        u32 data_offset, mic_offset, integ_len, maj_stat;
         struct xdr_netobj mic;
-        u32 data_offset, mic_offset;
-        u32 integ_len;
-        u32 maj_stat;
-        int status = -EIO;
+        __be32 *p;
 
-        integ_len = ntohl(*(*p)++);
+        p = xdr_inline_decode(xdr, 2 * sizeof(*p));
+        if (unlikely(!p))
+                goto unwrap_failed;
+        integ_len = be32_to_cpup(p++);
         if (integ_len & 3)
-                return status;
-        data_offset = (u8 *)(*p) - (u8 *)rcv_buf->head[0].iov_base;
+                goto unwrap_failed;
+        data_offset = (u8 *)(p) - (u8 *)rcv_buf->head[0].iov_base;
         mic_offset = integ_len + data_offset;
         if (mic_offset > rcv_buf->len)
-                return status;
-        if (ntohl(*(*p)++) != rqstp->rq_seqno)
-                return status;
-
-        if (xdr_buf_subsegment(rcv_buf, &integ_buf, data_offset,
-                                mic_offset - data_offset))
-                return status;
+                goto unwrap_failed;
+        if (be32_to_cpup(p) != rqstp->rq_seqno)
+                goto unwrap_failed;
 
+        if (xdr_buf_subsegment(rcv_buf, &integ_buf, data_offset, integ_len))
+                goto unwrap_failed;
         if (xdr_buf_read_netobj(rcv_buf, &mic, mic_offset))
-                return status;
-
+                goto unwrap_failed;
         maj_stat = gss_verify_mic(ctx->gc_gss_ctx, &integ_buf, &mic);
         if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                 clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
         if (maj_stat != GSS_S_COMPLETE)
-                return status;
+                goto bad_mic;
+
+        cred->cr_auth->au_rslack = cred->cr_auth->au_verfsize + 2 +
+                                   1 + XDR_QUADLEN(mic.len);
         return 0;
+unwrap_failed:
+        return -EIO;
+bad_mic:
+        dprintk("RPC:       %s: gss_verify_mic returned error 0x%08x\n",
+                __func__, maj_stat);
+        return -EIO;
 }
 
-static inline int
+static int
 gss_unwrap_resp_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
-                struct rpc_rqst *rqstp, __be32 **p)
-{
-        struct xdr_buf  *rcv_buf = &rqstp->rq_rcv_buf;
-        u32 offset;
-        u32 opaque_len;
-        u32 maj_stat;
-        int status = -EIO;
-
-        opaque_len = ntohl(*(*p)++);
-        offset = (u8 *)(*p) - (u8 *)rcv_buf->head[0].iov_base;
+                     struct rpc_rqst *rqstp, struct xdr_stream *xdr)
+{
+        struct xdr_buf *rcv_buf = &rqstp->rq_rcv_buf;
+        struct kvec *head = rqstp->rq_rcv_buf.head;
+        unsigned int savedlen = rcv_buf->len;
+        u32 offset, opaque_len, maj_stat;
+        __be32 *p;
+
+        p = xdr_inline_decode(xdr, 2 * sizeof(*p));
+        if (unlikely(!p))
+                goto unwrap_failed;
+        opaque_len = be32_to_cpup(p++);
+        offset = (u8 *)(p) - (u8 *)head->iov_base;
         if (offset + opaque_len > rcv_buf->len)
-                return status;
-        /* remove padding: */
+                goto unwrap_failed;
         rcv_buf->len = offset + opaque_len;
 
         maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset, rcv_buf);
         if (maj_stat == GSS_S_CONTEXT_EXPIRED)
                 clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
         if (maj_stat != GSS_S_COMPLETE)
-                return status;
-        if (ntohl(*(*p)++) != rqstp->rq_seqno)
-                return status;
-
-        return 0;
-}
+                goto bad_unwrap;
+        /* gss_unwrap decrypted the sequence number */
+        if (be32_to_cpup(p++) != rqstp->rq_seqno)
+                goto unwrap_failed;
 
-static int
-gss_unwrap_req_decode(kxdrdproc_t decode, struct rpc_rqst *rqstp,
-                      __be32 *p, void *obj)
-{
-        struct xdr_stream xdr;
+        /* gss_unwrap redacts the opaque blob from the head iovec.
+         * rcv_buf has changed, thus the stream needs to be reset.
+         */
+        xdr_init_decode(xdr, rcv_buf, p, rqstp);
 
-        xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p, rqstp);
-        return decode(rqstp, &xdr, obj);
+        cred->cr_auth->au_rslack = cred->cr_auth->au_verfsize + 2 +
+                                   XDR_QUADLEN(savedlen - rcv_buf->len);
+        return 0;
+unwrap_failed:
+        return -EIO;
+bad_unwrap:
+        dprintk("RPC:       %s: gss_unwrap returned error 0x%08x\n",
+                __func__, maj_stat);
+        return -EIO;
 }
 
 static bool
@@ -2037,39 +2059,33 @@ out:
 }
 
 static int
-gss_unwrap_resp(struct rpc_task *task,
-                kxdrdproc_t decode, void *rqstp, __be32 *p, void *obj)
+gss_unwrap_resp(struct rpc_task *task, struct xdr_stream *xdr)
 {
-        struct rpc_cred *cred = task->tk_rqstp->rq_cred;
+        struct rpc_rqst *rqstp = task->tk_rqstp;
+        struct rpc_cred *cred = rqstp->rq_cred;
         struct gss_cred *gss_cred = container_of(cred, struct gss_cred,
                         gc_base);
         struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
-        __be32          *savedp = p;
-        struct kvec     *head = ((struct rpc_rqst *)rqstp)->rq_rcv_buf.head;
-        int             savedlen = head->iov_len;
-        int             status = -EIO;
+        int status = -EIO;
 
         if (ctx->gc_proc != RPC_GSS_PROC_DATA)
                 goto out_decode;
         switch (gss_cred->gc_service) {
         case RPC_GSS_SVC_NONE:
+                status = gss_unwrap_resp_auth(cred);
                 break;
         case RPC_GSS_SVC_INTEGRITY:
-                status = gss_unwrap_resp_integ(cred, ctx, rqstp, &p);
-                if (status)
-                        goto out;
+                status = gss_unwrap_resp_integ(cred, ctx, rqstp, xdr);
                 break;
         case RPC_GSS_SVC_PRIVACY:
-                status = gss_unwrap_resp_priv(cred, ctx, rqstp, &p);
-                if (status)
-                        goto out;
+                status = gss_unwrap_resp_priv(cred, ctx, rqstp, xdr);
                 break;
         }
-        /* take into account extra slack for integrity and privacy cases: */
-        cred->cr_auth->au_rslack = cred->cr_auth->au_verfsize + (p - savedp)
-                                                + (savedlen - head->iov_len);
+        if (status)
+                goto out;
+
 out_decode:
-        status = gss_unwrap_req_decode(decode, rqstp, p, obj);
+        status = rpcauth_unwrap_resp_decode(task, xdr);
 out:
         gss_put_ctx(ctx);
         dprintk("RPC: %5u %s returning %d\n",
diff --git a/net/sunrpc/auth_null.c b/net/sunrpc/auth_null.c
index 797f8472c21b..bf96975ffc4b 100644
--- a/net/sunrpc/auth_null.c
+++ b/net/sunrpc/auth_null.c
@@ -86,25 +86,19 @@ nul_refresh(struct rpc_task *task)
         return 0;
 }
 
-static __be32 *
-nul_validate(struct rpc_task *task, __be32 *p)
+static int
+nul_validate(struct rpc_task *task, struct xdr_stream *xdr)
 {
-        rpc_authflavor_t        flavor;
-        u32                     size;
-
-        flavor = ntohl(*p++);
-        if (flavor != RPC_AUTH_NULL) {
-                printk("RPC: bad verf flavor: %u\n", flavor);
-                return ERR_PTR(-EIO);
-        }
-
-        size = ntohl(*p++);
-        if (size != 0) {
-                printk("RPC: bad verf size: %u\n", size);
-                return ERR_PTR(-EIO);
-        }
-
-        return p;
+        __be32 *p;
+
+        p = xdr_inline_decode(xdr, 2 * sizeof(*p));
+        if (!p)
+                return -EIO;
+        if (*p++ != rpc_auth_null)
+                return -EIO;
+        if (*p != xdr_zero)
+                return -EIO;
+        return 0;
 }
 
 const struct rpc_authops authnull_ops = {
@@ -134,6 +128,7 @@ const struct rpc_credops null_credops = {
         .crwrap_req     = rpcauth_wrap_req_encode,
         .crrefresh      = nul_refresh,
         .crvalidate     = nul_validate,
+        .crunwrap_resp  = rpcauth_unwrap_resp_decode,
 };
 
 static
diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c
index 1d5b7ed9c6f7..5ea84a96f96e 100644
--- a/net/sunrpc/auth_unix.c
+++ b/net/sunrpc/auth_unix.c
@@ -160,29 +160,32 @@ unx_refresh(struct rpc_task *task)
         return 0;
 }
 
-static __be32 *
-unx_validate(struct rpc_task *task, __be32 *p)
+static int
+unx_validate(struct rpc_task *task, struct xdr_stream *xdr)
 {
-        rpc_authflavor_t        flavor;
-        u32                     size;
-
-        flavor = ntohl(*p++);
-        if (flavor != RPC_AUTH_NULL &&
-            flavor != RPC_AUTH_UNIX &&
-            flavor != RPC_AUTH_SHORT) {
-                printk("RPC: bad verf flavor: %u\n", flavor);
-                return ERR_PTR(-EIO);
-        }
+        __be32 *p;
+        u32 size;
 
-        size = ntohl(*p++);
-        if (size > RPC_MAX_AUTH_SIZE) {
-                printk("RPC: giant verf size: %u\n", size);
-                return ERR_PTR(-EIO);
+        p = xdr_inline_decode(xdr, 2 * sizeof(*p));
+        if (!p)
+                return -EIO;
+        switch (*p++) {
+        case rpc_auth_null:
+        case rpc_auth_unix:
+        case rpc_auth_short:
+                break;
+        default:
+                return -EIO;
         }
-        task->tk_rqstp->rq_cred->cr_auth->au_rslack = (size >> 2) + 2;
-        p += (size >> 2);
+        size = be32_to_cpup(p);
+        if (size > RPC_MAX_AUTH_SIZE)
+                return -EIO;
+        p = xdr_inline_decode(xdr, size);
+        if (!p)
+                return -EIO;
 
-        return p;
+        task->tk_rqstp->rq_cred->cr_auth->au_rslack = (size >> 2) + 2;
+        return 0;
 }
 
 int __init rpc_init_authunix(void)
@@ -223,4 +226,5 @@ const struct rpc_credops unix_credops = {
         .crwrap_req     = rpcauth_wrap_req_encode,
         .crrefresh      = unx_refresh,
         .crvalidate     = unx_validate,
+        .crunwrap_resp  = rpcauth_unwrap_resp_decode,
 };
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index e9735089bd66..803e93105af1 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -79,7 +79,8 @@ static void	call_connect_status(struct rpc_task *task);
 
 static int      rpc_encode_header(struct rpc_task *task,
                                   struct xdr_stream *xdr);
-static __be32   *rpc_decode_header(struct rpc_task *task);
+static int      rpc_decode_header(struct rpc_task *task,
+                                  struct xdr_stream *xdr);
 static int      rpc_ping(struct rpc_clnt *clnt);
 
 static void rpc_register_client(struct rpc_clnt *clnt)
@@ -2251,12 +2252,11 @@ call_decode(struct rpc_task *task)
 {
         struct rpc_clnt *clnt = task->tk_client;
         struct rpc_rqst *req = task->tk_rqstp;
-        kxdrdproc_t     decode = task->tk_msg.rpc_proc->p_decode;
-        __be32          *p;
+        struct xdr_stream xdr;
 
         dprint_status(task);
 
-        if (!decode) {
+        if (!task->tk_msg.rpc_proc->p_decode) {
                 task->tk_action = rpc_exit_task;
                 return;
         }
@@ -2292,29 +2292,27 @@ call_decode(struct rpc_task *task)
                 goto out_retry;
         }
 
-        p = rpc_decode_header(task);
-        if (IS_ERR(p)) {
-                if (p == ERR_PTR(-EAGAIN))
-                        goto out_retry;
+        xdr_init_decode(&xdr, &req->rq_rcv_buf,
+                        req->rq_rcv_buf.head[0].iov_base, req);
+        switch (rpc_decode_header(task, &xdr)) {
+        case 0:
+                task->tk_action = rpc_exit_task;
+                task->tk_status = rpcauth_unwrap_resp(task, &xdr);
+                dprintk("RPC: %5u %s result %d\n",
+                        task->tk_pid, __func__, task->tk_status);
                 return;
-        }
-        task->tk_action = rpc_exit_task;
-
-        task->tk_status = rpcauth_unwrap_resp(task, decode, req, p,
-                                              task->tk_msg.rpc_resp);
-
-        dprintk("RPC: %5u call_decode result %d\n", task->tk_pid,
-                        task->tk_status);
-        return;
+        case -EAGAIN:
 out_retry:
-        task->tk_status = 0;
-        /* Note: rpc_decode_header() may have freed the RPC slot */
-        if (task->tk_rqstp == req) {
-                xdr_free_bvec(&req->rq_rcv_buf);
-                req->rq_reply_bytes_recvd = req->rq_rcv_buf.len = 0;
-                if (task->tk_client->cl_discrtry)
-                        xprt_conditional_disconnect(req->rq_xprt,
-                                        req->rq_connect_cookie);
+                task->tk_status = 0;
+                /* Note: rpc_decode_header() may have freed the RPC slot */
+                if (task->tk_rqstp == req) {
+                        xdr_free_bvec(&req->rq_rcv_buf);
+                        req->rq_reply_bytes_recvd = 0;
+                        req->rq_rcv_buf.len = 0;
+                        if (task->tk_client->cl_discrtry)
+                                xprt_conditional_disconnect(req->rq_xprt,
+                                                            req->rq_connect_cookie);
+                }
         }
 }
 
@@ -2347,14 +2345,12 @@ out_fail:
         return error;
 }
 
-static noinline __be32 *
-rpc_decode_header(struct rpc_task *task)
+static noinline int
+rpc_decode_header(struct rpc_task *task, struct xdr_stream *xdr)
 {
         struct rpc_clnt *clnt = task->tk_client;
-        struct kvec *iov = &task->tk_rqstp->rq_rcv_buf.head[0];
-        int len = task->tk_rqstp->rq_rcv_buf.len >> 2;
-        __be32  *p = iov->iov_base;
         int error = -EACCES;
+        __be32 *p;
 
         /* RFC-1014 says that the representation of XDR data must be a
          * multiple of four bytes
@@ -2363,25 +2359,26 @@ rpc_decode_header(struct rpc_task *task)
          */
         if (task->tk_rqstp->rq_rcv_buf.len & 3)
                 goto out_badlen;
-        if ((len -= 3) < 0)
-                goto out_unparsable;
 
+        p = xdr_inline_decode(xdr, 3 * sizeof(*p));
+        if (!p)
+                goto out_unparsable;
         p++;    /* skip XID */
         if (*p++ != rpc_reply)
                 goto out_unparsable;
         if (*p++ != rpc_msg_accepted)
                 goto out_msg_denied;
 
-        p = rpcauth_checkverf(task, p);
-        if (IS_ERR(p))
+        error = rpcauth_checkverf(task, xdr);
+        if (error)
                 goto out_verifier;
 
-        len = p - (__be32 *)iov->iov_base - 1;
-        if (len < 0)
+        p = xdr_inline_decode(xdr, sizeof(*p));
+        if (!p)
                 goto out_unparsable;
-        switch (*p++) {
+        switch (*p) {
         case rpc_success:
-                return p;
+                return 0;
         case rpc_prog_unavail:
                 trace_rpc__prog_unavail(task);
                 error = -EPFNOSUPPORT;
@@ -2406,11 +2403,11 @@ out_garbage:
         if (task->tk_garb_retry) {
                 task->tk_garb_retry--;
                 task->tk_action = call_encode;
-                return ERR_PTR(-EAGAIN);
+                return -EAGAIN;
         }
 out_err:
         rpc_exit(task, error);
-        return ERR_PTR(error);
+        return error;
 
 out_badlen:
         trace_rpc__unparsable(task);
@@ -2424,10 +2421,12 @@ out_unparsable:
 
 out_verifier:
         trace_rpc_bad_verifier(task);
-        error = PTR_ERR(p);
         goto out_garbage;
 
 out_msg_denied:
+        p = xdr_inline_decode(xdr, sizeof(*p));
+        if (!p)
+                goto out_unparsable;
         switch (*p++) {
         case rpc_auth_error:
                 break;
@@ -2441,6 +2440,9 @@ out_msg_denied:
                 goto out_err;
         }
 
+        p = xdr_inline_decode(xdr, sizeof(*p));
+        if (!p)
+                goto out_unparsable;
         switch (*p++) {
         case rpc_autherr_rejectedcred:
         case rpc_autherr_rejectedverf:
@@ -2454,7 +2456,7 @@ out_msg_denied:
                 /* Ensure we obtain a new XID! */
                 xprt_release(task);
                 task->tk_action = call_reserve;
-                return ERR_PTR(-EAGAIN);
+                return -EAGAIN;
         case rpc_autherr_badcred:
         case rpc_autherr_badverf:
                 /* possibly garbled cred/verf? */
@@ -2463,7 +2465,7 @@ out_msg_denied:
                 task->tk_garb_retry--;
                 trace_rpc__bad_creds(task);
                 task->tk_action = call_encode;
-                return ERR_PTR(-EAGAIN);
+                return -EAGAIN;
         case rpc_autherr_tooweak:
                 trace_rpc__auth_tooweak(task);
                 pr_warn("RPC: server %s requires stronger authentication.\n",