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xprtrdma: Harden chunk list encoding against send buffer overflow
authorChuck Lever <chuck.lever@oracle.com>
Thu, 10 Aug 2017 16:47:36 +0000 (12:47 -0400)
committerAnna Schumaker <Anna.Schumaker@Netapp.com>
Fri, 11 Aug 2017 17:20:08 +0000 (13:20 -0400)
While marshaling chunk lists which are variable-length XDR objects,
check for XDR buffer overflow at every step. Measurements show no
significant changes in CPU utilization.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
net/sunrpc/xprtrdma/rpc_rdma.c

index ffa99f0..f27dbfd 100644 (file)
@@ -273,15 +273,70 @@ out_overflow:
        return -EIO;
 }
 
-static inline __be32 *
+static inline int
+encode_item_present(struct xdr_stream *xdr)
+{
+       __be32 *p;
+
+       p = xdr_reserve_space(xdr, sizeof(*p));
+       if (unlikely(!p))
+               return -EMSGSIZE;
+
+       *p = xdr_one;
+       return 0;
+}
+
+static inline int
+encode_item_not_present(struct xdr_stream *xdr)
+{
+       __be32 *p;
+
+       p = xdr_reserve_space(xdr, sizeof(*p));
+       if (unlikely(!p))
+               return -EMSGSIZE;
+
+       *p = xdr_zero;
+       return 0;
+}
+
+static void
 xdr_encode_rdma_segment(__be32 *iptr, struct rpcrdma_mw *mw)
 {
        *iptr++ = cpu_to_be32(mw->mw_handle);
        *iptr++ = cpu_to_be32(mw->mw_length);
-       return xdr_encode_hyper(iptr, mw->mw_offset);
+       xdr_encode_hyper(iptr, mw->mw_offset);
+}
+
+static int
+encode_rdma_segment(struct xdr_stream *xdr, struct rpcrdma_mw *mw)
+{
+       __be32 *p;
+
+       p = xdr_reserve_space(xdr, 4 * sizeof(*p));
+       if (unlikely(!p))
+               return -EMSGSIZE;
+
+       xdr_encode_rdma_segment(p, mw);
+       return 0;
+}
+
+static int
+encode_read_segment(struct xdr_stream *xdr, struct rpcrdma_mw *mw,
+                   u32 position)
+{
+       __be32 *p;
+
+       p = xdr_reserve_space(xdr, 6 * sizeof(*p));
+       if (unlikely(!p))
+               return -EMSGSIZE;
+
+       *p++ = xdr_one;                 /* Item present */
+       *p++ = cpu_to_be32(position);
+       xdr_encode_rdma_segment(p, mw);
+       return 0;
 }
 
-/* XDR-encode the Read list. Supports encoding a list of read
+/* Register and XDR encode the Read list. Supports encoding a list of read
  * segments that belong to a single read chunk.
  *
  * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
@@ -290,24 +345,21 @@ xdr_encode_rdma_segment(__be32 *iptr, struct rpcrdma_mw *mw)
  *   N elements, position P (same P for all chunks of same arg!):
  *    1 - PHLOO - 1 - PHLOO - ... - 1 - PHLOO - 0
  *
- * Returns a pointer to the XDR word in the RDMA header following
- * the end of the Read list, or an error pointer.
+ * Returns zero on success, or a negative errno if a failure occurred.
+ * @xdr is advanced to the next position in the stream.
+ *
+ * Only a single @pos value is currently supported.
  */
-static __be32 *
-rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt,
-                        struct rpcrdma_req *req, struct rpc_rqst *rqst,
-                        __be32 *iptr, enum rpcrdma_chunktype rtype)
+static noinline int
+rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
+                        struct rpc_rqst *rqst, enum rpcrdma_chunktype rtype)
 {
+       struct xdr_stream *xdr = &req->rl_stream;
        struct rpcrdma_mr_seg *seg;
        struct rpcrdma_mw *mw;
        unsigned int pos;
        int n, nsegs;
 
-       if (rtype == rpcrdma_noch) {
-               *iptr++ = xdr_zero;     /* item not present */
-               return iptr;
-       }
-
        pos = rqst->rq_snd_buf.head[0].iov_len;
        if (rtype == rpcrdma_areadch)
                pos = 0;
@@ -315,22 +367,17 @@ rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt,
        nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_snd_buf, pos,
                                     rtype, seg);
        if (nsegs < 0)
-               return ERR_PTR(nsegs);
+               return nsegs;
 
        do {
                n = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
                                                 false, &mw);
                if (n < 0)
-                       return ERR_PTR(n);
+                       return n;
                rpcrdma_push_mw(mw, &req->rl_registered);
 
-               *iptr++ = xdr_one;      /* item present */
-
-               /* All read segments in this chunk
-                * have the same "position".
-                */
-               *iptr++ = cpu_to_be32(pos);
-               iptr = xdr_encode_rdma_segment(iptr, mw);
+               if (encode_read_segment(xdr, mw, pos) < 0)
+                       return -EMSGSIZE;
 
                dprintk("RPC: %5u %s: pos %u %u@0x%016llx:0x%08x (%s)\n",
                        rqst->rq_task->tk_pid, __func__, pos,
@@ -342,13 +389,12 @@ rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt,
                nsegs -= n;
        } while (nsegs);
 
-       /* Finish Read list */
-       *iptr++ = xdr_zero;     /* Next item not present */
-       return iptr;
+       return 0;
 }
 
-/* XDR-encode the Write list. Supports encoding a list containing
- * one array of plain segments that belong to a single write chunk.
+/* Register and XDR encode the Write list. Supports encoding a list
+ * containing one array of plain segments that belong to a single
+ * write chunk.
  *
  * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
  *
@@ -356,43 +402,45 @@ rpcrdma_encode_read_list(struct rpcrdma_xprt *r_xprt,
  *   N elements:
  *    1 - N - HLOO - HLOO - ... - HLOO - 0
  *
- * Returns a pointer to the XDR word in the RDMA header following
- * the end of the Write list, or an error pointer.
+ * Returns zero on success, or a negative errno if a failure occurred.
+ * @xdr is advanced to the next position in the stream.
+ *
+ * Only a single Write chunk is currently supported.
  */
-static __be32 *
+static noinline int
 rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
-                         struct rpc_rqst *rqst, __be32 *iptr,
-                         enum rpcrdma_chunktype wtype)
+                         struct rpc_rqst *rqst, enum rpcrdma_chunktype wtype)
 {
+       struct xdr_stream *xdr = &req->rl_stream;
        struct rpcrdma_mr_seg *seg;
        struct rpcrdma_mw *mw;
        int n, nsegs, nchunks;
        __be32 *segcount;
 
-       if (wtype != rpcrdma_writech) {
-               *iptr++ = xdr_zero;     /* no Write list present */
-               return iptr;
-       }
-
        seg = req->rl_segments;
        nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_rcv_buf,
                                     rqst->rq_rcv_buf.head[0].iov_len,
                                     wtype, seg);
        if (nsegs < 0)
-               return ERR_PTR(nsegs);
+               return nsegs;
 
-       *iptr++ = xdr_one;      /* Write list present */
-       segcount = iptr++;      /* save location of segment count */
+       if (encode_item_present(xdr) < 0)
+               return -EMSGSIZE;
+       segcount = xdr_reserve_space(xdr, sizeof(*segcount));
+       if (unlikely(!segcount))
+               return -EMSGSIZE;
+       /* Actual value encoded below */
 
        nchunks = 0;
        do {
                n = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
                                                 true, &mw);
                if (n < 0)
-                       return ERR_PTR(n);
+                       return n;
                rpcrdma_push_mw(mw, &req->rl_registered);
 
-               iptr = xdr_encode_rdma_segment(iptr, mw);
+               if (encode_rdma_segment(xdr, mw) < 0)
+                       return -EMSGSIZE;
 
                dprintk("RPC: %5u %s: %u@0x016%llx:0x%08x (%s)\n",
                        rqst->rq_task->tk_pid, __func__,
@@ -409,13 +457,11 @@ rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
        /* Update count of segments in this Write chunk */
        *segcount = cpu_to_be32(nchunks);
 
-       /* Finish Write list */
-       *iptr++ = xdr_zero;     /* Next item not present */
-       return iptr;
+       return 0;
 }
 
-/* XDR-encode the Reply chunk. Supports encoding an array of plain
- * segments that belong to a single write (reply) chunk.
+/* Register and XDR encode the Reply chunk. Supports encoding an array
+ * of plain segments that belong to a single write (reply) chunk.
  *
  * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
  *
@@ -423,41 +469,41 @@ rpcrdma_encode_write_list(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
  *   N elements:
  *    1 - N - HLOO - HLOO - ... - HLOO
  *
- * Returns a pointer to the XDR word in the RDMA header following
- * the end of the Reply chunk, or an error pointer.
+ * Returns zero on success, or a negative errno if a failure occurred.
+ * @xdr is advanced to the next position in the stream.
  */
-static __be32 *
-rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt,
-                          struct rpcrdma_req *req, struct rpc_rqst *rqst,
-                          __be32 *iptr, enum rpcrdma_chunktype wtype)
+static noinline int
+rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
+                          struct rpc_rqst *rqst, enum rpcrdma_chunktype wtype)
 {
+       struct xdr_stream *xdr = &req->rl_stream;
        struct rpcrdma_mr_seg *seg;
        struct rpcrdma_mw *mw;
        int n, nsegs, nchunks;
        __be32 *segcount;
 
-       if (wtype != rpcrdma_replych) {
-               *iptr++ = xdr_zero;     /* no Reply chunk present */
-               return iptr;
-       }
-
        seg = req->rl_segments;
        nsegs = rpcrdma_convert_iovs(r_xprt, &rqst->rq_rcv_buf, 0, wtype, seg);
        if (nsegs < 0)
-               return ERR_PTR(nsegs);
+               return nsegs;
 
-       *iptr++ = xdr_one;      /* Reply chunk present */
-       segcount = iptr++;      /* save location of segment count */
+       if (encode_item_present(xdr) < 0)
+               return -EMSGSIZE;
+       segcount = xdr_reserve_space(xdr, sizeof(*segcount));
+       if (unlikely(!segcount))
+               return -EMSGSIZE;
+       /* Actual value encoded below */
 
        nchunks = 0;
        do {
                n = r_xprt->rx_ia.ri_ops->ro_map(r_xprt, seg, nsegs,
                                                 true, &mw);
                if (n < 0)
-                       return ERR_PTR(n);
+                       return n;
                rpcrdma_push_mw(mw, &req->rl_registered);
 
-               iptr = xdr_encode_rdma_segment(iptr, mw);
+               if (encode_rdma_segment(xdr, mw) < 0)
+                       return -EMSGSIZE;
 
                dprintk("RPC: %5u %s: %u@0x%016llx:0x%08x (%s)\n",
                        rqst->rq_task->tk_pid, __func__,
@@ -474,7 +520,7 @@ rpcrdma_encode_reply_chunk(struct rpcrdma_xprt *r_xprt,
        /* Update count of segments in the Reply chunk */
        *segcount = cpu_to_be32(nchunks);
 
-       return iptr;
+       return 0;
 }
 
 /* Prepare the RPC-over-RDMA header SGE.
@@ -676,24 +722,21 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
        struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
        struct xdr_stream *xdr = &req->rl_stream;
        enum rpcrdma_chunktype rtype, wtype;
-       struct rpcrdma_msg *headerp;
        bool ddp_allowed;
-       ssize_t hdrlen;
-       __be32 *iptr;
        __be32 *p;
+       int ret;
 
 #if defined(CONFIG_SUNRPC_BACKCHANNEL)
        if (test_bit(RPC_BC_PA_IN_USE, &rqst->rq_bc_pa_state))
                return rpcrdma_bc_marshal_reply(rqst);
 #endif
 
-       headerp = rdmab_to_msg(req->rl_rdmabuf);
        rpcrdma_set_xdrlen(&req->rl_hdrbuf, 0);
        xdr_init_encode(xdr, &req->rl_hdrbuf,
                        req->rl_rdmabuf->rg_base);
 
        /* Fixed header fields */
-       iptr = ERR_PTR(-EMSGSIZE);
+       ret = -EMSGSIZE;
        p = xdr_reserve_space(xdr, 4 * sizeof(*p));
        if (!p)
                goto out_err;
@@ -775,37 +818,50 @@ rpcrdma_marshal_req(struct rpcrdma_xprt *r_xprt, struct rpc_rqst *rqst)
         * send a Call message with a Position Zero Read chunk and a
         * regular Read chunk at the same time.
         */
-       iptr = headerp->rm_body.rm_chunks;
-       iptr = rpcrdma_encode_read_list(r_xprt, req, rqst, iptr, rtype);
-       if (IS_ERR(iptr))
+       if (rtype != rpcrdma_noch) {
+               ret = rpcrdma_encode_read_list(r_xprt, req, rqst, rtype);
+               if (ret)
+                       goto out_err;
+       }
+       ret = encode_item_not_present(xdr);
+       if (ret)
                goto out_err;
-       iptr = rpcrdma_encode_write_list(r_xprt, req, rqst, iptr, wtype);
-       if (IS_ERR(iptr))
+
+       if (wtype == rpcrdma_writech) {
+               ret = rpcrdma_encode_write_list(r_xprt, req, rqst, wtype);
+               if (ret)
+                       goto out_err;
+       }
+       ret = encode_item_not_present(xdr);
+       if (ret)
                goto out_err;
-       iptr = rpcrdma_encode_reply_chunk(r_xprt, req, rqst, iptr, wtype);
-       if (IS_ERR(iptr))
+
+       if (wtype != rpcrdma_replych)
+               ret = encode_item_not_present(xdr);
+       else
+               ret = rpcrdma_encode_reply_chunk(r_xprt, req, rqst, wtype);
+       if (ret)
                goto out_err;
-       hdrlen = (unsigned char *)iptr - (unsigned char *)headerp;
 
-       dprintk("RPC: %5u %s: %s/%s: hdrlen %zd\n",
+       dprintk("RPC: %5u %s: %s/%s: hdrlen %u rpclen\n",
                rqst->rq_task->tk_pid, __func__,
                transfertypes[rtype], transfertypes[wtype],
-               hdrlen);
+               xdr_stream_pos(xdr));
 
-       if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req, hdrlen,
+       if (!rpcrdma_prepare_send_sges(&r_xprt->rx_ia, req,
+                                      xdr_stream_pos(xdr),
                                       &rqst->rq_snd_buf, rtype)) {
-               iptr = ERR_PTR(-EIO);
+               ret = -EIO;
                goto out_err;
        }
        return 0;
 
 out_err:
-       if (PTR_ERR(iptr) != -ENOBUFS) {
-               pr_err("rpcrdma: rpcrdma_marshal_req failed, status %ld\n",
-                      PTR_ERR(iptr));
+       if (ret != -ENOBUFS) {
+               pr_err("rpcrdma: header marshaling failed (%d)\n", ret);
                r_xprt->rx_stats.failed_marshal_count++;
        }
-       return PTR_ERR(iptr);
+       return ret;
 }
 
 /**