From: Chuck Lever <chuck.lever@oracle.com>
Date: Fri, 23 Jun 2017 17:18:00 -0400
Subject: svcrdma: Improve Reply chunk sanity checking
Patch-mainline: v4.13-rc1
Git-commit: ca5c76aba7502d52a6019358ec04bd4d734037d7
References: bsc#1103992 FATE#326009

Identify malformed transport headers and unsupported chunk
combinations as early as possible.

- Ensure that segment lengths are not crazy.

- Ensure that the Reply chunk's segment count is not crazy.

With a 1KB inline threshold, the largest number of Write segments
that can be conveyed is about 60 (for a RDMA_NOMSG Reply message).

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c |   17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -217,15 +217,20 @@ static __be32 *xdr_check_write_list(__be
 	return p;
 }
 
-static __be32 *xdr_check_reply_chunk(__be32 *p, __be32 *end)
+/* Sanity check the Reply chunk.
+ *
+ * Sanity checks:
+ * - Reply chunk does not overflow buffer.
+ * - Segment size limited by largest NFS data payload.
+ *
+ * Returns pointer to the following RPC header.
+ */
+static __be32 *xdr_check_reply_chunk(__be32 *p, const __be32 *end)
 {
-	__be32 *next;
-
 	if (*p++ != xdr_zero) {
-		next = p + 1 + be32_to_cpup(p) * rpcrdma_segment_maxsz;
-		if (next > end)
+		p = xdr_check_write_chunk(p, end, MAX_BYTES_SPECIAL_SEG);
+		if (!p)
 			return NULL;
-		p = next;
 	}
 	return p;
 }