svcrdma: Improve Reply chunk sanity checking

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>

1 files changed, 11 insertions, 6 deletions

diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index cf8be18f297a..b48089314f85 100644
--- 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(__be32 *p, const __be32 *end)
         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;
 }