[PATCH v2 07/19] svcrdma: Improve Reply chunk sanity checking

Chuck Lever
2017-06-16T15:21:17Z

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-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
---
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index cf8be18..b480893 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;
}

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