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Commit e77340e0 authored by Chuck Lever's avatar Chuck Lever Committed by J. Bruce Fields
Browse files

svcrdma: Improve Read chunk sanity checking 



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

- Reject RPC-over-RDMA messages that contain more than one Read chunk,
  since this implementation currently does not support more than one
  per RPC transaction.

- Ensure that segment lengths are not crazy.

- Remove the segment count check. With a 1KB inline threshold, the
  largest number of Read segments that can be conveyed is about 40
  (for a RDMA_NOMSG Call message). This is nowhere near
  RPCSVC_MAXPAGES. As far as I can tell, that was just a sanity
  check and does not enforce an implementation limit.

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent a80a3234

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

+37 −18
Original line number Original line Diff line number Diff line
@@ -117,15 +117,47 @@ static void rdma_build_arg_xdr(struct svc_rqst *rqstp, 
	rqstp->rq_arg.tail[0].iov_len = 0;

	rqstp->rq_arg.tail[0].iov_len = 0;

}

}





static __be32 *xdr_check_read_list(__be32 *p, __be32 *end)

/* This accommodates the largest possible Position-Zero

 * Read chunk or Reply chunk, in one segment.

 */

#define MAX_BYTES_SPECIAL_SEG	((u32)((RPCSVC_MAXPAGES + 2) << PAGE_SHIFT))



/* Sanity check the Read list.

 *

 * Implementation limits:

 * - This implementation supports only one Read chunk.

 *

 * Sanity checks:

 * - Read list does not overflow buffer.

 * - Segment size limited by largest NFS data payload.

 *

 * The segment count is limited to how many segments can

 * fit in the transport header without overflowing the

 * buffer. That's about 40 Read segments for a 1KB inline

 * threshold.

 *

 * Returns pointer to the following Write list.

 */

static __be32 *xdr_check_read_list(__be32 *p, const __be32 *end)

{

{

	__be32 *next;

	u32 position;

	bool first;





	first = true;

	while (*p++ != xdr_zero) {

	while (*p++ != xdr_zero) {

		next = p + rpcrdma_readchunk_maxsz - 1;

		if (first) {

		if (next > end)

			position = be32_to_cpup(p++);

			first = false;

		} else if (be32_to_cpup(p++) != position) {

			return NULL;

		}

		p++;	/* handle */

		if (be32_to_cpup(p++) > MAX_BYTES_SPECIAL_SEG)

			return NULL;

		p += 2;	/* offset */



		if (p > end)

			return NULL;

			return NULL;

		p = next;

	}

	}

	return p;

	return p;

}

}
@@ -478,16 +510,6 @@ int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt, 
	return ret;

	return ret;

}

}





static unsigned int

rdma_rcl_chunk_count(struct rpcrdma_read_chunk *ch)

{

	unsigned int count;



	for (count = 0; ch->rc_discrim != xdr_zero; ch++)

		count++;

	return count;

}



/* If there was additional inline content, append it to the end of arg.pages.

/* If there was additional inline content, append it to the end of arg.pages.

 * Tail copy has to be done after the reader function has determined how many

 * Tail copy has to be done after the reader function has determined how many

 * pages are needed for RDMA READ.

 * pages are needed for RDMA READ.
@@ -567,9 +589,6 @@ static int rdma_read_chunks(struct svcxprt_rdma *xprt, 
	if (!ch)

	if (!ch)

		return 0;

		return 0;





	if (rdma_rcl_chunk_count(ch) > RPCSVC_MAXPAGES)

		return -EINVAL;



	/* The request is completed when the RDMA_READs complete. The

	/* The request is completed when the RDMA_READs complete. The

	 * head context keeps all the pages that comprise the

	 * head context keeps all the pages that comprise the

	 * request.

	 * request.