[PATCH 1/6] svcrdma: validate Read chunk positions before reconstruction

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

The RPC/RDMA Read chunk position field is supplied by the remote
client and stored verbatim in the parsed chunk list.
xdr_count_read_segments() checks only 4-byte alignment; it never
compares the position against the received inline body length.

In the single-chunk path, svc_rdma_read_complete_one() splits the
head and tail kvecs at ch_position.  A position past the inline
body underflows the tail length, exposing adjacent slab memory to
the upper XDR decoder.

In the multi-chunk path, svc_rdma_read_multiple_chunks() computes
gap lengths between chunks as unsigned subtractions from
ch_position.  Overlapping Read chunks cause these subtractions to
underflow.  A final position past the inline body likewise
underflows the trailing gap length.  svc_rdma_copy_inline_range()
then copies past the receive buffer into request pages that are
returned to the client through the Reply channel.

Bound inline-range copies in svc_rdma_copy_inline_range() against
the decoded inline RPC body saved in rc_saved_arg.  Reject a
single Read chunk positioned beyond that body, and reject
multi-chunk lists where accumulated read bytes exceed the next
chunk's position.  Apply the same position and overlap checks in
the call-chunk interleaving path.

Fixes: d96962e6d0e2 ("svcrdma: Use the new parsed chunk list when pulling Read chunks")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/svc_rdma_rw.c | 38 ++++++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 8 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index c535e6de9654..eb4bc56ed387 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -1065,7 +1065,7 @@ static int svc_rdma_build_read_chunk(struct svc_rqst *rqstp,
  * svc_rdma_copy_inline_range - Copy part of the inline content into pages
  * @rqstp: RPC transaction context
  * @head: context for ongoing I/O
- * @offset: offset into the Receive buffer of region to copy
+ * @offset: offset into the inline content of region to copy
  * @remaining: length of region to copy
  *
  * Take a page at a time from rqstp->rq_pages and copy the inline
@@ -1082,9 +1082,13 @@ static int svc_rdma_copy_inline_range(struct svc_rqst *rqstp,
 				      unsigned int offset,
 				      unsigned int remaining)
 {
-	unsigned char *dst, *src = head->rc_recv_buf;
+	unsigned char *dst, *src = head->rc_saved_arg.head[0].iov_base;
+	unsigned int inline_len = head->rc_saved_arg.head[0].iov_len;
 	unsigned int page_no, numpages;
 
+	if (offset > inline_len || remaining > inline_len - offset)
+		return -EINVAL;
+
 	numpages = PAGE_ALIGN(head->rc_pageoff + remaining) >> PAGE_SHIFT;
 	for (page_no = 0; page_no < numpages; page_no++) {
 		unsigned int page_len;
@@ -1135,9 +1139,10 @@ svc_rdma_read_multiple_chunks(struct svc_rqst *rqstp,
 {
 	const struct svc_rdma_pcl *pcl = &head->rc_read_pcl;
 	struct svc_rdma_chunk *chunk, *next;
-	unsigned int start, length;
+	unsigned int inline_len, start, length;
 	int ret;
 
+	inline_len = head->rc_saved_arg.head[0].iov_len;
 	start = 0;
 	chunk = pcl_first_chunk(pcl);
 	length = chunk->ch_position;
@@ -1155,6 +1160,8 @@ svc_rdma_read_multiple_chunks(struct svc_rqst *rqstp,
 			break;
 
 		start += length;
+		if (head->rc_readbytes > next->ch_position)
+			return -EINVAL;
 		length = next->ch_position - head->rc_readbytes;
 		ret = svc_rdma_copy_inline_range(rqstp, head, start, length);
 		if (ret < 0)
@@ -1162,7 +1169,9 @@ svc_rdma_read_multiple_chunks(struct svc_rqst *rqstp,
 	}
 
 	start += length;
-	length = head->rc_byte_len - start;
+	if (start > inline_len)
+		return -EINVAL;
+	length = inline_len - start;
 	return svc_rdma_copy_inline_range(rqstp, head, start, length);
 }
 
@@ -1187,8 +1196,12 @@ svc_rdma_read_multiple_chunks(struct svc_rqst *rqstp,
 static int svc_rdma_read_data_item(struct svc_rqst *rqstp,
 				   struct svc_rdma_recv_ctxt *head)
 {
-	return svc_rdma_build_read_chunk(rqstp, head,
-					 pcl_first_chunk(&head->rc_read_pcl));
+	struct svc_rdma_chunk *chunk = pcl_first_chunk(&head->rc_read_pcl);
+
+	if (chunk->ch_position > head->rc_saved_arg.head[0].iov_len)
+		return -EINVAL;
+
+	return svc_rdma_build_read_chunk(rqstp, head, chunk);
 }
 
 /**
@@ -1257,14 +1270,17 @@ static int svc_rdma_read_call_chunk(struct svc_rqst *rqstp,
 			pcl_first_chunk(&head->rc_call_pcl);
 	const struct svc_rdma_pcl *pcl = &head->rc_read_pcl;
 	struct svc_rdma_chunk *chunk, *next;
-	unsigned int start, length;
+	unsigned int call_len, start, length;
 	int ret;
 
 	if (pcl_is_empty(pcl))
 		return svc_rdma_build_read_chunk(rqstp, head, call_chunk);
 
+	call_len = call_chunk->ch_length;
 	start = 0;
 	chunk = pcl_first_chunk(pcl);
+	if (chunk->ch_position > call_len)
+		return -EINVAL;
 	length = chunk->ch_position;
 	ret = svc_rdma_read_chunk_range(rqstp, head, call_chunk,
 					start, length);
@@ -1281,6 +1297,10 @@ static int svc_rdma_read_call_chunk(struct svc_rqst *rqstp,
 			break;
 
 		start += length;
+		if (next->ch_position > call_len)
+			return -EINVAL;
+		if (head->rc_readbytes > next->ch_position)
+			return -EINVAL;
 		length = next->ch_position - head->rc_readbytes;
 		ret = svc_rdma_read_chunk_range(rqstp, head, call_chunk,
 						start, length);
@@ -1289,7 +1309,9 @@ static int svc_rdma_read_call_chunk(struct svc_rqst *rqstp,
 	}
 
 	start += length;
-	length = call_chunk->ch_length - start;
+	if (start > call_len)
+		return -EINVAL;
+	length = call_len - start;
 	return svc_rdma_read_chunk_range(rqstp, head, call_chunk,
 					 start, length);
 }

-- 
2.54.0