From 734b41ff166263c364e89518eb46e52310eb070b Mon Sep 17 00:00:00 2001
From: Boris Burkov <borisb@fb.com>
Date: Fri, 21 Aug 2020 00:40:02 -0700
Subject: [PATCH] btrfs-progs: receive: support v2 send stream DATA tlv format

The new format privileges the BTRFS_SEND_A_DATA attribute by
guaranteeing it will always be the last attribute in any command that
needs it, and by implicitly encoding the data length as the difference
between the total command length in the command header and the sizes of
the rest of the attributes (and of course the tlv_type identifying the
DATA attribute). To parse the new stream, we must read the tlv_type and
if it is not DATA, we proceed normally, but if it is DATA, we don't
parse a tlv_len but simply compute the length.

In addition, we add some bounds checking when parsing each chunk of
data, as well as for the tlv_len itself.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Boris Burkov <boris@bur.io>
---
 common/send-stream.c | 36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/common/send-stream.c b/common/send-stream.c
index 421cd1bb..81a830d9 100644
--- a/common/send-stream.c
+++ b/common/send-stream.c
@@ -168,28 +168,44 @@ static int read_cmd(struct btrfs_send_stream *sctx)
 
 	pos = 0;
 	while (pos < cmd_len) {
-		struct btrfs_tlv_header *tlv_hdr;
 		u16 tlv_type;
-		u16 tlv_len;
 		struct btrfs_send_attribute *send_attr;
 
-		tlv_hdr = (struct btrfs_tlv_header *)data;
-		tlv_type = le16_to_cpu(tlv_hdr->tlv_type);
-		tlv_len = le16_to_cpu(tlv_hdr->tlv_len);
+		if (cmd_len - pos < sizeof(__le16)) {
+			error("send stream is truncated");
+			ret = -EINVAL;
+			goto out;
+		}
+		tlv_type = le16_to_cpu(*(__le16 *)data);
 
 		if (tlv_type == 0 || tlv_type > BTRFS_SEND_A_MAX) {
-			error("invalid tlv in cmd tlv_type = %hu, tlv_len = %hu",
-					tlv_type, tlv_len);
+			error("invalid tlv in cmd tlv_type = %hu", tlv_type);
 			ret = -EINVAL;
 			goto out;
 		}
 
 		send_attr = &sctx->cmd_attrs[tlv_type];
 		send_attr->tlv_type = tlv_type;
-		send_attr->tlv_len = tlv_len;
-		pos += sizeof(*tlv_hdr);
-		data += sizeof(*tlv_hdr);
 
+		pos += sizeof(tlv_type);
+		data += sizeof(tlv_type);
+		if (sctx->version >= 2 && tlv_type == BTRFS_SEND_A_DATA) {
+			send_attr->tlv_len = cmd_len - pos;
+		} else {
+			if (cmd_len - pos < sizeof(__le16)) {
+				error("send stream is truncated");
+				ret = -EINVAL;
+				goto out;
+			}
+			send_attr->tlv_len = le16_to_cpu(*(__le16 *)data);
+			pos += sizeof(__le16);
+			data += sizeof(__le16);
+		}
+		if (cmd_len - pos < send_attr->tlv_len) {
+			error("send stream is truncated");
+			ret = -EINVAL;
+			goto out;
+		}
 		send_attr->data = data;
 		pos += send_attr->tlv_len;
 		data += send_attr->tlv_len;
-- 
2.35.1