[PATCH 4.9 68/74] strparser: Fix incorrect strp->need_bytes value.

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Doron Roberts-Kedes <doronrk@xxxxxx>


[ Upstream commit 9d0c75bf6e03d9bf80c55b0f677dc9b982958fd5 ]

strp_data_ready resets strp->need_bytes to 0 if strp_peek_len indicates
that the remainder of the message has been received. However,
do_strp_work does not reset strp->need_bytes to 0. If do_strp_work
completes a partial message, the value of strp->need_bytes will continue
to reflect the needed bytes of the previous message, causing
future invocations of strp_data_ready to return early if
strp->need_bytes is less than strp_peek_len. Resetting strp->need_bytes
to 0 in __strp_recv on handing a full message to the upper layer solves
this problem.

__strp_recv also calculates strp->need_bytes using stm->accum_len before
stm->accum_len has been incremented by cand_len. This can cause
strp->need_bytes to be equal to the full length of the message instead
of the full length minus the accumulated length. This, in turn, causes
strp_data_ready to return early, even when there is sufficient data to
complete the partial message. Incrementing stm->accum_len before using
it to calculate strp->need_bytes solves this problem.

Found while testing net/tls_sw recv path.

Fixes: 43a0c6751a322847 ("strparser: Stream parser for messages")
Signed-off-by: Doron Roberts-Kedes <doronrk@xxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/strparser/strparser.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/net/strparser/strparser.c
+++ b/net/strparser/strparser.c
@@ -285,9 +285,9 @@ static int strp_recv(read_descriptor_t *
 					strp_start_rx_timer(strp);
 				}
 
+				rxm->accum_len += cand_len;
 				strp->rx_need_bytes = rxm->strp.full_len -
 						       rxm->accum_len;
-				rxm->accum_len += cand_len;
 				rxm->early_eaten = cand_len;
 				STRP_STATS_ADD(strp->stats.rx_bytes, cand_len);
 				desc->count = 0; /* Stop reading socket */
@@ -310,6 +310,7 @@ static int strp_recv(read_descriptor_t *
 		/* Hurray, we have a new message! */
 		del_timer(&strp->rx_msg_timer);
 		strp->rx_skb_head = NULL;
+		strp->rx_need_bytes = 0;
 		STRP_STATS_INCR(strp->stats.rx_msgs);
 
 		/* Give skb to upper layer */
@@ -374,9 +375,7 @@ void strp_data_ready(struct strparser *s
 		return;
 
 	if (strp->rx_need_bytes) {
-		if (strp_peek_len(strp) >= strp->rx_need_bytes)
-			strp->rx_need_bytes = 0;
-		else
+		if (strp_peek_len(strp) < strp->rx_need_bytes)
 			return;
 	}