strparser: Fix incorrect strp->need_bytes value.

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@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 4 deletions

diff --git a/net/strparser/strparser.c b/net/strparser/strparser.c
index b9283ce5cd85..805b139756db 100644
--- a/net/strparser/strparser.c
+++ b/net/strparser/strparser.c
@@ -296,9 +296,9 @@ static int __strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
                                         strp_start_timer(strp, timeo);
                                 }
 
+                                stm->accum_len += cand_len;
                                 strp->need_bytes = stm->strp.full_len -
                                                        stm->accum_len;
-                                stm->accum_len += cand_len;
                                 stm->early_eaten = cand_len;
                                 STRP_STATS_ADD(strp->stats.bytes, cand_len);
                                 desc->count = 0; /* Stop reading socket */
@@ -321,6 +321,7 @@ static int __strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
                 /* Hurray, we have a new message! */
                 cancel_delayed_work(&strp->msg_timer_work);
                 strp->skb_head = NULL;
+                strp->need_bytes = 0;
                 STRP_STATS_INCR(strp->stats.msgs);
 
                 /* Give skb to upper layer */
@@ -410,9 +411,7 @@ void strp_data_ready(struct strparser *strp)
                 return;
 
         if (strp->need_bytes) {
-                if (strp_peek_len(strp) >= strp->need_bytes)
-                        strp->need_bytes = 0;
-                else
+                if (strp_peek_len(strp) < strp->need_bytes)
                         return;
         }