[PATCH AUTOSEL 4.20 039/304] sctp: Fix SKB list traversal in sctp_intl_store_ordered().

Sasha Levin
2019-01-28T17:49:53Z

From: "David S. Miller" <davem@davemloft.net>

[ Upstream commit e15e067d0656625c77c52b4e5f0cfbf0c0c3583f ]

Same change as made to sctp_intl_store_reasm().

To be fully correct, an iterator has an undefined value when something
like skb_queue_walk() naturally terminates.

This will actually matter when SKB queues are converted over to
list_head.

Formalize what this code ends up doing with the current
implementation.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sctp/stream_interleave.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/net/sctp/stream_interleave.c b/net/sctp/stream_interleave.c
index 0a78cdf86463..500449b72eca 100644
--- a/net/sctp/stream_interleave.c
+++ b/net/sctp/stream_interleave.c
@@ -383,7 +383,7 @@ static void sctp_intl_store_ordered(struct sctp_ulpq *ulpq,
struct sctp_ulpevent *event)
{
struct sctp_ulpevent *cevent;
- struct sk_buff *pos;
+ struct sk_buff *pos, *loc;

pos = skb_peek_tail(&ulpq->lobby);
if (!pos) {
@@ -403,18 +403,25 @@ static void sctp_intl_store_ordered(struct sctp_ulpq *ulpq,
return;
}

+ loc = NULL;
skb_queue_walk(&ulpq->lobby, pos) {
cevent = (struct sctp_ulpevent *)pos->cb;

- if (cevent->stream > event->stream)
+ if (cevent->stream > event->stream) {
+ loc = pos;
break;
-
+ }
if (cevent->stream == event->stream &&
- MID_lt(event->mid, cevent->mid))
+ MID_lt(event->mid, cevent->mid)) {
+ loc = pos;
break;
+ }
}

- __skb_queue_before(&ulpq->lobby, pos, sctp_event2skb(event));
+ if (!loc)
+ __skb_queue_tail(&ulpq->lobby, sctp_event2skb(event));
+ else
+ __skb_queue_before(&ulpq->lobby, loc, sctp_event2skb(event));
}

static void sctp_intl_retrieve_ordered(struct sctp_ulpq *ulpq,
--
2.19.1