netdev - [PATCH AUTOSEL 4.19 601/671] net: netem: correct the parent's backlog when corrupted packet was dropped

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Date:   Thu, 16 Jan 2020 12:03:59 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Simon Horman <simon.horman@...ronome.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>,
        netem@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 601/671] net: netem: correct the parent's backlog when corrupted packet was dropped

From: Jakub Kicinski <jakub.kicinski@...ronome.com>

[ Upstream commit e0ad032e144731a5928f2d75e91c2064ba1a764c ]

If packet corruption failed we jump to finish_segs and return
NET_XMIT_SUCCESS. Seeing success will make the parent qdisc
increment its backlog, that's incorrect - we need to return
NET_XMIT_DROP.

Fixes: 6071bd1aa13e ("netem: Segment GSO packets on enqueue")
Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Reviewed-by: Simon Horman <simon.horman@...ronome.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/sched/sch_netem.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 7660aa5b80da..014a28d8dd4f 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -607,6 +607,8 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 		}
 		/* Parent qdiscs accounted for 1 skb of size @prev_len */
 		qdisc_tree_reduce_backlog(sch, -(nb - 1), -(len - prev_len));
+	} else if (!skb) {
+		return NET_XMIT_DROP;
 	}
 	return NET_XMIT_SUCCESS;
 }
-- 
2.20.1