linux-kernel - [PATCH 3.16 081/136] net: netem: correct the parent's backlog when corrupted packet was dropped

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Message-ID: <lsq.1576543535.451851386@decadent.org.uk>
Date:   Tue, 17 Dec 2019 00:46:55 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Jakub Kicinski" <jakub.kicinski@...ronome.com>,
        "Simon Horman" <simon.horman@...ronome.com>
Subject: [PATCH 3.16 081/136] net: netem: correct the parent's backlog
 when corrupted packet was dropped

3.16.80-rc1 review patch.  If anyone has any objections, please let me know.

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

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

commit e0ad032e144731a5928f2d75e91c2064ba1a764c upstream.

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: Ben Hutchings <ben@...adent.org.uk>
---
 net/sched/sch_netem.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -599,6 +599,8 @@ finish_segs:
 		}
 		/* 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;
 }