6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Martin Ottens <martin.ottens@xxxxxx>
[ Upstream commit 1596a135e3180c92e42dd1fbcad321f4fb3e3b17 ]
When the length of a GSO packet in the tbf qdisc is larger than the burst
size configured the packet will be segmented by the tbf_segment function.
Whenever this function is used to enqueue SKBs, the backlog statistic of
the tbf is not increased correctly. This can lead to underflows of the
'backlog' byte-statistic value when these packets are dequeued from tbf.
Reproduce the bug:
Ensure that the sender machine has GSO enabled. Configured the tbf on
the outgoing interface of the machine as follows (burstsize = 1 MTU):
$ tc qdisc add dev <oif> root handle 1: tbf rate 50Mbit burst 1514 latency 50ms
Send bulk TCP traffic out via this interface, e.g., by running an iPerf3
client on this machine. Check the qdisc statistics:
$ tc -s qdisc show dev <oif>
The 'backlog' byte-statistic has incorrect values while traffic is
transferred, e.g., high values due to u32 underflows. When the transfer
is stopped, the value is != 0, which should never happen.
This patch fixes this bug by updating the statistics correctly, even if
single SKBs of a GSO SKB cannot be enqueued.
Fixes: e43ac79a4bc6 ("sch_tbf: segment too big GSO packets")
Signed-off-by: Martin Ottens <martin.ottens@xxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://patch.msgid.link/20241125174608.1484356-1-martin.ottens@xxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
net/sched/sch_tbf.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index f1d09183ae632..dc26b22d53c73 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -208,7 +208,7 @@ static int tbf_segment(struct sk_buff *skb, struct Qdisc *sch,
struct tbf_sched_data *q = qdisc_priv(sch);
struct sk_buff *segs, *nskb;
netdev_features_t features = netif_skb_features(skb);
- unsigned int len = 0, prev_len = qdisc_pkt_len(skb);
+ unsigned int len = 0, prev_len = qdisc_pkt_len(skb), seg_len;
int ret, nb;
segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
@@ -219,21 +219,27 @@ static int tbf_segment(struct sk_buff *skb, struct Qdisc *sch,
nb = 0;
skb_list_walk_safe(segs, segs, nskb) {
skb_mark_not_on_list(segs);
- qdisc_skb_cb(segs)->pkt_len = segs->len;
- len += segs->len;
+ seg_len = segs->len;
+ qdisc_skb_cb(segs)->pkt_len = seg_len;
ret = qdisc_enqueue(segs, q->qdisc, to_free);
if (ret != NET_XMIT_SUCCESS) {
if (net_xmit_drop_count(ret))
qdisc_qstats_drop(sch);
} else {
nb++;
+ len += seg_len;
}
}
sch->q.qlen += nb;
- if (nb > 1)
+ sch->qstats.backlog += len;
+ if (nb > 0) {
qdisc_tree_reduce_backlog(sch, 1 - nb, prev_len - len);
- consume_skb(skb);
- return nb > 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
+ consume_skb(skb);
+ return NET_XMIT_SUCCESS;
+ }
+
+ kfree_skb(skb);
+ return NET_XMIT_DROP;
}
static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
--
2.43.0
