[PATCH net] sch_sfb: Also store skb len before calling child enqueue

[PATCH net] sch_sfb: Also store skb len before calling child enqueue

[Toke Høiland-Jørgensen]

Cong Wang noticed that the previous fix for sch_sfb accessing the queued
skb after enqueueing it to a child qdisc was incomplete: the SFB enqueue
function was also calling qdisc_qstats_backlog_inc() after enqueue, which
reads the pkt len from the skb cb field. Fix this by also storing the skb
len, and using the stored value to increment the backlog after enqueueing.

Fixes: 9efd23297cca ("sch_sfb: Don't assume the skb is still around after enqueueing to child")
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
---
 net/sched/sch_sfb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c
index 0d761f454ae8..2829455211f8 100644
--- a/net/sched/sch_sfb.c
+++ b/net/sched/sch_sfb.c
@@ -281,6 +281,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 {
 
 	struct sfb_sched_data *q = qdisc_priv(sch);
+	unsigned int len = qdisc_pkt_len(skb);
 	struct Qdisc *child = q->qdisc;
 	struct tcf_proto *fl;
 	struct sfb_skb_cb cb;
@@ -403,7 +404,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	memcpy(&cb, sfb_skb_cb(skb), sizeof(cb));
 	ret = qdisc_enqueue(skb, child, to_free);
 	if (likely(ret == NET_XMIT_SUCCESS)) {
-		qdisc_qstats_backlog_inc(sch, skb);
+		sch->qstats.backlog += len;
 		sch->q.qlen++;
 		increment_qlen(&cb, q);
 	} else if (net_xmit_drop_count(ret)) {
-- 
2.37.2

Re: [PATCH net] sch_sfb: Also store skb len before calling child enqueue

[Cong Wang]

On Mon, Sep 05, 2022 at 09:21:36PM +0200, Toke Høiland-Jørgensen wrote:
> Cong Wang noticed that the previous fix for sch_sfb accessing the queued
> skb after enqueueing it to a child qdisc was incomplete: the SFB enqueue
> function was also calling qdisc_qstats_backlog_inc() after enqueue, which
> reads the pkt len from the skb cb field. Fix this by also storing the skb
> len, and using the stored value to increment the backlog after enqueueing.
> 
> Fixes: 9efd23297cca ("sch_sfb: Don't assume the skb is still around after enqueueing to child")
> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

Acked-by: Cong Wang <cong.wang@bytedance.com>

Thanks.

Re: [PATCH net] sch_sfb: Also store skb len before calling child enqueue

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by Paolo Abeni <pabeni@redhat.com>:

On Mon,  5 Sep 2022 21:21:36 +0200 you wrote:
> Cong Wang noticed that the previous fix for sch_sfb accessing the queued
> skb after enqueueing it to a child qdisc was incomplete: the SFB enqueue
> function was also calling qdisc_qstats_backlog_inc() after enqueue, which
> reads the pkt len from the skb cb field. Fix this by also storing the skb
> len, and using the stored value to increment the backlog after enqueueing.
> 
> Fixes: 9efd23297cca ("sch_sfb: Don't assume the skb is still around after enqueueing to child")
> Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
> 
> [...]

Here is the summary with links:
  - [net] sch_sfb: Also store skb len before calling child enqueue
    https://git.kernel.org/netdev/net/c/2f09707d0c97

You are awesome, thank you!
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