[PATCH net v2 1/2] net/sched: act_mirred: Fix leak when redirecting to self on egress
From: Jamal Hadi Salim <jhs@mojatatu.com>
Date: 2026-01-01 13:56:26
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
Whenever a mirred redirect to self on egress happens, mirred allocates a
new skb (skb_to_send). The loop to self check was done after that
allocation, but was not freeing the newly allocated skb, causing a leak.
Fix this by moving the if-statement to before the allocation of the new
skb.
The issue was found by running the accompanying tdc test in 2/2
with config kmemleak enabled.
After a few minutes the kmemleak thread ran and reported the leak coming from
mirred.
Fixes: 1d856251a009 ("net/sched: act_mirred: fix loop detection")
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
---
net/sched/act_mirred.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 4a945ea00197..5ae2f01704ae 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c@@ -266,11 +266,22 @@ static int tcf_mirred_to_dev(struct sk_buff *skb, struct tcf_mirred *m, goto err_cant_do; } + want_ingress = tcf_mirred_act_wants_ingress(m_eaction); + + at_ingress = skb_at_tc_ingress(skb); + if (dev == skb->dev && want_ingress == at_ingress) { + pr_notice_once("tc mirred: Loop (%s:%s --> %s:%s)\n", + netdev_name(skb->dev), + at_ingress ? "ingress" : "egress", + netdev_name(dev), + want_ingress ? "ingress" : "egress"); + goto err_cant_do; + } + /* we could easily avoid the clone only if called by ingress and clsact; * since we can't easily detect the clsact caller, skip clone only for * ingress - that covers the TC S/W datapath. */ - at_ingress = skb_at_tc_ingress(skb); dont_clone = skb_at_tc_ingress(skb) && is_redirect && tcf_mirred_can_reinsert(retval); if (!dont_clone) {
@@ -279,17 +290,6 @@ static int tcf_mirred_to_dev(struct sk_buff *skb, struct tcf_mirred *m, goto err_cant_do; } - want_ingress = tcf_mirred_act_wants_ingress(m_eaction); - - if (dev == skb->dev && want_ingress == at_ingress) { - pr_notice_once("tc mirred: Loop (%s:%s --> %s:%s)\n", - netdev_name(skb->dev), - at_ingress ? "ingress" : "egress", - netdev_name(dev), - want_ingress ? "ingress" : "egress"); - goto err_cant_do; - } - /* All mirred/redirected skbs should clear previous ct info */ nf_reset_ct(skb_to_send); if (want_ingress && !at_ingress) /* drop dst for egress -> ingress */
--
2.34.1