[PATCH 6.6 240/299] net/sched: act_mirred: dont override retval if we already lost the skb

Greg Kroah-Hartman
2024-02-27T13:57:56Z

From: Jakub Kicinski <kuba@kernel.org>

[ Upstream commit 166c2c8a6a4dc2e4ceba9e10cfe81c3e469e3210 ]

If we're redirecting the skb, and haven't called tcf_mirred_forward(),
yet, we need to tell the core to drop the skb by setting the retcode
to SHOT. If we have called tcf_mirred_forward(), however, the skb
is out of our hands and returning SHOT will lead to UaF.

Move the retval override to the error path which actually need it.

Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Fixes: e5cf1baf92cb ("act_mirred: use TC_ACT_REINSERT when possible")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/act_mirred.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index bab090bb5e80a..674f7ae356ca2 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -240,8 +240,7 @@ static int tcf_mirred_to_dev(struct sk_buff *skb, struct tcf_mirred *m,
if (unlikely(!(dev->flags & IFF_UP)) || !netif_carrier_ok(dev)) {
net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
dev->name);
- err = -ENODEV;
- goto out;
+ goto err_cant_do;
}

/* we could easily avoid the clone only if called by ingress and clsact;
@@ -253,10 +252,8 @@ static int tcf_mirred_to_dev(struct sk_buff *skb, struct tcf_mirred *m,
tcf_mirred_can_reinsert(retval);
if (!dont_clone) {
skb_to_send = skb_clone(skb, GFP_ATOMIC);
- if (!skb_to_send) {
- err = -ENOMEM;
- goto out;
- }
+ if (!skb_to_send)
+ goto err_cant_do;
}

want_ingress = tcf_mirred_act_wants_ingress(m_eaction);
@@ -293,15 +290,16 @@ static int tcf_mirred_to_dev(struct sk_buff *skb, struct tcf_mirred *m,
} else {
err = tcf_mirred_forward(at_ingress, want_ingress, skb_to_send);
}
-
- if (err) {
-out:
+ if (err)
tcf_action_inc_overlimit_qstats(&m->common);
- if (is_redirect)
- retval = TC_ACT_SHOT;
- }

return retval;
+
+err_cant_do:
+ if (is_redirect)
+ retval = TC_ACT_SHOT;
+ tcf_action_inc_overlimit_qstats(&m->common);
+ return retval;
}

TC_INDIRECT_SCOPE int tcf_mirred_act(struct sk_buff *skb,
--
2.43.0