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: Jianqi Ren jianqi.ren.cn@windriver.com Signed-off-by: He Zhe zhe.he@windriver.com --- Verified the build test --- net/sched/act_mirred.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c index 36395e5db3b4..24c70ba6eebc 100644 --- a/net/sched/act_mirred.c +++ b/net/sched/act_mirred.c @@ -259,13 +259,13 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a, dev = rcu_dereference_bh(m->tcfm_dev); if (unlikely(!dev)) { pr_notice_once("tc mirred: target device is gone\n"); - goto out; + goto err_cant_do; }

if (unlikely(!(dev->flags & IFF_UP)) || !netif_carrier_ok(dev)) { net_notice_ratelimited("tc mirred to Houston: device %s is down\n", dev->name); - goto out; + goto err_cant_do; }

/* we could easily avoid the clone only if called by ingress and clsact; @@ -279,7 +279,7 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a, if (!use_reinsert) { skb2 = skb_clone(skb, GFP_ATOMIC); if (!skb2) - goto out; + goto err_cant_do; }

want_ingress = tcf_mirred_act_wants_ingress(m_eaction); @@ -321,12 +321,16 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a, }

err = tcf_mirred_forward(want_ingress, skb2); - if (err) { -out: + if (err) tcf_action_inc_overlimit_qstats(&m->common); - if (tcf_mirred_is_act_redirect(m_eaction)) - retval = TC_ACT_SHOT; - } + __this_cpu_dec(mirred_nest_level); + + return retval; + +err_cant_do: + if (tcf_mirred_is_act_redirect(m_eaction)) + retval = TC_ACT_SHOT; + tcf_action_inc_overlimit_qstats(&m->common); __this_cpu_dec(mirred_nest_level);

return retval;