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 [Minor conflict resolved due to code context change.] Signed-off-by: Jianqi Ren jianqi.ren.cn@windriver.com Signed-off-by: He Zhe zhe.he@windriver.com --- v2: Fix the following issue net/sched/act_mirred.c:265:6: error: variable 'is_redirect' is used uninitialized whenever 'if' condition is true found by the following tuxmake (https://lore.kernel.org/stable/CA+G9fYu+FEZ-3ye30Hk2sk1+LFsw7iO5AHueUa9H1Ub=...) tuxmake --runtime podman --target-arch arm --toolchain clang-20 --kconfig allmodconfig LLVM=1 LLVM_IAS=1 The above command line couldn't pass for some other issue unrelated to this patch, but we're sure that the above "is_redirect" issue has been fixed. --- net/sched/act_mirred.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c index 91a19460cb57..07b9f8335f05 100644 --- a/net/sched/act_mirred.c +++ b/net/sched/act_mirred.c @@ -256,31 +256,31 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a,

m_mac_header_xmit = READ_ONCE(m->tcfm_mac_header_xmit); m_eaction = READ_ONCE(m->tcfm_eaction); + is_redirect = tcf_mirred_is_act_redirect(m_eaction); retval = READ_ONCE(m->tcf_action); 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; * since we can't easily detect the clsact caller, skip clone only for * ingress - that covers the TC S/W datapath. */ - is_redirect = tcf_mirred_is_act_redirect(m_eaction); at_ingress = skb_at_tc_ingress(skb); use_reinsert = at_ingress && is_redirect && tcf_mirred_can_reinsert(retval); 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); @@ -323,12 +323,16 @@ 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 (is_redirect) + retval = TC_ACT_SHOT; + tcf_action_inc_overlimit_qstats(&m->common); __this_cpu_dec(mirred_nest_level);

return retval;