Fix a loop scenario of ethx:egress->ethx:egress Example setup to reproduce: tc qdisc add dev ethx root handle 1: drr tc filter add dev ethx parent 1: protocol ip prio 1 matchall \ action mirred egress redirect dev ethx Now ping out of ethx and you get a deadlock: [ 116.892898][ T307] ============================================ [ 116.893182][ T307] WARNING: possible recursive locking detected [ 116.893418][ T307] 6.18.0-rc6-01205-ge05021a829b8-dirty #204 Not tainted [ 116.893682][ T307] -------------------------------------------- [ 116.893926][ T307] ping/307 is trying to acquire lock: [ 116.894133][ T307] ffff88800c122908 (&sch->root_lock_key){+...}-{3:3}, at: __dev_queue_xmit+0x2210/0x3b50 [ 116.894517][ T307] [ 116.894517][ T307] but task is already holding lock: [ 116.894836][ T307] ffff88800c122908 (&sch->root_lock_key){+...}-{3:3}, at: __dev_queue_xmit+0x2210/0x3b50 [ 116.895252][ T307] [ 116.895252][ T307] other info that might help us debug this: [ 116.895608][ T307] Possible unsafe locking scenario: [ 116.895608][ T307] [ 116.895901][ T307] CPU0 [ 116.896057][ T307] ---- [ 116.896200][ T307] lock(&sch->root_lock_key); [ 116.896392][ T307] lock(&sch->root_lock_key); [ 116.896605][ T307] [ 116.896605][ T307] *** DEADLOCK *** [ 116.896605][ T307] [ 116.896864][ T307] May be due to missing lock nesting notation [ 116.896864][ T307] [ 116.897123][ T307] 6 locks held by ping/307: [ 116.897302][ T307] #0: ffff88800b4b0250 (sk_lock-AF_INET){+.+.}-{0:0}, at: raw_sendmsg+0xb20/0x2cf0 [ 116.897808][ T307] #1: ffffffff88c839c0 (rcu_read_lock){....}-{1:3}, at: ip_output+0xa9/0x600 [ 116.898138][ T307] #2: ffffffff88c839c0 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x2c6/0x1ee0 [ 116.898459][ T307] #3: ffffffff88c83960 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x200/0x3b50 [ 116.898782][ T307] #4: ffff88800c122908 (&sch->root_lock_key){+...}-{3:3}, at: __dev_queue_xmit+0x2210/0x3b50 [ 116.899132][ T307] #5: ffffffff88c83960 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x200/0x3b50 [ 116.899442][ T307] [ 116.899442][ T307] stack backtrace: [ 116.899667][ T307] CPU: 2 UID: 0 PID: 307 Comm: ping Not tainted 6.18.0-rc6-01205-ge05021a829b8-dirty #204 PREEMPT(voluntary) [ 116.899672][ T307] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 116.899675][ T307] Call Trace: [ 116.899678][ T307] [ 116.899680][ T307] dump_stack_lvl+0x6f/0xb0 [ 116.899688][ T307] print_deadlock_bug.cold+0xc0/0xdc [ 116.899695][ T307] __lock_acquire+0x11f7/0x1be0 [ 116.899704][ T307] lock_acquire+0x162/0x300 [ 116.899707][ T307] ? __dev_queue_xmit+0x2210/0x3b50 [ 116.899713][ T307] ? srso_alias_return_thunk+0x5/0xfbef5 [ 116.899717][ T307] ? stack_trace_save+0x93/0xd0 [ 116.899723][ T307] _raw_spin_lock+0x30/0x40 [ 116.899728][ T307] ? __dev_queue_xmit+0x2210/0x3b50 [ 116.899731][ T307] __dev_queue_xmit+0x2210/0x3b50 Fixes: 178ca30889a1 ("Revert "net/sched: Fix mirred deadlock on device recursion"") Tested-by: Victor Nogueira Signed-off-by: Jamal Hadi Salim --- net/sched/act_mirred.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c index f27b583def78..91c96cc625bd 100644 --- a/net/sched/act_mirred.c +++ b/net/sched/act_mirred.c @@ -281,6 +281,15 @@ static int tcf_mirred_to_dev(struct sk_buff *skb, struct tcf_mirred *m, 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 From: Victor Nogueira Add a test case that reproduces deadlock scenario where the user has a drr qdisc attached to root and has a mirred action that redirects to self on egress Signed-off-by: Victor Nogueira Acked-by: Jamal Hadi Salim --- .../tc-testing/tc-tests/actions/mirred.json | 46 +++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/tools/testing/selftests/tc-testing/tc-tests/actions/mirred.json b/tools/testing/selftests/tc-testing/tc-tests/actions/mirred.json index b73bd255ea36..da156feabcbf 100644 --- a/tools/testing/selftests/tc-testing/tc-tests/actions/mirred.json +++ b/tools/testing/selftests/tc-testing/tc-tests/actions/mirred.json @@ -1052,5 +1052,51 @@ "$TC qdisc del dev $DEV1 ingress_block 21 clsact", "$TC actions flush action mirred" ] + }, + { + "id": "7eba", + "name": "Redirect multiport: dummy egress -> dummy egress (Loop)", + "category": [ + "filter", + "mirred" + ], + "plugins": { + "requires": [ + "nsPlugin" + ] + }, + "setup": [ + "$IP link set dev $DUMMY up || true", + "$IP addr add 10.10.10.10/24 dev $DUMMY || true", + "$TC qdisc add dev $DUMMY handle 1: root drr", + "$TC filter add dev $DUMMY parent 1: protocol ip prio 10 matchall action mirred egress redirect dev $DUMMY index 1" + ], + "cmdUnderTest": "ping -c1 -W0.01 -I $DUMMY 10.10.10.1", + "expExitCode": "1", + "verifyCmd": "$TC -j -s actions get action mirred index 1", + "matchJSON": [ + { + "total acts": 0 + }, + { + "actions": [ + { + "order": 1, + "kind": "mirred", + "mirred_action": "redirect", + "direction": "egress", + "index": 1, + "stats": { + "packets": 1, + "overlimits": 1 + }, + "not_in_hw": true + } + ] + } + ], + "teardown": [ + "$TC qdisc del dev $DUMMY root" + ] } ] -- 2.34.1