Whenever a user issues an ets qdisc change command, transforming a drr class into a strict one, the ets code isn't checking whether that class was in the active list and removing it. This means that, if a user changes a strict class (which was in the active list) back to a drr one, that class will be added twice to the active list [1]. Doing so with the following commands: tc qdisc add dev lo root handle 1: ets bands 2 strict 1 tc qdisc add dev lo parent 1:2 handle 20: \ tbf rate 8bit burst 100b latency 1s tc filter add dev lo parent 1: basic classid 1:2 ping -c1 -W0.01 -s 56 127.0.0.1 tc qdisc change dev lo root handle 1: ets bands 2 strict 2 tc qdisc change dev lo root handle 1: ets bands 2 strict 1 ping -c1 -W0.01 -s 56 127.0.0.1 Will trigger the following splat with list debug turned on: [ 59.279014][ T365] ------------[ cut here ]------------ [ 59.279452][ T365] list_add double add: new=ffff88801d60e350, prev=ffff88801d60e350, next=ffff88801d60e2c0. [ 59.280153][ T365] WARNING: CPU: 3 PID: 365 at lib/list_debug.c:35 __list_add_valid_or_report+0x17f/0x220 [ 59.280860][ T365] Modules linked in: [ 59.281165][ T365] CPU: 3 UID: 0 PID: 365 Comm: tc Not tainted 6.18.0-rc7-00105-g7e9f13163c13-dirty #239 PREEMPT(voluntary) [ 59.281977][ T365] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 59.282391][ T365] RIP: 0010:__list_add_valid_or_report+0x17f/0x220 [ 59.282842][ T365] Code: 89 c6 e8 d4 b7 0d ff 90 0f 0b 90 90 31 c0 e9 31 ff ff ff 90 48 c7 c7 e0 a0 22 9f 48 89 f2 48 89 c1 4c 89 c6 e8 b2 b7 0d ff 90 <0f> 0b 90 90 31 c0 e9 0f ff ff ff 48 89 f7 48 89 44 24 10 4c 89 44 ... [ 59.288812][ T365] Call Trace: [ 59.289056][ T365] [ 59.289224][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.289546][ T365] ets_qdisc_change+0xd2b/0x1e80 [ 59.289891][ T365] ? __lock_acquire+0x7e7/0x1be0 [ 59.290223][ T365] ? __pfx_ets_qdisc_change+0x10/0x10 [ 59.290546][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.290898][ T365] ? __mutex_trylock_common+0xda/0x240 [ 59.291228][ T365] ? __pfx___mutex_trylock_common+0x10/0x10 [ 59.291655][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.291993][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.292313][ T365] ? trace_contention_end+0xc8/0x110 [ 59.292656][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.293022][ T365] ? srso_alias_return_thunk+0x5/0xfbef5 [ 59.293351][ T365] tc_modify_qdisc+0x63a/0x1cf0 Fix this by always checking and removing an ets class from the active list when changing it to strict. [1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/tree/net/sched/sch_ets.c?id=ce052b9402e461a9aded599f5b47e76bc727f7de#n663 Fixes: cd9b50adc6bb9 ("net/sched: ets: fix crash when flipping from 'strict' to 'quantum'") Acked-by: Jamal Hadi Salim Signed-off-by: Victor Nogueira --- net/sched/sch_ets.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/sched/sch_ets.c b/net/sched/sch_ets.c index ae46643e596d..306e046276d4 100644 --- a/net/sched/sch_ets.c +++ b/net/sched/sch_ets.c @@ -664,6 +664,10 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt, q->classes[i].deficit = quanta[i]; } } + for (i = q->nstrict; i < nstrict; i++) { + if (cl_is_active(&q->classes[i])) + list_del_init(&q->classes[i].alist); + } WRITE_ONCE(q->nstrict, nstrict); memcpy(q->prio2band, priomap, sizeof(priomap)); -- 2.51.0 Add a test case for a bug fixed by Jamal [1] and for scenario where an ets drr class is inserted into the active list twice. - Try to delete ets drr class' qdisc while still keeping it in the active list - Try to add ets class to the active list twice [1] https://lore.kernel.org/netdev/20251128151919.576920-1-jhs@mojatatu.com/ Acked-by: Jamal Hadi Salim Signed-off-by: Victor Nogueira --- .../tc-testing/tc-tests/infra/qdiscs.json | 78 +++++++++++++++++++ 1 file changed, 78 insertions(+) diff --git a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json index 47de27fd4f90..6a39640aa2a8 100644 --- a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json +++ b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json @@ -1033,5 +1033,83 @@ "teardown": [ "$TC qdisc del dev $DUMMY handle 1: root" ] + }, + { + "id": "6e4f", + "name": "Try to delete ets drr class' qdisc while still keeping it in the active list", + "category": [ + "qdisc", + "ets", + "tbf" + ], + "plugins": { + "requires": [ + "nsPlugin", + "scapyPlugin" + ] + }, + "setup": [ + "$IP link set dev $DUMMY up || true", + "$IP addr add 10.10.11.10/24 dev $DUMMY || true", + "$TC qdisc add dev $DUMMY root handle 1: ets bands 2 strict 1", + "$TC qdisc add dev $DUMMY parent 1:2 handle 20: tbf rate 8bit burst 100b latency 1s", + "$TC filter add dev $DUMMY parent 1: basic classid 1:2", + "ping -c2 -W0.01 -s 56 -I $DUMMY 10.10.11.11 || true", + "$TC qdisc change dev $DUMMY root handle 1: ets bands 2 strict 2", + "$TC qdisc change dev $DUMMY root handle 1: ets bands 1 strict 1" + ], + "cmdUnderTest": "ping -c1 -W0.01 -s 56 -I $DUMMY 10.10.11.11", + "expExitCode": "1", + "verifyCmd": "$TC -s -j qdisc ls dev $DUMMY root", + "matchJSON": [ + { + "kind": "ets", + "handle": "1:", + "bytes": 196, + "packets": 2 + } + ], + "teardown": [ + "$TC qdisc del dev $DUMMY root handle 1:" + ] + }, + { + "id": "0b8f", + "name": "Try to add ets class to the active list twice", + "category": [ + "qdisc", + "ets", + "tbf" + ], + "plugins": { + "requires": [ + "nsPlugin", + "scapyPlugin" + ] + }, + "setup": [ + "$IP link set dev $DUMMY up || true", + "$IP addr add 10.10.11.10/24 dev $DUMMY || true", + "$TC qdisc add dev $DUMMY root handle 1: ets bands 2 strict 1", + "$TC qdisc add dev $DUMMY parent 1:2 handle 20: tbf rate 8bit burst 100b latency 1s", + "$TC filter add dev $DUMMY parent 1: basic classid 1:2", + "ping -c2 -W0.01 -s 56 -I $DUMMY 10.10.11.11 || true", + "$TC qdisc change dev $DUMMY root handle 1: ets bands 2 strict 2", + "$TC qdisc change dev $DUMMY root handle 1: ets bands 2 strict 1" + ], + "cmdUnderTest": "ping -c1 -W0.01 -s 56 -I $DUMMY 10.10.11.11", + "expExitCode": "1", + "verifyCmd": "$TC -s -j qdisc ls dev $DUMMY root", + "matchJSON": [ + { + "kind": "ets", + "handle": "1:", + "bytes": 98, + "packets": 1 + } + ], + "teardown": [ + "$TC qdisc del dev $DUMMY root handle 1:" + ] } ] -- 2.51.0