6.8-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 0f022d32c3eca477fbf79a205243a6123ed0fe11 ]
When the mirred action is used on a classful egress qdisc and a packet is mirrored or redirected to self we hit a qdisc lock deadlock. See trace below.
[..... other info removed for brevity....] [ 82.890906] [ 82.890906] ============================================ [ 82.890906] WARNING: possible recursive locking detected [ 82.890906] 6.8.0-05205-g77fadd89fe2d-dirty #213 Tainted: G W [ 82.890906] -------------------------------------------- [ 82.890906] ping/418 is trying to acquire lock: [ 82.890906] ffff888006994110 (&sch->q.lock){+.-.}-{3:3}, at: __dev_queue_xmit+0x1778/0x3550 [ 82.890906] [ 82.890906] but task is already holding lock: [ 82.890906] ffff888006994110 (&sch->q.lock){+.-.}-{3:3}, at: __dev_queue_xmit+0x1778/0x3550 [ 82.890906] [ 82.890906] other info that might help us debug this: [ 82.890906] Possible unsafe locking scenario: [ 82.890906] [ 82.890906] CPU0 [ 82.890906] ---- [ 82.890906] lock(&sch->q.lock); [ 82.890906] lock(&sch->q.lock); [ 82.890906] [ 82.890906] *** DEADLOCK *** [ 82.890906] [..... other info removed for brevity....]
Example setup (eth0->eth0) to recreate tc qdisc add dev eth0 root handle 1: htb default 30 tc filter add dev eth0 handle 1: protocol ip prio 2 matchall \ action mirred egress redirect dev eth0
Another example(eth0->eth1->eth0) to recreate tc qdisc add dev eth0 root handle 1: htb default 30 tc filter add dev eth0 handle 1: protocol ip prio 2 matchall \ action mirred egress redirect dev eth1
tc qdisc add dev eth1 root handle 1: htb default 30 tc filter add dev eth1 handle 1: protocol ip prio 2 matchall \ action mirred egress redirect dev eth0
We fix this by adding an owner field (CPU id) to struct Qdisc set after root qdisc is entered. When the softirq enters it a second time, if the qdisc owner is the same CPU, the packet is dropped to break the loop.
Reported-by: Mingshuai Ren renmingshuai@huawei.com Closes: https://lore.kernel.org/netdev/20240314111713.5979-1-renmingshuai@huawei.com... Fixes: 3bcb846ca4cf ("net: get rid of spin_trylock() in net_tx_action()") Fixes: e578d9c02587 ("net: sched: use counter to break reclassify loops") Signed-off-by: Eric Dumazet edumazet@google.com Reviewed-by: Victor Nogueira victor@mojatatu.com Reviewed-by: Pedro Tammela pctammela@mojatatu.com Tested-by: Jamal Hadi Salim jhs@mojatatu.com Acked-by: Jamal Hadi Salim jhs@mojatatu.com Link: https://lore.kernel.org/r/20240415210728.36949-1-victor@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/sch_generic.h | 1 + net/core/dev.c | 6 ++++++ net/sched/sch_generic.c | 1 + 3 files changed, 8 insertions(+)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index cefe0c4bdae34..41ca14e81d55f 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -117,6 +117,7 @@ struct Qdisc { struct qdisc_skb_head q; struct gnet_stats_basic_sync bstats; struct gnet_stats_queue qstats; + int owner; unsigned long state; unsigned long state2; /* must be written under qdisc spinlock */ struct Qdisc *next_sched; diff --git a/net/core/dev.c b/net/core/dev.c index c9b8412f1c9d3..c365aa06f886f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3791,6 +3791,10 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, return rc; }
+ if (unlikely(READ_ONCE(q->owner) == smp_processor_id())) { + kfree_skb_reason(skb, SKB_DROP_REASON_TC_RECLASSIFY_LOOP); + return NET_XMIT_DROP; + } /* * Heuristic to force contended enqueues to serialize on a * separate lock before trying to get qdisc main lock. @@ -3830,7 +3834,9 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, qdisc_run_end(q); rc = NET_XMIT_SUCCESS; } else { + WRITE_ONCE(q->owner, smp_processor_id()); rc = dev_qdisc_enqueue(skb, q, &to_free, txq); + WRITE_ONCE(q->owner, -1); if (qdisc_run_begin(q)) { if (unlikely(contended)) { spin_unlock(&q->busylock); diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 9b3e9262040b6..a498b5d7c5d60 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -973,6 +973,7 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue, sch->enqueue = ops->enqueue; sch->dequeue = ops->dequeue; sch->dev_queue = dev_queue; + sch->owner = -1; netdev_hold(dev, &sch->dev_tracker, GFP_KERNEL); refcount_set(&sch->refcnt, 1);