From: Jamal Hadi Salim <jhs@mojatatu.com> mainline inclusion from mainline-v7.2-rc2 commit e5b811fe793166aecc59b085c1b7c31262ef2316 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/17369 CVE: CVE-2026-72390 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The teql master->slaves singly linked list is not protected against multiple writes. It can be mod'ed concurently from teql_master_xmit(), teql_dequeue(), teql_init() and teql_destroy() without holding any list lock or RCU protection. zdi-disclosures@trendmicro.com has demonstrated that the qdisc is freed after an RCU grace period, but teql_master_xmit() running on another CPU can still hold a stale pointer into the list, resulting in a slab-use-after-free: BUG: KASAN: slab-use-after-free in teql_master_xmit+0xf0f/0x16b0 Read of size 8 at addr ffff888013fb0440 by task poc/332 Freed 512-byte region [ffff888013fb0400, ffff888013fb0600) (kmalloc-512) The fix? Add a per-master slaves_lock spinlock that serializes all mutations of master->slaves and the NEXT_SLAVE() links in teql_destroy() and teql_qdisc_init(). teql_master_xmit() also takes the same slaves_lock around those updates. Annotate master->slaves and the per-slave ->next pointer with __rcu and use the appropriate RCU accessors everywhere they are touched: rcu_assign_pointer() on the writer side (under slaves_lock), rcu_dereference_protected() for the writer-side loads (also under slaves_lock), rcu_dereference_bh() for the loads in teql_master_xmit() and rtnl_dereference() for the loads in teql_master_open()/teql_master_mtu(), which run under RTNL. Pair this with rcu_read_lock_bh()/rcu_read_unlock_bh() around the list traversal in teql_master_xmit(), so that readers either observe a fully linked list or are deferred until the in-flight mutation completes. The two early-return paths in teql_master_xmit() are updated to release the RCU-bh read-side critical section before returning, since leaving it held would disable BH on that CPU for good. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: zdi-disclosures@trendmicro.com Tested-by: Victor Nogueira <victor@mojatatu.com> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com> Link: https://patch.msgid.link/20260628111229.669751-1-jhs@mojatatu.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> Conflicts: net/sched/sch_teql.c [commit 1eb2cded45b35 modifying teql_master_mtu() referenced WRITE_ ONCE(dev->mtu, new_mtu) which is absent in 5.10.] Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- net/sched/sch_teql.c | 125 +++++++++++++++++++++++++++++-------------- 1 file changed, 86 insertions(+), 39 deletions(-) diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c index d12035a4f7c9..1b58779e5d99 100644 --- a/net/sched/sch_teql.c +++ b/net/sched/sch_teql.c @@ -52,7 +52,8 @@ struct teql_master { struct Qdisc_ops qops; struct net_device *dev; - struct Qdisc *slaves; + struct Qdisc __rcu *slaves; + spinlock_t slaves_lock; /* serializes writes to ->slaves */ struct list_head master_list; unsigned long tx_bytes; unsigned long tx_packets; @@ -61,7 +62,7 @@ struct teql_master { }; struct teql_sched_data { - struct Qdisc *next; + struct Qdisc __rcu *next; struct teql_master *m; struct sk_buff_head q; }; @@ -101,7 +102,9 @@ teql_dequeue(struct Qdisc *sch) if (skb == NULL) { struct net_device *m = qdisc_dev(q); if (m) { - dat->m->slaves = sch; + spin_lock_bh(&dat->m->slaves_lock); + rcu_assign_pointer(dat->m->slaves, sch); + spin_unlock_bh(&dat->m->slaves_lock); netif_wake_queue(m); } } else { @@ -132,34 +135,49 @@ teql_destroy(struct Qdisc *sch) struct Qdisc *q, *prev; struct teql_sched_data *dat = qdisc_priv(sch); struct teql_master *master = dat->m; + struct netdev_queue *txq = NULL; + bool reset_master_queue = false; if (!master) return; - prev = master->slaves; + spin_lock_bh(&master->slaves_lock); + prev = rcu_dereference_protected(master->slaves, + lockdep_is_held(&master->slaves_lock)); if (prev) { do { - q = NEXT_SLAVE(prev); - if (q == sch) { - NEXT_SLAVE(prev) = NEXT_SLAVE(q); - if (q == master->slaves) { - master->slaves = NEXT_SLAVE(q); - if (q == master->slaves) { - struct netdev_queue *txq; - - txq = netdev_get_tx_queue(master->dev, 0); - master->slaves = NULL; - - dev_reset_queue(master->dev, - txq, NULL); - } - } - skb_queue_purge(&dat->q); - break; + struct Qdisc *head, *next; + + q = rcu_dereference_protected(NEXT_SLAVE(prev), + lockdep_is_held(&master->slaves_lock)); + if (q != sch) { + prev = q; + continue; } - } while ((prev = q) != master->slaves); + next = rcu_dereference_protected(NEXT_SLAVE(q), + lockdep_is_held(&master->slaves_lock)); + rcu_assign_pointer(NEXT_SLAVE(prev), next); + + head = rcu_dereference_protected(master->slaves, + lockdep_is_held(&master->slaves_lock)); + if (q == head) { + rcu_assign_pointer(master->slaves, next); + if (q == next) { + txq = netdev_get_tx_queue(master->dev, 0); + rcu_assign_pointer(master->slaves, NULL); + reset_master_queue = true; + } + } + skb_queue_purge(&dat->q); + break; + } while (prev != rcu_dereference_protected(master->slaves, + lockdep_is_held(&master->slaves_lock))); } + spin_unlock_bh(&master->slaves_lock); + + if (reset_master_queue) + dev_reset_queue(master->dev, txq, NULL); } static int teql_qdisc_init(struct Qdisc *sch, struct nlattr *opt, @@ -168,6 +186,7 @@ static int teql_qdisc_init(struct Qdisc *sch, struct nlattr *opt, struct net_device *dev = qdisc_dev(sch); struct teql_master *m = (struct teql_master *)sch->ops; struct teql_sched_data *q = qdisc_priv(sch); + struct Qdisc *first; if (dev->hard_header_len > m->dev->hard_header_len) return -EINVAL; @@ -184,7 +203,9 @@ static int teql_qdisc_init(struct Qdisc *sch, struct nlattr *opt, skb_queue_head_init(&q->q); - if (m->slaves) { + spin_lock_bh(&m->slaves_lock); + first = rcu_dereference_protected(m->slaves, lockdep_is_held(&m->slaves_lock)); + if (first) { if (m->dev->flags & IFF_UP) { if ((m->dev->flags & IFF_POINTOPOINT && !(dev->flags & IFF_POINTOPOINT)) || @@ -192,8 +213,10 @@ static int teql_qdisc_init(struct Qdisc *sch, struct nlattr *opt, !(dev->flags & IFF_BROADCAST)) || (m->dev->flags & IFF_MULTICAST && !(dev->flags & IFF_MULTICAST)) || - dev->mtu < m->dev->mtu) + dev->mtu < m->dev->mtu) { + spin_unlock_bh(&m->slaves_lock); return -EINVAL; + } } else { if (!(dev->flags&IFF_POINTOPOINT)) m->dev->flags &= ~IFF_POINTOPOINT; @@ -204,14 +227,17 @@ static int teql_qdisc_init(struct Qdisc *sch, struct nlattr *opt, if (dev->mtu < m->dev->mtu) m->dev->mtu = dev->mtu; } - q->next = NEXT_SLAVE(m->slaves); - NEXT_SLAVE(m->slaves) = sch; + rcu_assign_pointer(q->next, + rcu_dereference_protected(NEXT_SLAVE(first), + lockdep_is_held(&m->slaves_lock))); + rcu_assign_pointer(NEXT_SLAVE(first), sch); } else { - q->next = sch; - m->slaves = sch; + rcu_assign_pointer(q->next, sch); + rcu_assign_pointer(m->slaves, sch); m->dev->mtu = dev->mtu; m->dev->flags = (m->dev->flags&~FMASK)|(dev->flags&FMASK); } + spin_unlock_bh(&m->slaves_lock); return 0; } @@ -285,7 +311,9 @@ static netdev_tx_t teql_master_xmit(struct sk_buff *skb, struct net_device *dev) int subq = skb_get_queue_mapping(skb); struct sk_buff *skb_res = NULL; - start = master->slaves; + rcu_read_lock_bh(); + + start = rcu_dereference_bh(master->slaves); restart: nores = 0; @@ -316,10 +344,17 @@ static netdev_tx_t teql_master_xmit(struct sk_buff *skb, struct net_device *dev) netdev_start_xmit(skb, slave, slave_txq, false) == NETDEV_TX_OK) { __netif_tx_unlock(slave_txq); - master->slaves = NEXT_SLAVE(q); + spin_lock_bh(&master->slaves_lock); + if (rcu_dereference_protected(master->slaves, + lockdep_is_held(&master->slaves_lock)) == q) + rcu_assign_pointer(master->slaves, + rcu_dereference_protected(NEXT_SLAVE(q), + lockdep_is_held(&master->slaves_lock))); + spin_unlock_bh(&master->slaves_lock); netif_wake_queue(dev); master->tx_packets++; master->tx_bytes += length; + rcu_read_unlock_bh(); return NETDEV_TX_OK; } __netif_tx_unlock(slave_txq); @@ -328,14 +363,21 @@ static netdev_tx_t teql_master_xmit(struct sk_buff *skb, struct net_device *dev) busy = 1; break; case 1: - master->slaves = NEXT_SLAVE(q); + spin_lock_bh(&master->slaves_lock); + if (rcu_dereference_protected(master->slaves, + lockdep_is_held(&master->slaves_lock)) == q) + rcu_assign_pointer(master->slaves, + rcu_dereference_protected(NEXT_SLAVE(q), + lockdep_is_held(&master->slaves_lock))); + spin_unlock_bh(&master->slaves_lock); + rcu_read_unlock_bh(); return NETDEV_TX_OK; default: nores = 1; break; } __skb_pull(skb, skb_network_offset(skb)); - } while ((q = NEXT_SLAVE(q)) != start); + } while ((q = rcu_dereference_bh(NEXT_SLAVE(q))) != start); if (nores && skb_res == NULL) { skb_res = skb; @@ -344,29 +386,32 @@ static netdev_tx_t teql_master_xmit(struct sk_buff *skb, struct net_device *dev) if (busy) { netif_stop_queue(dev); + rcu_read_unlock_bh(); return NETDEV_TX_BUSY; } master->tx_errors++; drop: master->tx_dropped++; + rcu_read_unlock_bh(); dev_kfree_skb(skb); return NETDEV_TX_OK; } static int teql_master_open(struct net_device *dev) { - struct Qdisc *q; + struct Qdisc *q, *first; struct teql_master *m = netdev_priv(dev); int mtu = 0xFFFE; unsigned int flags = IFF_NOARP | IFF_MULTICAST; - if (m->slaves == NULL) + first = rtnl_dereference(m->slaves); + if (!first) return -EUNATCH; flags = FMASK; - q = m->slaves; + q = first; do { struct net_device *slave = qdisc_dev(q); @@ -388,7 +433,7 @@ static int teql_master_open(struct net_device *dev) flags &= ~IFF_BROADCAST; if (!(slave->flags&IFF_MULTICAST)) flags &= ~IFF_MULTICAST; - } while ((q = NEXT_SLAVE(q)) != m->slaves); + } while ((q = rtnl_dereference(NEXT_SLAVE(q))) != first); m->dev->mtu = mtu; m->dev->flags = (m->dev->flags&~FMASK) | flags; @@ -416,14 +461,15 @@ static void teql_master_stats64(struct net_device *dev, static int teql_master_mtu(struct net_device *dev, int new_mtu) { struct teql_master *m = netdev_priv(dev); - struct Qdisc *q; + struct Qdisc *q, *first; - q = m->slaves; + first = rtnl_dereference(m->slaves); + q = first; if (q) { do { if (new_mtu > qdisc_dev(q)->mtu) return -EINVAL; - } while ((q = NEXT_SLAVE(q)) != m->slaves); + } while ((q = rtnl_dereference(NEXT_SLAVE(q))) != first); } dev->mtu = new_mtu; @@ -443,6 +489,7 @@ static __init void teql_master_setup(struct net_device *dev) struct teql_master *master = netdev_priv(dev); struct Qdisc_ops *ops = &master->qops; + spin_lock_init(&master->slaves_lock); master->dev = dev; ops->priv_size = sizeof(struct teql_sched_data); -- 2.43.0