[PATCH net v2 1/2] net: team: stop reusing skb after queue override

[Weiming Shi]

A nonzero dev_queue_xmit() result does not return ownership of the skb.
When an override port's qdisc drops it, the queue override helper used to
try another port or the mode transmit op with the freed skb.

Return the handoff decision separately from transmit success. Select only
the first override port under RCU and stop after handing it the skb,
regardless of the lower transmit result. Keep the existing success and
drop accounting.

  BUG: KASAN: slab-use-after-free in sk_skb_reason_drop
  Write of size 4 by task poc/5040
  sk_skb_reason_drop (net/core/skbuff.c:1240)
  dev_kfree_skb_any_reason (net/core/dev.c:3470)
  ab_transmit (drivers/net/team/team_mode_activebackup.c:49)
  team_xmit (drivers/net/team/team_core.c:1849)
  __dev_direct_xmit (net/core/dev.c:4934)
  Freed by task 5040:
  __tcf_kfree_skb_list (net/sched/sch_generic.c:43)
  __dev_queue_xmit (net/core/dev.c:4831)
  team_xmit (drivers/net/team/team_core.c:1846)
  Kernel panic - not syncing: KASAN: panic_on_warn set ...

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 8ff5105a2b9d ("team: add support for queue override by setting queue_id for port")
Reported-by: <co+2cf741c3005abc20@xxxxxxx>
Assisted-by: LLM
Signed-off-by: Weiming Shi <bestswngs@xxxxxxxxx>
---
 drivers/net/team/team_core.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/net/team/team_core.c b/drivers/net/team/team_core.c
index feaa75fbf8fc2..3bf7c80f1d8e5 100644
--- a/drivers/net/team/team_core.c
+++ b/drivers/net/team/team_core.c
@@ -820,7 +820,8 @@ static struct list_head *__team_get_qom_list(struct team *team, u16 queue_id)
 /*
  * note: already called with rcu_read_lock
  */
-static bool team_queue_override_transmit(struct team *team, struct sk_buff *skb)
+static bool team_queue_override_transmit(struct team *team, struct sk_buff *skb,
+					 bool *tx_success)
 {
 	struct list_head *qom_list;
 	struct team_port *port;
@@ -828,11 +829,11 @@ static bool team_queue_override_transmit(struct team *team, struct sk_buff *skb)
 	if (!team->queue_override_enabled || !skb->queue_mapping)
 		return false;
 	qom_list = __team_get_qom_list(team, skb->queue_mapping);
-	list_for_each_entry_rcu(port, qom_list, qom_list) {
-		if (!team_dev_queue_xmit(team, port, skb))
-			return true;
-	}
-	return false;
+	port = list_first_or_null_rcu(qom_list, struct team_port, qom_list);
+	if (!port)
+		return false;
+	*tx_success = !team_dev_queue_xmit(team, port, skb);
+	return true;
 }
 
 static void __team_queue_override_port_del(struct team *team,
@@ -1864,8 +1865,7 @@ static netdev_tx_t team_xmit(struct sk_buff *skb, struct net_device *dev)
 	bool tx_success;
 	unsigned int len = skb->len;
 
-	tx_success = team_queue_override_transmit(team, skb);
-	if (!tx_success)
+	if (!team_queue_override_transmit(team, skb, &tx_success))
 		tx_success = READ_ONCE(team->ops.transmit)(team, skb);
 	if (tx_success) {
 		struct team_pcpu_stats *pcpu_stats;
-- 
2.55.0