[PATCH 1/2] wifi: mac80211: Update skb's NULL key in ieee80211_tx_h_select_key()

Remi Pommarel
2025-03-14T11:25:51Z

The ieee80211 skb control block key (set when skb was queued) could have
been removed before ieee80211_tx_dequeue() call. ieee80211_tx_dequeue()
already called ieee80211_tx_h_select_key() to get the current key, but
the latter do not update the key in skb control block in case it is
NULL. Because some drivers actually use this key in their TX callbacks
(e.g. ath1{1,2}k_mac_op_tx()) this could lead to the use after free
below:

BUG: KASAN: slab-use-after-free in ath11k_mac_op_tx+0x590/0x61c
Read of size 4 at addr ffffff803083c248 by task kworker/u16:4/1440

CPU: 3 UID: 0 PID: 1440 Comm: kworker/u16:4 Not tainted 6.13.0-ge128f627f404 #2
Hardware name: HW (DT)
Workqueue: bat_events batadv_send_outstanding_bcast_packet
Call trace:
show_stack+0x14/0x1c (C)
dump_stack_lvl+0x58/0x74
print_report+0x164/0x4c0
kasan_report+0xac/0xe8
__asan_report_load4_noabort+0x1c/0x24
ath11k_mac_op_tx+0x590/0x61c
ieee80211_handle_wake_tx_queue+0x12c/0x1c8
ieee80211_queue_skb+0xdcc/0x1b4c
ieee80211_tx+0x1ec/0x2bc
ieee80211_xmit+0x224/0x324
__ieee80211_subif_start_xmit+0x85c/0xcf8
ieee80211_subif_start_xmit+0xc0/0xec4
dev_hard_start_xmit+0xf4/0x28c
__dev_queue_xmit+0x6ac/0x318c
batadv_send_skb_packet+0x38c/0x4b0
batadv_send_outstanding_bcast_packet+0x110/0x328
process_one_work+0x578/0xc10
worker_thread+0x4bc/0xc7c
kthread+0x2f8/0x380
ret_from_fork+0x10/0x20

Allocated by task 1906:
kasan_save_stack+0x28/0x4c
kasan_save_track+0x1c/0x40
kasan_save_alloc_info+0x3c/0x4c
__kasan_kmalloc+0xac/0xb0
__kmalloc_noprof+0x1b4/0x380
ieee80211_key_alloc+0x3c/0xb64
ieee80211_add_key+0x1b4/0x71c
nl80211_new_key+0x2b4/0x5d8
genl_family_rcv_msg_doit+0x198/0x240
<...>

Freed by task 1494:
kasan_save_stack+0x28/0x4c
kasan_save_track+0x1c/0x40
kasan_save_free_info+0x48/0x94
__kasan_slab_free+0x48/0x60
kfree+0xc8/0x31c
kfree_sensitive+0x70/0x80
ieee80211_key_free_common+0x10c/0x174
ieee80211_free_keys+0x188/0x46c
ieee80211_stop_mesh+0x70/0x2cc
ieee80211_leave_mesh+0x1c/0x60
cfg80211_leave_mesh+0xe0/0x280
cfg80211_leave+0x1e0/0x244
<...>

Update SKB control block key even when key is NULL to avoid that.

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
---
net/mac80211/tx.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index a24636bda679..79c217c2f801 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -668,6 +668,12 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
} else if (ieee80211_is_data_present(hdr->frame_control) && tx->sta &&
test_sta_flag(tx->sta, WLAN_STA_USES_ENCRYPTION)) {
return TX_DROP;
+ } else {
+ /* Clear SKB CB key reference, ieee80211_tx_h_select_key()
+ * could have been called to update key info after its removal
+ * (e.g. by ieee80211_tx_dequeue()).
+ */
+ info->control.hw_key = NULL;
}

return TX_CONTINUE;
--
2.40.0