[PATCH 6.0 025/190] wifi: mac80211: fix general-protection-fault in ieee80211_subif_start_xmit()

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From: Zhengchao Shao <shaozhengchao@xxxxxxxxxx>

[ Upstream commit 780854186946e0de2be192ee7fa5125666533b3a ]

When device is running and the interface status is changed, the gpf issue
is triggered. The problem triggering process is as follows:
Thread A:                           Thread B
ieee80211_runtime_change_iftype()   process_one_work()
    ...                                 ...
    ieee80211_do_stop()                 ...
    ...                                 ...
        sdata->bss = NULL               ...
        ...                             ieee80211_subif_start_xmit()
                                            ieee80211_multicast_to_unicast
                                    //!sdata->bss->multicast_to_unicast
                                      cause gpf issue

When the interface status is changed, the sending queue continues to send
packets. After the bss is set to NULL, the bss is accessed. As a result,
this causes a general-protection-fault issue.

The following is the stack information:
general protection fault, probably for non-canonical address
0xdffffc000000002f: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000178-0x000000000000017f]
Workqueue: mld mld_ifc_work
RIP: 0010:ieee80211_subif_start_xmit+0x25b/0x1310
Call Trace:
<TASK>
dev_hard_start_xmit+0x1be/0x990
__dev_queue_xmit+0x2c9a/0x3b60
ip6_finish_output2+0xf92/0x1520
ip6_finish_output+0x6af/0x11e0
ip6_output+0x1ed/0x540
mld_sendpack+0xa09/0xe70
mld_ifc_work+0x71c/0xdb0
process_one_work+0x9bf/0x1710
worker_thread+0x665/0x1080
kthread+0x2e4/0x3a0
ret_from_fork+0x1f/0x30
</TASK>

Fixes: f856373e2f31 ("wifi: mac80211: do not wake queues on a vif that is being stopped")
Reported-by: syzbot+c6e8fca81c294fd5620a@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Zhengchao Shao <shaozhengchao@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221026063959.177813-1-shaozhengchao@xxxxxxxxxx
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/mac80211/tx.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 13249e97a069..d2c4f9226f94 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -4379,6 +4379,11 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb,
 	if (likely(!is_multicast_ether_addr(eth->h_dest)))
 		goto normal;
 
+	if (unlikely(!ieee80211_sdata_running(sdata))) {
+		kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
+
 	if (unlikely(ieee80211_multicast_to_unicast(skb, dev))) {
 		struct sk_buff_head queue;
 
-- 
2.35.1






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