RE: [PATCH net,v2] wifi: mac80211: fix general-protection-fault in ieee80211_subif_start_xmit()

[Ping-Ke Shih <pkshih@realtek.com>]

> -----Original Message-----
> From: Zhengchao Shao <shaozhengchao@huawei.com>
> Sent: Wednesday, October 26, 2022 10:47 AM
> To: linux-wireless@vger.kernel.org; netdev@vger.kernel.org; johannes@sipsolutions.net;
> davem@davemloft.net; edumazet@google.com; kuba@kernel.org; pabeni@redhat.com
> Cc: toke@kernel.org; alexander@wetzel-home.de; nbd@nbd.name; weiyongjun1@huawei.com;
> yuehaibing@huawei.com; shaozhengchao@huawei.com
> Subject: [PATCH net,v2] wifi: mac80211: fix general-protection-fault in ieee80211_subif_start_xmit()
> 
> 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@syzkaller.appspotmail.com
> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> ---
>  net/mac80211/tx.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
> index a364148149f9..c38485f39d2b 100644
> --- a/net/mac80211/tx.c
> +++ b/net/mac80211/tx.c
> @@ -4418,6 +4418,11 @@ 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;
> +        }
> +

The indent looks odd. It seems like you use spaces instead of tabs?

>  	if (unlikely(ieee80211_multicast_to_unicast(skb, dev))) {
>  		struct sk_buff_head queue;
> 
> --
> 2.17.1
> 
> 
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