netdev - Re: [PATCH v3 1/2] wifi: ath9k: fix races between ath9k_wmi_cmd and ath9k_wmi_ctrl

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Date: Tue, 22 Aug 2023 13:35:29 +0000 (UTC)
From: Kalle Valo <kvalo@...nel.org>
To: Fedor Pchelkin <pchelkin@...ras.ru>
Cc: Toke Høiland-Jørgensen <toke@...e.dk>,
 Fedor Pchelkin <pchelkin@...ras.ru>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 Senthil Balasubramanian <senthilkumar@...eros.com>,
 "John W. Linville" <linville@...driver.com>,
 Vasanthakumar Thiagarajan <vasanth@...eros.com>,
 Sujith <Sujith.Manoharan@...eros.com>, linux-wireless@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Alexey Khoroshilov <khoroshilov@...ras.ru>, lvc-project@...uxtesting.org,
 syzbot+f2cb6e0ffdb961921e4d@...kaller.appspotmail.com,
 Hillf Danton <hdanton@...a.com>
Subject: Re: [PATCH v3 1/2] wifi: ath9k: fix races between ath9k_wmi_cmd and
 ath9k_wmi_ctrl_rx

Fedor Pchelkin <pchelkin@...ras.ru> wrote:

> Currently, the synchronization between ath9k_wmi_cmd() and
> ath9k_wmi_ctrl_rx() is exposed to a race condition which, although being
> rather unlikely, can lead to invalid behaviour of ath9k_wmi_cmd().
> 
> Consider the following scenario:
> 
> CPU0                                    CPU1
> 
> ath9k_wmi_cmd(...)
>   mutex_lock(&wmi->op_mutex)
>   ath9k_wmi_cmd_issue(...)
>   wait_for_completion_timeout(...)
>   ---
>   timeout
>   ---
>                                         /* the callback is being processed
>                                          * before last_seq_id became zero
>                                          */
>                                         ath9k_wmi_ctrl_rx(...)
>                                           spin_lock_irqsave(...)
>                                           /* wmi->last_seq_id check here
>                                            * doesn't detect timeout yet
>                                            */
>                                           spin_unlock_irqrestore(...)
>   /* last_seq_id is zeroed to
>    * indicate there was a timeout
>    */
>   wmi->last_seq_id = 0
>   mutex_unlock(&wmi->op_mutex)
>   return -ETIMEDOUT
> 
> ath9k_wmi_cmd(...)
>   mutex_lock(&wmi->op_mutex)
>   /* the buffer is replaced with
>    * another one
>    */
>   wmi->cmd_rsp_buf = rsp_buf
>   wmi->cmd_rsp_len = rsp_len
>   ath9k_wmi_cmd_issue(...)
>     spin_lock_irqsave(...)
>     spin_unlock_irqrestore(...)
>   wait_for_completion_timeout(...)
>                                         /* the continuation of the
>                                          * callback left after the first
>                                          * ath9k_wmi_cmd call
>                                          */
>                                           ath9k_wmi_rsp_callback(...)
>                                             /* copying data designated
>                                              * to already timeouted
>                                              * WMI command into an
>                                              * inappropriate wmi_cmd_buf
>                                              */
>                                             memcpy(...)
>                                             complete(&wmi->cmd_wait)
>   /* awakened by the bogus callback
>    * => invalid return result
>    */
>   mutex_unlock(&wmi->op_mutex)
>   return 0
> 
> To fix this, update last_seq_id on timeout path inside ath9k_wmi_cmd()
> under the wmi_lock. Move ath9k_wmi_rsp_callback() under wmi_lock inside
> ath9k_wmi_ctrl_rx() so that the wmi->cmd_wait can be completed only for
> initially designated wmi_cmd call, otherwise the path would be rejected
> with last_seq_id check.
> 
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
> 
> Fixes: fb9987d0f748 ("ath9k_htc: Support for AR9271 chipset.")
> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
> Acked-by: Toke Høiland-Jørgensen <toke@...e.dk>
> Signed-off-by: Kalle Valo <quic_kvalo@...cinc.com>

2 patches applied to ath-next branch of ath.git, thanks.

b674fb513e2e wifi: ath9k: fix races between ath9k_wmi_cmd and ath9k_wmi_ctrl_rx
454994cfa9e4 wifi: ath9k: protect WMI command response buffer replacement with a lock

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20230425192607.18015-1-pchelkin@ispras.ru/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches