netdev - Re: [PATCH v3 1/2] ath9k: fix use-after-free in ath9k_hif_usb_rx

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Date:   Thu, 12 May 2022 14:49:57 +0200
From:   Toke Høiland-Jørgensen <toke@...e.dk>
To:     Pavel Skripkin <paskripkin@...il.com>,
        ath9k-devel@....qualcomm.com, kvalo@...nel.org,
        davem@...emloft.net, kuba@...nel.org, linville@...driver.com
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Pavel Skripkin <paskripkin@...il.com>,
        syzbot+03110230a11411024147@...kaller.appspotmail.com,
        syzbot+c6dde1f690b60e0b9fbe@...kaller.appspotmail.com
Subject: Re: [PATCH v3 1/2] ath9k: fix use-after-free in ath9k_hif_usb_rx_cb

Pavel Skripkin <paskripkin@...il.com> writes:

> Syzbot reported use-after-free Read in ath9k_hif_usb_rx_cb(). The
> problem was in incorrect htc_handle->drv_priv initialization.
>
> Probable call trace which can trigger use-after-free:
>
> ath9k_htc_probe_device()
>   /* htc_handle->drv_priv = priv; */
>   ath9k_htc_wait_for_target()      <--- Failed
>   ieee80211_free_hw()		   <--- priv pointer is freed
>
> <IRQ>
> ...
> ath9k_hif_usb_rx_cb()
>   ath9k_hif_usb_rx_stream()
>    RX_STAT_INC()		<--- htc_handle->drv_priv access
>
> In order to not add fancy protection for drv_priv we can move
> htc_handle->drv_priv initialization at the end of the
> ath9k_htc_probe_device() and add helper macro to make
> all *_STAT_* macros NULL save.
>
> Fixes: fb9987d0f748 ("ath9k_htc: Support for AR9271 chipset.")
> Reported-and-tested-by: syzbot+03110230a11411024147@...kaller.appspotmail.com
> Reported-and-tested-by: syzbot+c6dde1f690b60e0b9fbe@...kaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>

Could you link the original syzbot report in the commit message as well,
please? Also that 'tested-by' implies that syzbot run-tested this? How
does it do that; does it have ath9k_htc hardware?

> ---
>
> Changes since v2:
> 	- My send-email script forgot, that mailing lists exist.
> 	  Added back all related lists
>
> Changes since v1:
> 	- Removed clean-ups and moved them to 2/2
>
> ---
>  drivers/net/wireless/ath/ath9k/htc.h          | 10 +++++-----
>  drivers/net/wireless/ath/ath9k/htc_drv_init.c |  3 ++-
>  2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath9k/htc.h b/drivers/net/wireless/ath/ath9k/htc.h
> index 6b45e63fae4b..141642e5e00d 100644
> --- a/drivers/net/wireless/ath/ath9k/htc.h
> +++ b/drivers/net/wireless/ath/ath9k/htc.h
> @@ -327,11 +327,11 @@ static inline struct ath9k_htc_tx_ctl *HTC_SKB_CB(struct sk_buff *skb)
>  }
>  
>  #ifdef CONFIG_ATH9K_HTC_DEBUGFS
> -
> -#define TX_STAT_INC(c) (hif_dev->htc_handle->drv_priv->debug.tx_stats.c++)
> -#define TX_STAT_ADD(c, a) (hif_dev->htc_handle->drv_priv->debug.tx_stats.c += a)
> -#define RX_STAT_INC(c) (hif_dev->htc_handle->drv_priv->debug.skbrx_stats.c++)
> -#define RX_STAT_ADD(c, a) (hif_dev->htc_handle->drv_priv->debug.skbrx_stats.c += a)
> +#define __STAT_SAVE(expr) (hif_dev->htc_handle->drv_priv ? (expr) : 0)
> +#define TX_STAT_INC(c) __STAT_SAVE(hif_dev->htc_handle->drv_priv->debug.tx_stats.c++)
> +#define TX_STAT_ADD(c, a) __STAT_SAVE(hif_dev->htc_handle->drv_priv->debug.tx_stats.c += a)
> +#define RX_STAT_INC(c) __STAT_SAVE(hif_dev->htc_handle->drv_priv->debug.skbrx_stats.c++)
> +#define RX_STAT_ADD(c, a) __STAT_SAVE(hif_dev->htc_handle->drv_priv->debug.skbrx_stats.c += a)
>  #define CAB_STAT_INC   priv->debug.tx_stats.cab_queued++

s/SAVE/SAFE/ here and in the next patch (and the commit message).

-Toke