Re: [PATCH] net: ath9k: fix use-after-free in ath9k_hif_usb_rx_cb

[Pavel Skripkin <paskripkin@gmail.com>]

On 8/4/21 10:48 PM, Pavel Skripkin wrote:
> 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.
> 
> Also, I made whitespaces clean ups in *_STAT_* macros definitions
> to make checkpatch.pl happy.
> 
> Fixes: fb9987d0f748 ("ath9k_htc: Support for AR9271 chipset.")
> Reported-and-tested-by: syzbot+03110230a11411024147@syzkaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
> ---
> 
> Hi, ath9k maintainer/developers!
> 
> I know, that you do not like changes, that wasn't tested on real
> hardware. I really don't access to this one, so I'd like you to test it on
> real hardware piece, if you have one. At least, this patch was tested by
> syzbot [1]
> 
> [1] https://syzkaller.appspot.com/bug?id=6ead44e37afb6866ac0c7dd121b4ce07cb665f60
> 
> ---
>   drivers/net/wireless/ath/ath9k/htc.h          | 11 ++++++-----
>   drivers/net/wireless/ath/ath9k/htc_drv_init.c |  3 ++-
>   2 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath9k/htc.h b/drivers/net/wireless/ath/ath9k/htc.h
> index 0a1634238e67..c16b2a482e83 100644
> --- a/drivers/net/wireless/ath/ath9k/htc.h
> +++ b/drivers/net/wireless/ath/ath9k/htc.h
> @@ -326,11 +326,12 @@ 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 CAB_STAT_INC   priv->debug.tx_stats.cab_queued++
> +#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++)
>   
>   #define TX_QSTAT_INC(q) (priv->debug.tx_stats.queue_stats[q]++)
>   
> diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_init.c b/drivers/net/wireless/ath/ath9k/htc_drv_init.c
> index ff61ae34ecdf..07ac88fb1c57 100644
> --- a/drivers/net/wireless/ath/ath9k/htc_drv_init.c
> +++ b/drivers/net/wireless/ath/ath9k/htc_drv_init.c
> @@ -944,7 +944,6 @@ int ath9k_htc_probe_device(struct htc_target *htc_handle, struct device *dev,
>   	priv->hw = hw;
>   	priv->htc = htc_handle;
>   	priv->dev = dev;
> -	htc_handle->drv_priv = priv;
>   	SET_IEEE80211_DEV(hw, priv->dev);
>   
>   	ret = ath9k_htc_wait_for_target(priv);
> @@ -965,6 +964,8 @@ int ath9k_htc_probe_device(struct htc_target *htc_handle, struct device *dev,
>   	if (ret)
>   		goto err_init;
>   
> +	htc_handle->drv_priv = priv;
> +
>   	return 0;
>   
>   err_init:
> 

Added missing LKML in CC. Sorry for confusion.


With regards,
Pavel Skripkin