linux-kernel - Re: [PATCH] net: ath9k: fix use-after-free in ath9k_hif_usb_rx

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Message-ID: <4119f4fa-31b0-66bc-a0e2-373b2e1c449e@gmail.com>
Date:   Tue, 31 Aug 2021 13:43:51 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     ath9k-devel@....qualcomm.com, kvalo@...eaurora.org,
        davem@...emloft.net, vasanth@...eros.com, senthilkumar@...eros.com
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        syzbot+03110230a11411024147@...kaller.appspotmail.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: ath9k: fix use-after-free in ath9k_hif_usb_rx_cb

On 8/4/21 10:57 PM, Pavel Skripkin wrote:
> 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@...kaller.appspotmail.com
>> Signed-off-by: Pavel Skripkin <paskripkin@...il.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.
> 
> 
Any chance to review this patch? Thanks




With regards,
Pavel Skripkin