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:

quoted

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 <redacted>
---

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