[PATCH v3] wifi: ath9k: hif_usb: clean up skbs if ath9k_hif_usb_rx_stream() fails

[Fedor Pchelkin]

Syzkaller detected a memory leak of skbs in ath9k_hif_usb_rx_stream().
While processing skbs in ath9k_hif_usb_rx_stream(), the already allocated
skbs in skb_pool are not freed if ath9k_hif_usb_rx_stream() fails. If we
have an incorrect pkt_len or pkt_tag, the input skb is considered invalid
and dropped. All the associated packets already in skb_pool should be
dropped and freed. Added a comment describing this issue.

The patch also makes remain_skb NULL after being processed so that it
cannot be referenced after potential free. The initialization of hif_dev
fields which are associated with remain_skb (rx_remain_len,
rx_transfer_len and rx_pad_len) is moved after a new remain_skb is
allocated. 

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 6ce708f54cc8 ("ath9k: Fix out-of-bound memcpy in ath9k_hif_usb_rx_stream")
Fixes: 44b23b488d44 ("ath9k: hif_usb: Reduce indent 1 column")
Reported-by: syzbot+e9632e3eb038d93d6bc6@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Fedor Pchelkin <pchelkin@xxxxxxxxx>
Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
---
v1->v2: added Reported-by tag
v2->v3: added proper remain_skb processing, stat macro, comment 

 drivers/net/wireless/ath/ath9k/hif_usb.c | 31 +++++++++++++++++-------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
index 1a2e0c7eeb02..de6c0824c9ca 100644
--- a/drivers/net/wireless/ath/ath9k/hif_usb.c
+++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
@@ -561,11 +561,11 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
 			memcpy(ptr, skb->data, rx_remain_len);
 
 			rx_pkt_len += rx_remain_len;
-			hif_dev->rx_remain_len = 0;
 			skb_put(remain_skb, rx_pkt_len);
 
 			skb_pool[pool_index++] = remain_skb;
-
+			hif_dev->remain_skb = NULL;
+			hif_dev->rx_remain_len = 0;
 		} else {
 			index = rx_remain_len;
 		}
@@ -584,16 +584,21 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
 		pkt_len = get_unaligned_le16(ptr + index);
 		pkt_tag = get_unaligned_le16(ptr + index + 2);
 
+		/* It is supposed that if we have an invalid pkt_tag or
+		 * pkt_len then the whole input SKB is considered invalid
+		 * and dropped; the associated packets already in skb_pool
+		 * are dropped, too.
+		 */
 		if (pkt_tag != ATH_USB_RX_STREAM_MODE_TAG) {
 			RX_STAT_INC(hif_dev, skb_dropped);
-			return;
+			goto invalid_pkt;
 		}
 
 		if (pkt_len > 2 * MAX_RX_BUF_SIZE) {
 			dev_err(&hif_dev->udev->dev,
 				"ath9k_htc: invalid pkt_len (%x)\n", pkt_len);
 			RX_STAT_INC(hif_dev, skb_dropped);
-			return;
+			goto invalid_pkt;
 		}
 
 		pad_len = 4 - (pkt_len & 0x3);
@@ -605,11 +610,6 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
 
 		if (index > MAX_RX_BUF_SIZE) {
 			spin_lock(&hif_dev->rx_lock);
-			hif_dev->rx_remain_len = index - MAX_RX_BUF_SIZE;
-			hif_dev->rx_transfer_len =
-				MAX_RX_BUF_SIZE - chk_idx - 4;
-			hif_dev->rx_pad_len = pad_len;
-
 			nskb = __dev_alloc_skb(pkt_len + 32, GFP_ATOMIC);
 			if (!nskb) {
 				dev_err(&hif_dev->udev->dev,
@@ -617,6 +617,12 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
 				spin_unlock(&hif_dev->rx_lock);
 				goto err;
 			}
+
+			hif_dev->rx_remain_len = index - MAX_RX_BUF_SIZE;
+			hif_dev->rx_transfer_len =
+				MAX_RX_BUF_SIZE - chk_idx - 4;
+			hif_dev->rx_pad_len = pad_len;
+
 			skb_reserve(nskb, 32);
 			RX_STAT_INC(hif_dev, skb_allocated);
 
@@ -654,6 +660,13 @@ static void ath9k_hif_usb_rx_stream(struct hif_device_usb *hif_dev,
 				 skb_pool[i]->len, USB_WLAN_RX_PIPE);
 		RX_STAT_INC(hif_dev, skb_completed);
 	}
+	return;
+invalid_pkt:
+	for (i = 0; i < pool_index; i++) {
+		dev_kfree_skb_any(skb_pool[i]);
+		RX_STAT_INC(hif_dev, skb_dropped);
+	}
+	return;
 }
 
 static void ath9k_hif_usb_rx_cb(struct urb *urb)
-- 
2.34.1