[PATCH] Bluetooth: hci_uart: Add a local variable to store the result of h4_recv_buf()

[Myungho Jung]

In h4_recv(), if h4_recv_buf() returns error and h4_recv() is
asynchronously called again before setting rx_skb to NULL, ERR_PTR will
be dereferenced in h4_recv_buf(). Check return value in a local variable
before writing to rx_skb.

Reported-by: syzbot+017a32f149406df32703@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Myungho Jung <mhjungk@xxxxxxxxx>
---
 drivers/bluetooth/hci_h4.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
index fb97a3bf069b..fa30ec9cebd4 100644
--- a/drivers/bluetooth/hci_h4.c
+++ b/drivers/bluetooth/hci_h4.c
@@ -124,19 +124,22 @@ static const struct h4_recv_pkt h4_recv_pkts[] = {
 static int h4_recv(struct hci_uart *hu, const void *data, int count)
 {
 	struct h4_struct *h4 = hu->priv;
+	struct sk_buff *skb;
 
 	if (!test_bit(HCI_UART_REGISTERED, &hu->flags))
 		return -EUNATCH;
 
-	h4->rx_skb = h4_recv_buf(hu->hdev, h4->rx_skb, data, count,
-				 h4_recv_pkts, ARRAY_SIZE(h4_recv_pkts));
-	if (IS_ERR(h4->rx_skb)) {
-		int err = PTR_ERR(h4->rx_skb);
+	skb = h4_recv_buf(hu->hdev, h4->rx_skb, data, count,
+			  h4_recv_pkts, ARRAY_SIZE(h4_recv_pkts));
+	if (IS_ERR(skb)) {
+		int err = PTR_ERR(skb);
 		bt_dev_err(hu->hdev, "Frame reassembly failed (%d)", err);
 		h4->rx_skb = NULL;
 		return err;
 	}
 
+	h4->rx_skb = skb;
+
 	return count;
 }
 
-- 
2.17.1