rtlwifi: Fix a double free in _rtl_usb_tx_urb_setup()

Seven years ago we tried to fix a leak but actually introduced a double
free instead.  It was an understandable mistake because the code was a
bit confusing and the free was done in the wrong place.  The "skb"
pointer is freed in both _rtl_usb_tx_urb_setup() and _rtl_usb_transmit().
The free belongs _rtl_usb_transmit() instead of _rtl_usb_tx_urb_setup()
and I've cleaned the code up a bit to hopefully make it more clear.

Fixes: 36ef0b473fbf ("rtlwifi: usb: add missing freeing of skbuff")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200513093951.GD347693@mwanda

diff --git a/drivers/net/wireless/realtek/rtlwifi/usb.c b/drivers/net/wireless/realtek/rtlwifi/usb.c
index 348b0072cdd698f25b495da1b580547c59321e8a..c66c6dc003783a6417c6d3a97553527e553e7d6e 100644 (file)
--- a/drivers/net/wireless/realtek/rtlwifi/usb.c
+++ b/drivers/net/wireless/realtek/rtlwifi/usb.c
@@ -881,10 +881,8 @@ static struct urb *_rtl_usb_tx_urb_setup(struct ieee80211_hw *hw,
 
        WARN_ON(NULL == skb);
        _urb = usb_alloc_urb(0, GFP_ATOMIC);
-       if (!_urb) {
-               kfree_skb(skb);
+       if (!_urb)
                return NULL;
-       }
        _rtl_install_trx_info(rtlusb, skb, ep_num);
        usb_fill_bulk_urb(_urb, rtlusb->udev, usb_sndbulkpipe(rtlusb->udev,
                          ep_num), skb->data, skb->len, _rtl_tx_complete, skb);
@@ -898,7 +896,6 @@ static void _rtl_usb_transmit(struct ieee80211_hw *hw, struct sk_buff *skb,
        struct rtl_usb *rtlusb = rtl_usbdev(rtl_usbpriv(hw));
        u32 ep_num;
        struct urb *_urb = NULL;
-       struct sk_buff *_skb = NULL;
 
        WARN_ON(NULL == rtlusb->usb_tx_aggregate_hdl);
        if (unlikely(IS_USB_STOP(rtlusb))) {
@@ -907,8 +904,7 @@ static void _rtl_usb_transmit(struct ieee80211_hw *hw, struct sk_buff *skb,
                return;
        }
        ep_num = rtlusb->ep_map.ep_mapping[qnum];
-       _skb = skb;
-       _urb = _rtl_usb_tx_urb_setup(hw, _skb, ep_num);
+       _urb = _rtl_usb_tx_urb_setup(hw, skb, ep_num);
        if (unlikely(!_urb)) {
                pr_err("Can't allocate urb. Drop skb!\n");
                kfree_skb(skb);