[PATCH wireless-drivers 2/3] mt76: usb: fix possible memory leak in mt76u_buf_free

[Lorenzo Bianconi]

Move q->ndesc initialization before the for loop in mt76u_alloc_rx
since otherwise allocated urbs will not be freed in mt76u_buf_free
Double-check scatterlist pointer in mt76u_buf_free

Fixes: b40b15e1521f ("mt76: add usb support to mt76 layer")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianc...@redhat.com>
---
 drivers/net/wireless/mediatek/mt76/usb.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/usb.c 
b/drivers/net/wireless/mediatek/mt76/usb.c
index b061263453d4..31c18ac1c94a 100644
--- a/drivers/net/wireless/mediatek/mt76/usb.c
+++ b/drivers/net/wireless/mediatek/mt76/usb.c
@@ -331,10 +331,16 @@ EXPORT_SYMBOL_GPL(mt76u_buf_alloc);
 void mt76u_buf_free(struct mt76u_buf *buf)
 {
        struct urb *urb = buf->urb;
+       struct scatterlist *sg;
        int i;
 
-       for (i = 0; i < urb->num_sgs; i++)
-               skb_free_frag(sg_virt(&urb->sg[i]));
+       for (i = 0; i < urb->num_sgs; i++) {
+               sg = &urb->sg[i];
+               if (!sg)
+                       continue;
+
+               skb_free_frag(sg_virt(sg));
+       }
        usb_free_urb(buf->urb);
 }
 EXPORT_SYMBOL_GPL(mt76u_buf_free);
@@ -540,7 +546,8 @@ static int mt76u_alloc_rx(struct mt76_dev *dev)
                nsgs = 1;
        }
 
-       for (i = 0; i < MT_NUM_RX_ENTRIES; i++) {
+       q->ndesc = MT_NUM_RX_ENTRIES;
+       for (i = 0; i < q->ndesc; i++) {
                err = mt76u_buf_alloc(dev, &q->entry[i].ubuf,
                                      nsgs, q->buf_size,
                                      SKB_WITH_OVERHEAD(q->buf_size),
@@ -548,7 +555,6 @@ static int mt76u_alloc_rx(struct mt76_dev *dev)
                if (err < 0)
                        return err;
        }
-       q->ndesc = MT_NUM_RX_ENTRIES;
 
        return mt76u_submit_rx_buffers(dev);
 }
-- 
2.20.1